Pan-cancer analysis of alternative splicing regulator heterogeneous nuclear ribonucleoproteins (hnRNPs) family and their prognostic potential

Hao Li1 | Jingwei Liu2 Shixuan Shen3 Di Dai1 Shitong Cheng1 Xiaolong Dong1

Liping Sun3 | Xiaolin Guo1 D

1Department of Laboratory Medicine, The First Affiliated Hospital of China Medical University, Shenyang, China

2Department of Anorectal Surgery, the First Affiliated Hospital of China Medical University, Shenyang, China

3Tumor Etiology and Screening Department of Cancer Institute and General Surgery, Key Laboratory of Cancer Etiology and Prevention, The First Hospital of China Medical University, China Medical University, Shenyang, China

Correspondence

Xiaolin Guo, Department of Laboratory Medicine, The First Affiliated Hospital of China Medical University, Shenyang 110011, China.

Email: xiaolinguo@cmu.edu.cn

Liping Sun, Tumor Etiology and Screening Department of Cancer Institute and General Surgery, The First Hospital of China Medical University, Key Laboratory of Cancer Etiology and Prevention, China Medical University, Shenyang 110011, China. Email: lpsun@cmu.edu.cn

Funding information

Ministry of Public Health and Sanitation, Grant/Award Number: 201402018; National Natural Science Foundation of China, Grant/ Award Number: 81902958; The Liaoning Key R&D Program, Grant/Award Number: 2020JH2/10300063; Cohort study on non- AIDS-related diseases in the First Affiliated Hospital of China Medical University, Grant/ Award Number: 2017ZX10202101-004-006

Abstract

As the most critical alternative splicing regulator, heterogeneous nuclear ribonu- cleoproteins (hnRNPs) have been reported to be implicated in various aspects of cancer. However, the comprehensive understanding of hnRNPs in cancer is still lack- ing. The molecular alterations and clinical relevance of hnRNP genes were system- atically analysed in 33 cancer types based on next-generation sequence data. The expression, mutation, copy number variation, functional pathways, immune cell cor- relations and prognostic value of hnRNPs were investigated across different cancer types. HNRNPA1 and HNRNPAB were highly expressed in most tumours. HNRNPM, HNRNPUL1, and HNRNPL showed high mutation frequencies, and most hnRNP genes were frequently mutated in uterine corpus endometrial carcinoma (UCEC). HNRNPA2B1 showed widespread copy number amplification across various cancer types. HNRNPs participated in cancer-related pathways including protein secretion, mitotic spindle, G2/M checkpoint, DNA repair, IL6/JAK/STAT3 signal and coagula- tion, of which hnRNP genes of HNRNPF, HNRNPH2, HNRNPU and HNRNPUL1 are more likely to be implicated. Significant correlation of hnRNP genes with T help cells, NK cells, CD8 positive T cells and neutrophils was identified. Most hnRNPs were as- sociated with worse survival of adrenocortical carcinoma (ACC), liver hepatocellular carcinoma (LIHC) and lung adenocarcinoma (LUAD), whereas hnRNPs predicted bet- ter prognosis in kidney renal clear cell carcinoma (KIRC) and thymoma (THYM). The prognosis analysis of KIRC suggested that hnRNPs gene cluster was significantly as- sociated with overall survival (HR = 0.5, 95% CI = 0.35-0.73, P = 0.003). These find- ings provide novel evidence for further investigation of hnRNPs in the development and therapy of cancer in the future.

KEYWORDS

alternative splicing, hnRNPs, pan-cancer

Li and Liu are contributed equally to this work.

@ 2020 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.

RNA splicing procedure removes introns and combines exons of pre-mature mRNA, which is essential for cellular homoeostasis, functional regulation, tissue development and species diversity.1,2 Almost each transcript derived from human genes undergoes di- verse patterns of alternative splicing (AS) including exclusion or in- clusion of “cassette” exons, changes of AS sites, intron retentions, alternative promoter or terminator, and mutually exclusive exons.3,4 Alternative splicing of pre-mRNA is responsible various aspects of biological processes and aberrant AS contribute to a series of disor- ders even cancer.5,6 Emerging evidence has demonstrated that can- cer cells hijack and alter AS process, thereby facilitating its growth and metastasis.7,8

As the most critical alternative splicing regulator, heteroge- neous nuclear ribonucleoproteins (hnRNPs) family are responsible for the maturation of pre-mRNAs into functional mRNAs as well as the stabilization of mRNA translocation.9,10 Through the RNA bind- ing domains (RBDs), hnRNPs accomplish the recognition of specific RNA sequences and control various biological processes of RNA function and metabolism.11,12 Mechanistically, hnRNPs constitute mRNA-protein 40S core complex via binding to RNA elements in- cluding exon and intron splicing regulators, which precisely control the alternative splicing of pre-mRNAs.13 Until now, approximately twenty key members of hnRNPs family have been identified includ- ing hnRNP A-U, which share common characteristics but differ in biological properties.14

Emerging evidence has suggested close relationship between hnRNPs and multiple malignant behaviours of cancer.15 For instance, hnRNP A1 modulates the alternative splicing of CDK2, thereby con- tributing to oral squamous cell carcinoma by altering cell cycle pro- gression.16 In pancreas cancer, hnRNP E1 cancer cell metastasis via controlling the alternative splicing of integrin §1, a membrane recep- tor involved in cell adhesion, immune response and metastatic diffu- sion of cancer cells.17 Studies have suggested that hnRNP A1, A2/B1 and K bind to the promoter of tumour suppressor Annexin-A7, which alters Annexin-A7 splicing patterns and leads to prostate cancer.18 In addition, hnRNP L has been found to regulate VEGFA mRNA trans- lation and induce apoptosis of cancer cells, thereby inhibiting the development of cancer.19

In spite of the current reports indicating the significant contri- bution of hnRNPs in carcinogenesis, our knowledge of the specific implication concerning hnRNPs still remains limited. Considering the increasing essential role of hnRNPs in cancer, it is of great interest to unravel the whole landscape of expression, mutation and copy number variation of alternative splicing regulator hn- RNPs family as well as their prognostic potential. Through analys- ing multiple levels of data from The Cancer Genome Atlas (TCGA) including 33 types of cancers, we described the specific implica- tion of alternative splicing regulator hnRNPs in various cancers in this study. It is anticipated that the comprehensive pan-cancer analysis could shed light on the way alternative splicing lead to cancer.

2 MATERIALS AND METHODS |

2.1 Collection of hnRNP genes

We collected 22 hnRNP genes from recently published review pa- pers. All these gene symbols were converted into Ensemble gene IDs and HGNC symbols by manually curated from GeneCards (https:// www.genecards.org/).

2.2 | Genome-wide omics data across 33 cancer types from next-generation sequence data

The results in our analysis were based upon omics datasets generated by TCGA Research Network (http://cancergenome.nih.gov/). We totally analysed 33 different TCGA projects, and each project represented a specific cancer type, including KIRC, kidney renal clear cell carcinoma; KIRP, kidney renal papillary cell carcinoma; KICH, kidney chromo- phobe; LGG, brain lower-grade glioma; GBM, glioblastoma multiforme; BRCA, breast cancer; LUSC, lung squamous cell carcinoma; LUAD, lung adenocarcinoma; READ, rectum adenocarcinoma; COAD, colon ade- nocarcinoma; UCS, uterine carcinosarcoma; UCEC, uterine corpus en- dometrial carcinoma; OV, ovarian serous cystadenocarcinoma; HNSC, head and neck squamous carcinoma; THCA, thyroid carcinoma; PRAD, prostate adenocarcinoma; STAD, stomach adenocarcinoma; SKCM, skin cutaneous melanoma; BLCA, bladder urothelial carcinoma; LIHC, liver hepatocellular carcinoma; CESC, cervical squamous cell carcinoma and endocervical adenocarcinoma; ACC, adrenocortical carcinoma; PCPG, pheochromocytoma and paraganglioma; SARC, sarcoma; LAML, acute myeloid leukaemia; PAAD, pancreatic adenocarcinoma; ESCA, oesophageal carcinoma; TGCT, testicular germ cell tumours; THYM, thymoma; MESO, mesothelioma; UVM, uveal melanoma; DLBC, lym- phoid neoplasm diffuse large B-cell lymphoma; CHOL, cholangiocar- cinoma. All of the TCGA data including TPM (Transcripts Per Kilobase Million) expression, copy number variation, mutation and clinical infor- mation (survival status, stages, grades, survival time) were download from UCSC XENA (https://xenabrowser.net/).

2.3 | Identification of differentially expressed genes

To identify the alternation of gene expression in each cancer type, we used the Deseq2 package in R to identify differentially expressed genes. Genes with adjusted P-values < 0.05 and at least twofold changes in expression were identified as differentially expressed genes in each cancer type.

2.4 | Protein-wide omics data across pan-cancer from protein expression data

The protein expression data of hnRNP genes were obtained from ‘The Human Protein Atlas’ database (https://www.proteinatlas.org/).

We totally analysed 20 cancer types on hnRNP genes protein ex- pression, including BRCA (breast cancer), carcinoid (carcinoid), CECA (cervical cancer), COCA (colorectal cancer), glioma (glioma), HNSC (head and neck cancer), LIHC (liver cancer), LUCA (lung cancer), lymphoma (lymphoma), melanoma (melanoma), OV (ovarian cancer), PACA (pancreatic cancer), RACA (renal cancer), SKCA (skin cancer), STCA (stomach cancer), TECA (testis cancer), THCA (thyroid can- cer), URCA (urothelial cancer), ENCA (endometrial cancer) and PRCA (prostate cancer).

2.5 Genome-wide mutation data across pan- cancer cell lines from CCLE datasets

Mutation frequency of hnRNP family genes in pan-cancer cell lines were obtained from Cancer Cell Line Encyclopedia (CCLE) datasets (https://portals.broadinstitute.org/ccle).

2.6 | Oncogenic pathway activity across cancer types

In order to calculate the activity of cancer hallmark-related path- ways, the TPM gene expression was subjected to gene set variation analysis (GSVA), which is a non-parametric unsupervised method for estimating variation of gene set enrichment through the samples of an expression dataset. To identify the hnRNP genes that were cor- related with activation or inhibition of certain pathway, we calcu- lated the Pearson correlation coefficient (PCC) between expression of hnRNP genes and pathway activity. The regulator-pathway pairs with |PCC|>0.3 and adjusted P-value < 0.05 were identified as sig- nificantly correlated hnRNP genes.

The major immune cells related genes were shown in Table S1. In order to explore the correlation between hnRNP genes and immune-related genes, we calculated the Spearman correlation coefficient (SCC) between expression of hnRNP genes and im- mune-related genes. The regulator-pathway pairs with |PCC|>0.3 and adjusted P-value < 0.05 were identified as significantly corre- lated hnRNP genes.

2.8 | Clinical significance of hnRNP genes

To explore whether the expression of hnRNP genes was associated with patient survival, we divided all the patients into two groups based on the median expression of each hnRNP gene. The log-rank test was used to test the different survival rates between the two groups. The P-values < 0.05 were considered as statistical significance.

|

3 RESULTS

3.1 Expression profile of hnRNP genes across different cancer types

A total of 22 hnRNP genes were identified after searching the pub- lished review papers, the information of which was summarized in Table S1. Using the count data of TCGA, we described the differential expression of these genes across different cancer types. As shown in Figure 1A, hnRNP genes demonstrated heterogeneous distributions in different cancer types: HNRNPA1 and HNRNPAB were highly ex- pressed in most tumours; HNRNPA1P33 expression was increased in COAD, READ and LUAD whereas decreased in CHOL, PRAD and BLCA. The detailed LogFC changes were listed in Table S2. Next, we visualized the differential expression of HNRNPAB in each can- cer (Figure 1B). Based on the immunohischemistry results of Protein Atlas database, we showed the protein expression of hnRNP genes in various cancer types (Figure 1C). In addition, immunohischemistry results of HNRNPD based on ‘The Human Protein Atlas’ database representing the protein expression was shown in Figure 1D.

3.2 | Pan-cancer genetic alternations of hnRNP genes

The mutation frequency of hnRNP genes were analysed, and the results indicated that most hnRNP genes were frequently mutated in UCEC (Figure 2A). The overall average mutation frequency ranged from 0% to 14.9%, and hnRNP genes including HNRNPM, HNRNPUL1, HNRNPL showed relatively high mutation frequencies. Several cancers such as THCA, PCPG and UVM demonstrated rare hnRNP gene mutations. In order to show more detailed information about hnRNP mutation, we then visualized the mutation details of hnRNP genes in UCEC by on- coplot (Figure 2B). Besides, CCLE database was used to demonstrate the mutation status of hnRNP genes in various human cancer cell lines (Figure 2C). The results indicated that colorectal cancer and lung can- cer cell lines suggested frequent mutations of most hnRNP genes. In addition, the copy number variations of hnRNP genes were also inves- tigated across different cancer types (Figure 2D): HNRNPA2B1 gene showed widespread copy number amplification across various cancer types whereas almost no CNV was detected in LAML.

In order to elucidate the molecular implication of hnRNPs in car- cinogenesis, the relation of hnRNPs with cancer-related pathways was analysed and visualized in Figure 3A. The findings suggested that hnRNP expressions significantly correlated with the acti- vation or suppression of various oncogenic pathways. It could be concluded that hnRNP genes mainly participated in cancer- related pathways including protein secretion, mitotic spindle,

HNRNPCL1
HNRNPAB
HNRNPA1
HNRNPD
HNRNPH1
HNRNPA1L2
HNRNPUL2
HNRNPUL1
HNRNPAO
HNRNPUL2-BSCL2
HNRNPA281
HNRNPL
HNRNPF
HNRNPC
HNRNPU
HNRNPR
HNRNPM
HNRNPDL
HNRNPLL
HNRNPH3
HNRNPH2
HNRNPA1P33
FIGURE 1 Expression profile of hnRNP genes across different cancer types. (A) Expression of hnRNP genes in different cancer and normal samples. The colour in heat map represents the log2 fold change value between cancer and normal. The blue colour represents the low expression in cancer, whereas the red colour represents the high expression in cancer. The * sign represents degree of statistical significance. (B) HNRNPAB expression in 16 types of cancers between cancer and normal tissues. (C) hnRNP protein expression across various cancer types. Each gene expression in one cancer was divided into four groups of high expression, medium expression, low expression and not detected. (D) HNRNPD gene protein expression in 16 cancer types based on immunohischemistry staining results from 'The Human Protein Atlas' database

A

logFC

Adj.P.value * P<0.05 ** P<0.01 *** P <0.001

C

Protein Expression

High

Medium

Low

Not.detected

-2-1 0 1 2

HNRNPUL1

HNRNPL

HNRNPAB

HNRNPR

HNRNPH2

HNRNPM

HNRNPA2B1

HNRNPLL

HNRNPD

HNRNPC

HNRNPU

HNRNPA1

HNRNPF

HNRNPH1

HNRNPDL

HNRNPUL2

HNRNPAO

CHOL

PRAD

BLCA

ESCA

STAD

HNSC

KIRP

KIRC

THCA

COAD

READ

LUSC

LIHC

BRCA

UCEC

LUAD

KICH

glioma

melanoma

BRCA

TECA

COCA

SKCA

URCA

PACA

CECA

ENCA

OV

LUCA

STCA

PRCA

lymphoma

LIHC

RACA

THCA

carcinoid

HNSC

B

D

HNRNPAB

300

300

100

HNRNPAB

300

HNRNPAB

100

HNRNPAB

80

100

30

100

10

30

3

10

10

30

10

cancer

normal

cancer

normal

3

cancer

normal

cancer

normal

BLCA

BRCA

CHOL

COAD

Glioma

Melanoma

Lymphoma

SKCA

HNRNPAB

300

HNRNPAB

300-

100

100

100

HNRNPAB

HNRNPAB

100

30

30

30

30

10

10

10

3

10

cancer

normal

cancer

normal

cancer

normal

cancer

normal

ESCA

HNSC

KICH

KIRC

OV

CECA

BRCA

PRCA

300-

HNRNPAB

HNRNPAB

300 -

100

HNRNPAB

100

HNRNPAB

30

100

300

ER

30

10

10

30

100

3

10

30

3

cancer

normal

cancer

normal

cancer

normal

cancer

normal

KIRP

LIHC

LUAD

LUSC

URCA

RECA

PACA

LIHC

300

HNRNPAB

100

HNRNPAB

300

HNRNPAB

300

HNRNPAB

300

100

100

30

100

30

10

30

10

30

.

10

3

cancer

normal

cancer

normal

cancer

normal

cancer

normal

PRAD

READ

STAD

UCEC

STCA

HNSC

COCA

LUCA

G2/M checkpoint, DNA repair, IL6/JAK/STAT3 signal and co- agulation. At the same time, the numbers of the correlated path- ways of each gene were summarized, of which hnRNP genes of HNRNPF, HNRNPH2, HNRNPU and HNRNPUL1 are more likely to be implicated in oncogenic processes (Figure 3B). As pathways of adipogenesis, androgen response and hypoxia showed differ- ent correlations with diverse hnRNP genes, we summarized the correlations among different hnRNP genes as well as the specific correlation with adipogenesis, androgen response and hypoxia in Figure 3C. We found that hnRNPs might work together in carcinogenesis as significant correlations were detected such as HNRNPL-HNRNPAB (r = 0.83), HNRNPUL2-HNRNPA0 (r = 0.58) and HNRNPAB-HNRNPLL (r = 0.57). At last, the effect of hnRNP genes on immune cell infiltration was shown in Figure 3D. The

most relevant immune cells included T help cells, NK cells, CD8 positive T cells and neutrophils. HNRNPH2, HNRNPU, HNRNPDL and HNRNPA0 all demonstrated significant correlation with im- mune cell infiltration.

3.4 Prognostic significance of hnRNP genes

The prognostic significance of hnRNP genes in different cancer types was analysed by Cox regression (Figure 4A). In cancers including ACC, LIHC and LUAD, most hnRNPs were associated with worse survival of cancer patients. In contrast, hnRNPs predicted better prognosis in cancers such as KIRC and THYM. In addition, certain hnRNP gene might exert obvi- ous different prognostic effect across various cancer types. For instance,

|

FIGURE 2 Pan-cancer genetic alternations of hnRNP genes. (A) Pan-cancer mutation frequency of hnRNP genes. (B) Oncoplot for hnRNP genes in UCEC. HNRNPM showed the most frequent mutation in UCEC. (C) The mutation frequency of hnRNP genes across common cancer cell lines. Each circle from the outside to the inside represents a type of tumour cell line (breast, gastric, colorectal, kidney, lung, bone, ovary, skin, fibroblast and liver). (D) The copy number variations frequency of hnRNP genes in different cancers

A

Mutation Frequency

B

Altered in 137 (25.85%) of 530 samples.

19526

0

0.02 0.04 0

0.06

0

40

HNRNPM

0

HNANPM

14%

HNRNPUL1

HNRNPULT

13%

HNRNPL

HNANPH2

12%

HNRNPU

HNRNPU

12%

HNRNPA2B1

HNRNPR

10%

HNRNPF

HNRNPD

9%

HNRNPR

HNANPL

HNRNPH2

HNANDE

HNRNPA1

HARNPAAR

7%

HNRNPD

HNANPH!

7%

HNRNPUL2

HNANPLE

5%

HNRNPAO

HNANPOL

0%

HNRNPLL

HNRNRAZB1

6%

HNRNPA1L2

HNRNPC

6%

HNRNPDL

HNANPA!

5%

HNRNPH3

HNANPH3

5%

HNRNPCLT

2%

HNRNPH1

MNANPULZ

2%

HNRNPC

HNANPAIL2

HNRNPAB

HNANPAO

HNRNPCL1

HNRNPA1P33

Missense_Mutation

Frame_Shift_Ins

HNRNPUL2-BSCL2

In_Frame_Ins

Translation_Start_Site

UCEC

COAD

STAD

BLCA

CESC

READ

SKCM

DLBC

ESCA

LUAD

LUSC

HNSC

CHOL

UCS

GBM

PAAD

OV

BRCA

SARC

LAML

ACC

LIHC

KIRP

KIRC

KICH

TGCT

THYM

THCA

UVM

Splice_Site

Nonstop_Mutation

LGG

MESO

PRAD

PCPG

Nonsense_Mutation

· Multi_Hit

Frame_Shift_Del

CNV Frequency

C

D

0.5 Loss 0 Gain 0.5

HNRNPL

HNRNPLL

HNRNPM

HNRNPR

Copy number variation across cancer types

HNRNPH3

HNRNPU

HNRNPAO

HNRNPUL1

HNRNPA1

HNRNPH2

HNRNPA1L2

HNRNPA2B1

HNRNPAB

HNRNPUL2

0.2

Mutation Frequence

HNRNPC

HNRNPCL1

HNRNPH1

HNRNPD

HNRNPDL

HNRNPF

HNRNPAO

HNRNPH1

HNRNPH2

HNRNPF

HNRNPH3

0

HNRNPL

HNRNPLL

HNRNPM

HNRNPDL

HNANPA1

HNRNPR

HNRNPU

HNRNPUL1

HINRNPA1L2

HNRNPUL2

HNRNPD

ACC

LUAD

ESCA

BLCA

CESC

BRCA

LIHC

CHOL

KIRC

KICH

GBM

COAD

KIRP

HNSC

UCEC

DLBC

LGG

LAML

HNRNPCL1

HNRNPA2B

HNRNPC

HNRNPAB

HNRNPA1 and HNRNPC showed different prognostic association in di- verse cancer types, which were therefore shown by forest plot to illustrate the specific predictive effect in diverse types of cancers (Figure 4B). As many hnRNP genes demonstrated influence on KIRC prognosis, we per- formed clustering analysis of prognosis-related hnRNP genes (Figure 4℃). The prognosis analysis of the cluster C1 and C2 suggested that C2 cluster was significantly associated with better survival compared with C1 cluster (HR = 0.50, 95% CI = 0.35-0.73, P = . 003), indicating the promising po- tential of hnRNP genes in the prediction of cancer prognosis (Figure 4D).

4 DISCUSSION |

In order to clarify the critical role of alternative splicing regulator heterogeneous nuclear ribonucleoproteins family across various types of cancer, we comprehensively analysed the core genes which belong to hnRNPs family. Based on multiple levels of data from TCGA, genomic and transcriptomic landscape of key hnRNPs fam- ily genes was investigated by pan-cancer analysis. The results sug- gested that hnRNPs were differentially expressed in certain cancers and corresponding controls, which also correlated with prognosis of

patients. The identified correlation between hnRNPs with multiple cancer-related pathways suggested close implication of hnRNPs in the development of various types of cancers.

By comprehensively analysing the transcriptional data of 22 core hnRNP genes in TCGA, we describe the expression landscape of hnRNP genes across different cancer types. Heterogeneous dis- tributions of hnRNP genes were observed in different cancer types: HNRNPA1 and HNRNPAB were highly expressed in most tumours. It has been reported that hnRNPA1 was highly expressed in gastric can- cer tissues, which promote proliferation, migration and EMT of gastric cancer cells.20 In lung cancer, knockdown of HNRNPA1 suppressed the viability and growth as well as induced cell cycle arrest of lung cancer cells.21 The results of previous studies and our analysis all suggested the critical role of HNRNPA1 in the initiation and development of dif- ferent types of cancers. Besides, HNRNPAB overexpression has been found in metastatic cells or cancer tissues in hepatocellular carcinoma patients, which lead to EMT and metastasis of hepatocellular carcinoma cells in vivo.22 The oncogenic effect of HNRNPA1 and HNRNPAB is of great interest to understand the underlying mechanisms of alternative splicing in carcinogenesis, which might provide novel insights into an- ti-tumour therapy. Moreover, HNRNPA1P33 expression was increased

WILEY

FIGURE 3 Association of hnRNPs with cancer-related pathways and immune status. (A) Network diagram demonstrating the correlation between hnRNP genes and cancer-related pathways. Blue node represents the negative correlation pathways, whereas red nodes represent the positive pathways. (B) The number of correlated pathways in each individual hnRNP genes. (C) Correlation between the expression of different hnRNP genes and the correlation between the three tumour-associated pathways and individual hnRNP genes. (D) Correlation between hnRNP genes and immune cells infiltration. The genes in the outer circle represent genes within individual immune cells. Inner circles are formed by hnRNP genes. The size of each gene represents the number of connections

A

B

Nog_HEVE METABOLISM

Nog_HEDGEHOG_SIGNALINGNing_HYPONIA

Nog_ ESTROGIIN RESPONSE LIMATOGENESS

HNANPA ! ANPULA-ESCLA

POR_PS]_PATHWAY POR ADIPOGENESIS

POR BILE ACID_METABOLISM

Positive

Negative

POR NOTCH SIGNALING

Ning PANCREAS BETA CELLS

10

ALLOGRAFT_REJECTION

NONPOL

HNANPAZ51

POR_MTORCI_SIGNRUINHEDGEHOG SIGNALING

Ning KRAS_SIGNALING_ON

Ning_INFA_SIGNALING_VIA_NFKB

NINH2

HINHINPL

POR: KRF_TARGETS

POR_SPERMATOGENESE

Number of Pathway

5

Neg. BILE ACID METABOLISM

Neg. PEROXISOME

HMENPE

HIFINPULZ

Pom MEG TARGETS_V2

POR_XENOBIOTIC_METABOLISM

APICAL JUNCTION

0

ANGIOGENESIS

INENPO

HNANPU

PER MYC_TARGETS_VI

POLANDROGEN RESPONSE

Neg INFLAMMATORY_RESPONSE

5

Ning_CHOLESTEROL HOMEOSTASIS

İNANPULI

HNANPAR

POIK DNIA REPAR

POR GZM-CHECKPOINT

Ning ESTROGEN RESPONSE_BAFLY

Nog_COAGULATION

10

NONPR

INPM

APICAL SURFACE

POR_WANT_BIETA CATENIN_SIGNALING POR HEME_METABOLISM

Nog_IL6_JAK_STATE_SIGNALING

HORNPLL

HNANPAI

OUV RESPONSE ON POR MITOTIC SPINDLE

HNRNPAO

HNRNPA1

HNRNPA1L2

HNRNPA2B1

HNRNPAB

HNRNPC

HNRNPD

HNRNPDL

HNRNPF

HNRNPH1

HNRNPH2

HNRNPH3

HNRNPL

HNRNPLL

HNRNPM

HNRNPR

HNRNPU

HNRNPUL1

HNRNPUL2

HNRNPUL2-BSCL2

Nog_UV_RESPONSE_DN

OR UNFOLDED PROTEIN R

Ng. MYOGENESIS

IHNENPC

Nog_PROTEIN_SECRETION

HNAINPAO

HNFINPHI

AKT_MITOR_SIGNALING

Ning_PI3K_AKT_MTOR_SIGNALING CON NEXTNODOTIC METABOLISM

POR TOF BETA SIGNINGPROTEIN SECRETION

SSONY

1800

CHIT1

COLZA2

CTSK

LaNa MSR1

SCARB2

SCG5

SGMS1

CORNZAIP

D

SLC2SA12

DNASB1

DI ASUS

€ T300

ABTT

CAMLG

HAUS3

KATGA

SEC240

KLF9

LEPROTL 1

MAPKAPKS-AS1

Macrophages

C

HNRNPLL

HNRNPAB

HNANPL

HNRNPA1

HNRNPA1L2 HNRNPD

PPP1R2

HNRNPDL HNRNPU

HNRNPH2

HNRNPH3

HNRNPUL2-BSCL2

HNRNPUL1

HNANPUL2

HNRNPA2B1 HNRNPF

HNRNPCL1

PPPERSO

APA1

HNRNPC

HNANPH1

HNRNPAO

HNRNPM

HNRNPR

NUP107

PHF10

PRRS

r

helper cells

RØM3

CD8

SF1

GOLGABA

LRBA

HNANPD

HNRNPC

HNANPAB

HNRNPLL

cells

SRSF7

HNRŅPDL

TBCC

o

THUMPD1

O

HNRNPAB

HNRNPL

FAMILIA

FRYL

HNANPA2B1

DOXSO

HNANPF

o

TMC6

TMEM259

O

HNRNPA1

BORA

HNANPA1L2

o

4

HNRNPA1L2

BATE

HNANPH1

TSC2203

ADIPOGENESIS

o

N

HNRNPD

VAMP2

ATFE

o

N

HNRNPDL

HNRNPA1

HNRNPU

ASF1

ZFP3612

O

ZNF22

O

ST

HNRNPC

ANP32B

HNRNPH2

-

-

ZNF609

ZNF741

O

HNRNPH2

HNRNPA0

ZNF91

HNRNPUL2-BSCL2

ZNF528

CEACAMB

ANDROGEN_RESPONSE

o

0

HNRNPH3

ZNF205

HNANPH3

HPGDS

HNRNPH1

KIT

.

o

corr

Mast cells

SLC30AL

0

A

HNRNPUL1

PSMD

@LINC01140

O

S

HNRNPAO

PRIX

HNANPL

PPMTH

o

J

HNRNPUL2

MRCZ

HNRNPUL2-BSCL2

o

HNRNPA2B1

MCM3AP

SPTGS1

-

MAPRE3

HNANPLL

ØSCG2

o

HNRNPF

KANKE

cells

HNANPUL2

OSLC24A3

ΗΥΡΟΧΙΑ

o

N

HNRNPM

IGFBPS

HNRNPM

Neutrophils

TALI

TPS82

O

J

HNRNPR

HNANPR

HNANPUL1

HNRNPCL1

HNANPU

o

-

FZR

COCS

BCL

·HPSE

COR3

VWASA

APBBZ

SGCB

Th1

-

-

LAAN3

LAP8

cells

EGFLO

B cells

OUSPS DGKI

ENNA

ECPR2

SLC25A37

SLC2244

cells

CTLA4 @ CSF26

CD72

SLC15A2

ORSL1

MICAL3

OU53W

LOND

ATP9/

APOD

PRKCO

NCALD

VZWILL

CD3D

SCNJA

in COAD, READ and LUAD whereas decreased in CHOL, PRAD and BLCA, which indicated that hnRNPs might exert different functions in diverse kinds of tumours.

Pan-cancer genetic alternations of hnRNP genes indicated that the overall average mutation frequency ranged from 0% to 14.9%, and hnRNP genes including HNRNPM, HNRNPUL1, HNRNPL showed high mutation frequencies. The critical role of HNRNPM in the development and metastasis has been investigated in colon cancer,23 prostate cancer24 and breast cancer.25,26 Importantly, next-generation sequencing has suggested HNRNPL as a key regula- tor of prostate cancer via modulating the alternative splicing of multi- ple RNAs such as the core oncogene androgen receptor.27 It is worth noting that most hnRNP genes were frequently mutated in UCEC, a certain type of cancer with high global mutation burden.28 Several cancers such as THCA, PCPG and UVM demonstrated rare hnRNP gene mutations. Besides, human cancer cell lines analysis based on CCLE demonstrated that colorectal cancer and lung cancer cell lines possess frequent mutations of most hnRNP genes. Future investiga- tions concerning the mutations of hnRNP genes in lung cancer and colorectal cancer might reveal critical evidence of contribution of

hnRNPs in the development of cancer. In addition, the copy number variations investigation revealed that HNRNPA2B1 gene showed widespread copy number amplification across various cancer types whereas almost no CNV was detected in LAML.

The correlation analysis of hnRNPs with cancer-related path- ways suggested that hnRNPs significantly contributed to the ac- tivation or suppression of various oncogenic pathways including protein secretion, mitotic spindle, G2/M checkpoint, DNA repair, IL6/JAK/STAT3 signal and coagulation. Different hnRNPs were found to be associated with distinct cancer pathway alterations, suggesting different functional effects of hnRNPs within the same alternative splicing regulator family. HNRNPA1 was significantly associated with pathways including DNA repair, G2/M checkpoint, E2F targets and myc targets. HNRNPAB showed correlation with G2/M checkpoint and wnt-ß-catenin pathways. In addition, hnRNP genes of HNRNPF, HNRNPH2, HNRNPU and HNRNPUL1 are more likely to be implicated in oncogenic processes. Previously, HNRNPU has been reported to facilitate chromatin looping and p300-mediated transactivation of transcription factor early growth response 1, thus promoting cancer progression.29 Furthermore,

|

2.610.760.970.791.380.820.941.091.031.160.641.821,390,831.561.490.960.750.960.841.442.020,470.991.130.890.711.170.120.951.430.96HNRNPAO
5.320.810.731.071.211.030.740.841.123.670.732.050.840.641.401.410.800.960.931.551.591.330.811.411.021.152.280.540.180.580.790.68HNRNPA1
3.960.920.710.830.971.231.020.830.948.250.910.770.700.901.030.850,990.941.010.650.988.870.691.110.971.180.330.370.611.011.020.83HNRNPA1L2
0.861.100.960,850.551.030,870.871.001.690.911.300.880.731.331.040.990,750,091.781.121.300.050.911.081.220.611.001.910.590.76HNRNPA1P33
8.480.830.981.000.861.051.120.951.249.051.031.131.011.631.491.470.891.530.871.220.703.780.621.460.970.920.430.850.210.801.250.98HNRNPA2B1
3.551.110.970.790.590.761.831.221.193.491.281.722.041.091.001.520.911.570.791.320.653.150.601.041.200.860.740.690.330.801.986.09HNRNPAB
3.710.910.731.130.511.130.970.671.304.030.781.891.381.091.421.850.941.200.962.060.932.080.991.701.110.940.380.280.130.811.001.45HNRNPC
1.310.711.020.851.131.012.820.961.221.390.651.730.741.151.481.090.831.520.911.181.191.041.001.340.891.230.000.860.130.991.531.40HNRNPCL1
3.750.770.820.710.751.020.860.881.163.860.741.571.531.351.451.341.071.020.911.070.518.100,571.251.050.950.701.010.001.040.901.83HNRNPD
5.160.010.910.721.181.031.120.021.041.990.710.060.050.601.261.091.001.271.001.011.540.290.611.071.071.020.450.040.310.691.001.03HNRNPDL
4.310.841.040.810.620.781.350.960.862.160.701.511.081.301.761.550.921.070.881.320.532.350.991.041.080.780.450.760.110.681.111.15HNRNPF
4.900.830.750.900.660.781.351.040.778.771.051.151.041.751.940.990.961.360.970.921.992.590.261.271.020.850.961.640.111.001.301.18HNRNPH1
0.491.051.000.861.091.171.280.731.193.340.611.541.580.751.171.000.900.520.990.930.611.520.971.171.010.940.350.570.480.911.251.70HNRNPH2
7.310.760.950.930.980.970.790.791.043.810.651.231.230.571.621.540.871.520.931.130.562.810.581.680.801.301.390.470.100.820.790.80HNRNPH3
3.620.970.010.780.671.040,430.880.003.860.991.511.751.011.551.540.831.500.001.410.621.330.581.201.250.940.730,470.000.870.721.90HNRNPL
2.760.940.920.960.560.700.620.741.283.950.651.291.271.301.700.960.831.431.001.140.541.660.901.280.851.040.441.060,240.871.402.61HNRNPLL
5.580.900.790.650.520.980.380.850.923.700.001.181.201.421.721.390.901.301.000.820.633.100.511.061.020.900.950.570.210.660.940.85HNRNPM
5.170.980.921.041.160.760.790.871.114.180.711.590.921.571.611.580.940.890.971.310.591.930.801.661.090.960.420.910.220.941.011.21HNRNPR
4.651.010.910.771.120.980.750.811.074.180.551.331.211.451.461.300.861.730.971.281.491.570.611.381.230.980.400.550.201.051.001.00HNRNPU
3.721.000.750.880.470.881.210.931.102.040.781.281.651.421.351.320.871.750.961.180.990.990.761.131.411.060.440.690.451.120.950.73HNRNPUL1
4.521.000.630.991.161.000.880,851.052.110.830.911.870.751.371.300.961.500,891.201.472.481.191.241.041.050.330.400.271.000.732.79HNRNPUL2
2.620.991.211.670.981.181.230.841.043.910.541.041.490.991.061.370.971.081.130.901.712.750.581.150.911.001.010.740.391.021.151.20HNRNPUL2-BSCL2
FIGURE 4 Prognostic significance of hnRNP genes. (A) Summary of the correlation between expression of hnRNP genes and survival of different cancers. Red colour represents high risk of death, whereas blue colour represents low risk of death. (B) Forest plot for the prognostic analysis of HNRNPA1 and HNRNPC across various cancer types. (C) Heat map showing the clustering for KIRC patients based on the expression of hnRNP genes. (D) Survival analysis for cluster group based on hnRNP genes in KIRC

A

High Risk

Low Risk

P >= 0.05

C

Group Event

2

Group

High

Gender

1

Low

Age

HNRNPCL1

Event

0

Alive

HNRNPA2B1

Dead

Gender

HNRNPDL

-1

Male Female

HNRNPH3

-2

Age

90

HNRNPUL2-BSCL2

HNRNPAO

30

ACC BLCA

BRCA

CESC

CHOL

COAD

DLBC

GBM

HNSC

KICH

KIRC

KIRP

LAML

LGG LIHC

LUAD

LUSC

MESO

OV

PAAD

PCPG

PRAD

READ

SARC

SKCM

STAD

TGCT

THCA

THYM

UCEC

UCS

UVM

HNRNPM

B

Hazard Ratio (95% CI)

Hazard Ratio (95% CI)

Cancer Patients

HNRNPF

ACC

79

5.82(2.50-$1.30)

3.71(1.74-7.89)

HNRNPH2

BLCA 411

0.81(0.60- 1.08)

0.91(0.68-1.21)

BRCA 1104

0.73(0.53- 1.00)

0.73(0.53- 1.00)

HNRNPR

CESC 306

1.07(0.68- 1.70)

1.13(0.71- 1.80)

CHOL

HNRNPU

36

+1.21(0.48-3.06)

0.51(0.20- 1.28)

COAD

471

1.03(0.69- 1.53)

1.13(0.76- 1.68)

DLBC

48

0.74(0.20-2.72)

0.97(0.24-3.86)

Strata + C1

+ C2

GBM

168

0.84(0.60- 1.17)

0.67(0.48-0.94)

HNSC

502

1.12(0.86- 1.46)

1.30(0.99- 1.69)

D

KICH

65

3.67(0.99-13.55)

+4.03(1.09-14.93)

1.00

KIRC

535

0.73(0.54- 0.99)

0.78(0.58- 1.06)

KIRP

289

2.05(1.13- 3.71)

1.89(1.05-3.41)

LAML

151

0.84(0.54- 1.30)

1.38(0.89-2.14)

Survival probability

0.75

LGG

529

0.64(0.46- 0.90)

1.09(0.77-1.52)

LIHC

374

1.40(0.99- 1.98)

1.42(1.01-2.01)

LUAD 526

1.41(1.06- 1.89)

1.85(1.39-2.47)

LUSC 501

0.80(0.61- 1.05)

0.94(0.72- 1.23)

0.50

MESO

86

0.96(0.61- 1.53)

1.20(0.75- 1.90)

OV

379

0.93(0.72- 1.20)

0.96(0.74-1.24)

PAAD

178

1.56(1.03- 2.35)

2.06(1.36-3.12)

0.25

P = 0.003

PCPG

183

1.59(0.40-6.36)

0.93(0.23-3.72)

PRAD 499

1.33(0.38-4.60)

2.08(0.60-7.22)

Hazard Ratio = 0.5

READ

167

0.81(0.38- 1.74)

0.99(0.46-2.10)

95% CI: 0.35 - 0.73

SARC

263

1.41(0.95-2.09)

1.70(1.14-2.52)

SKCM

471

1.02(0.78- 1.33)

1.11(0.85- 1.45)

0.00

STAD

375

1.15(0.83- 1.59)

0.94(0.68-1.30)

0

1000

2000

3000

4000

TGCT

156

2.28(0.31-16.46)

0.38(0.05-2.73)

Time

THCA

510

0.54(0.20- 1.44)

0.28(0.10-0.74)

THYM

119

0.18(0.05-0.68)

0.13(0.03-0.47)

Number at risk

UCEC

548

0.58(0.38- 0.87)

0.81(0.54- 1.22)

Strata

UCS

56

0.79(0.40- 1.55)

1.00(0.51- 1.95)

C1

426

243

90

27

3

UVM

80

0.68(0.30- 1.55)

1.45(0.64-3.31)

C2

107

65

32

13

0

0

1000

2000

3000

4000

0

0.5

1

1.5

2

0

0.5

1

1.5

2

Time

HNRNPA1

HNRNPC

we also found that hnRNPs might work together in carcinogen- esis as significant correlations were detected such as HNRNPL- HNRNPAB, HNRNPUL2-HNRNPA0 and HNRNPAB-HNRNPLL. As for immune cell infiltrations, the most relevant immune cells of hnRNPs included T help cells, NK cells, CD8 positive T cells and neutrophils. Genes of HNRNPH2, HNRNPU, HNRNPDL and HNRNPA0 all demonstrated significant correlation with immune cell infiltration. HNRNPU has been found to interact with NF-KB- responsive Long Non-coding RNA FIRRE to modulate the mRNAs of certain inflammatory genes in innate immune system.3º The close relation between alternative splicing regulator hnRNPs and immune system might offer new idea for future studies on immune therapy against cancer.

Pan-cancer prognostic analysis of hnRNP genes suggested that most hnRNPs were associated with worse survival of can- cer patients in cancers including ACC, LIHC and LUAD. However, hnRNPs predicted better prognosis in cancers such as KIRC and THYM. In addition, HNRNPA1 predicted worse prognosis of can- cers including ACC, KIRP, LUAD and PAAD but was associated with better survival in cancers of KIRC, LGG, THYM and UCEC. These results suggested that HNRNPA1 might exert obviously dif- ferent prognostic effect across various cancer types. Previously, high HNRNPUL2 expression has been reported to predict poor survival of multiple cancers. 31 Significant association of HNRNPH expression and prognosis of colorectal cancer patients has been suggested by tissue microarray.32 Oral squamous cell carcinoma

patients with increased HNRNPD expression significantly cor- related with shorter recurrence-free survival.33 These findings indicated that hnRNPs were closely implicated in the prognosis of various cancers. As many hnRNP genes demonstrated influence on KIRC prognosis, we further performed clustering analysis of prognosis-related hnRNP genes. The prognosis analysis of the cluster C1 and C2 suggested that C2 cluster was significantly as- sociated with better survival compared with C1 cluster, indicating that hnRNP genes might be used as a prognostic predictor of can- cer in the future.

5 CONCLUSION

In summary, our study systematically demonstrated the expres- sion, mutation, copy number variation, functional pathways and prognostic value of alternative splicing regulator hnRNPs across a series of cancers. The expressions of hnRNPs suggested signifi- cant association with oncogenic pathways including protein se- cretion, mitotic spindle, G2/M checkpoint, DNA repair, IL6/JAK/ STAT3 signal and showed correlation with immune regulations of T help cells, NK cells, CD8 positive T cells and neutrophils. The evaluation of hnRNPs distributions could predict prognosis of can- cer patients. These findings provide novel evidence for the inves- tigation of hnRNPs in the development and therapy of cancer in the future.

CONFLICT OF INTEREST

All of the authors declare that there is no conflict of interest.

AUTHOR CONTRIBUTION

Hao Li: Formal analysis (equal); Writing-original draft (equal). Jingwei Liu: Formal analysis (equal); Writing-original draft (equal). Shixuan Shen: Investigation (lead); Methodology (lead). Di Dai: Validation (equal); Visualization (equal). Shitong Cheng: Data curation (equal); Investigation (equal). Xiaolong Dong: Formal analysis (supporting); Visualization (supporting). Liping Sun: Investigation (equal); Writing- review & editing (equal). Xiaolin Guo: Project administration (equal); Writing-review & editing (equal).

DATA AVAILABILITY STATEMENT

All of the data in this article were used the TCGA datasets (https:// www.cancer.gov/about-nci/organization/ccg/research/structural -genomics/tcga).

ORCID

İD

Xiaolin Guo https://orcid.org/0000-0001-8197-690X

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SUPPORTING INFORMATION

Additional supporting information may be found online in the Supporting Information section.

How to cite this article: Li H, Liu J, Shen S, et al. Pan-cancer analysis of alternative splicing regulator heterogeneous nuclear ribonucleoproteins (hnRNPs) family and their prognostic potential. J Cell Mol Med. 2020;24:11111-11119. https://doi. org/10.1111/jcmm.15558