Original Article |
Corresponding author: Vijayashree Priyadharsini Jayaseelan ( viji26priya@gmail.com ) © 2024 Amba Esakki, Anitha Pandi, Smiline A S Girija, Vijayashree Priyadharsini Jayaseelan.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Esakki A, Pandi A, Girija SAS, Jayaseelan VP (2024) Correlating the genetic alterations and expression profile of the TRA2B gene in HNSCC and LUSC. Folia Medica 66(5): 673-681. https://doi.org/10.3897/folmed.66.e117367
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Introduction: Transformer (TRA2B) is a serine/arginine-rich (SR)-like protein family that regulates the alternative splicing of several genes in a concentration-dependent manner. Amplification of the TRA2B gene, which codes for TRA2B, occurs in several malignancies, including those of the lung, cervix, head and neck, ovary, stomach, and uterine.
Materials and methods: The present study design follows a computational approach to predict the molecular mechanisms underlying TRA2B alterations in two cancer phenotypes, viz., lung and head and neck squamous cell carcinoma. The genetic alteration in the TRA2B gene was identified using the cBioportal database. The gene expression pattern in both the cancer types and their survival pattern concerning the expression profile was demonstrated using UALCAN. The microRNA targets of the TRA2B gene were identified using the miRDB database.
Results: Genetic alteration was found to be 27% and 48% in HNSCC and LUSC datasets, respectively. The alterations included gene amplification, missense, nonsense, and splice site mutations. The gene expression profile of TRA2B correlated well with the gene amplification demonstrated by patients in both groups. However, the upregulation of TRA2B did not correlate well with the survival profile in LUSC patients. The downregulation of TRA2B markedly affected the survival of HNSCC patients, which can be attributed to the functions of microRNAs targeting TRA2B transcripts.
Conclusion: Although TRA2B was found to be a potential diagnostic marker exhibiting a differential expression pattern for HNSCC, the employability of this gene as a prognostic marker needs more experimentation. Also, the influence of microRNAs on dysregulated gene expression should be considered to gain a better understanding of the underlying molecular mechanisms precipitating the disease.
cancer, genetics, gene alterations, gene expression, microRNA
Head and neck squamous cell carcinomas (HNSCCs) originate from the mucosal epithelium in the oral cavity, pharynx, and larynx.[
The alterations in the DNA sequence can dramatically affect the functions of the protein encoded by the gene. Gross chromosomal abnormalities such as deletions, translocations, inversions, and insertions have been linked to numerous syndromes, developmental disorders, metabolic, infectious diseases, and cancer.[
Recent research has unraveled numerous epigenetic mechanisms that are directly or indirectly associated with cancer. In this context, miRNAs have been explored to a more considerable extent and were found to play a significant role in controlling cell division, apoptosis, and growth in several physiological and pathologic processes.[
In line with these facts, the present study has been designed to dissect the role of the TRA2B gene, transformer-2 protein homolog beta (TRA2B), a member of the serine/arginine-rich protein family, in 2 closely similar cancer types viz., HNSCC and LUSC. Many diseases, including cancers, are linked to the dysregulation of TRA2B. It is expected to find TRA2B over-expression in various cancers, such as lung, prostate, and ovarian cancers. Through its modulation of cancer cell growth and invasion, TRA2B contributes to the malignant progression of cancers. TRA2B has been found to have pro-oncogenic splicing targets, namely CD44, HipK3, and Nasp-T.[
This study analyzed the sample datasets for HNSCC (head and neck squamous cell carcinoma) and LUSC (lung squamous cell carcinoma). The dataset consisted of 528 HNSCC patients acquired from TCGA (The Cancer Genome Atlas) Firehose legacy. The majority of patients were found to be smokers and alcohol consumers. The LUSC dataset consists of 511 samples from LUSC patients, among which 178 had information about the copy number variations and mutations. The mutation count was much higher in HNSCC. The disease’s onset age was higher in LUSC than in HNSCC. The complete demographic details of the patients are given in Tables
Demographic details of the HNSCC dataset (TCGA, Firehose Legacy) used for analysis
Gender | Male (n = 386) Female (n = 142) |
Mutation count | 6-3181 |
Diagnosis age | 19-90 years |
Smoking status | Smokers: 515 Data not available: 12 Unknown: 1 |
Alcohol history | Yes: 352 No: 165 Data not available: 11 |
Neoplasm histologic grade | Grade 1: 63 Grade 2: 311 Grade 3: 125 Grade 4: 7 Grade GX: 18 Data not available: 4 |
Race category | White: 452 African: 48 Asian: 11 American Indian or Alaska native: 2 Data not available: 15 |
Demographic details of LUSC dataset (TCGA, Firehose Legacy) used for analysis
Gender | Male: 373 Female: 131 Unknown: 7 |
Age | <50 - 85 years |
Race | White: 351 Black or African: 31 Asian: 9 Not available: 120 |
Mutation count | <25 - >475 |
Cancer type | Non-small cell lung carcinoma |
Smoking Status | Category 1: 18 Category 2: 134 Category 3: 83 Category 4: 252 Not available: 19 |
The cBioportal database (http:// cbioportal.org) is a platform that contains clinical and molecular data from various cancer types submitted by different groups. This portal can be used to analyze genetic alterations such as mutations, copy number variations, and survival for the expression. By selecting an appropriate dataset, one can query for genetic modifications of a specific gene or a list of genes. In addition, a detailed description of the mutations in candidate genes was obtained via a lollipop plot. This mutation plot provided information on the frequency of mutations and their type, the domain in which they occur, and their consequence.[
Various computational tools, such as SIFT, PolyPhen, and PROVEAN, were used to analyze the consequences of mutations identified in the TRA2B gene. SIFT (Sorting Intolerant from Tolerant) differentiates between sequences or elements that exhibit various tolerance levels or intolerance to mutations or genetic variations (https://sift.bii.a-star.edu.sg/). A score below 0.05 indicates a state where the mutations/variants are predicted to be potentially damaging or intolerant.[
The UALCAN web portal helps to analyze and interpret cancer omics data, including transcriptomics, proteomics, and patient survival information. The portal uses data acquired from the Cancer Genome Atlas (TCGA) as the primary dataset for analysis. It allows users to visualize the expression profile of protein-coding genes, non-coding genes, and epigenetic factors such as methylation. You can access the portal through this website: http://ualcan.path.uab.edu.[
MicroRNAs are a type of RNA that do not code for proteins but instead regulate the process of gene expression. They bind to specific mRNA targets and break them down, leading to the downregulation of the targeted genes. Predicting which miRNAs target differentially expressed genes is crucial for understanding the role of epigenetic factors in carcinogenesis. To identify microRNAs that target genes identified from the hub, researchers use the miRDB database, which can be found at http://mirdb.org.[
The latest version of the STRING tool, version 10.5, gathers, evaluates, and combines all publicly accessible sources of protein-protein interaction data and analyzes them utilizing computational tools. The evidence of association present in the STRING database is classified into gene neighborhoods, gene fusions, gene co-occurrence, co-expression, experiments, databases, and text mining. You can find more information about this tool at https://string-db.org/.[
The oncoprint data for the TRA2B gene in the HNSCC dataset demonstrated gene amplification in 20% of the patients; the other 1% gene alteration comprised of X286_splice (splice-site mutation), M1? (nonstart mutation), R45H, R277L and R111P (missense mutation) (Fig.
The SIFT, PolyPhen, and PROVEAN predictions demonstrated that two out of five mutations, R111P (arginine to proline) and R277L (arginine to leucine), had a deleterious effect on the proteins. The other mutations were benign and tolerated with neutral impact, except for the R219L (arginine to leucine) mutation, which was predicted to be deleterious with PROVEAN alone (Table
SIFT, PolyPhen, and PROVEAN predictions for the missense mutations identified in the TRA2B gene in both datasets
Mutations | SIFT | PolyPhen | PROVEAN |
R45H | Tolerated | Benign | Neutral |
R111P | Affect protein function | Probably damaging* | Deleterious |
A145S | Tolerated | Benign | Neutral |
R219L | Tolerated | Benign | Deleterious |
R277L | Affect protein function | Possibly damaging@ | Deleterious |
Gene amplification or duplication events generally increase RNA transcripts. The gene expression among the normal, HNSCC, and LUSC primary tumor groups showed a significant change in the transcript levels (p-value <10-12) (Fig.
Box Whisker plot demonstrating the gene expression profile of TRA2B gene (a) HNSCC and (b) LUSC datasets. The gene expression between the normal and the HNSCC primary tumor group showed a significant change in the transcript levels (p-value <10-12). The gene expression profile was statistically significant between the normal and LUSC primary tumors (p-value <10-12). A p-value less than 0.05 is considered significant.
Kaplan Meier plot demonstrating survival probability of patients exhibiting high and low levels of TRA2B. A statistically significant change in survival was observed with TRA2B expression (p=0.0098) in HNSCC. There was no statistically significant association between the gene expression levels and survival of LUSC patients (p=0.5). A p-value less than 0.05 is considered significant.
The HNSCC patients with increased expression of TRA2B survive longer when compared to patients with low/medium expression. The epigenetic components, such as miRNAs, can markedly affect the gene expression levels. While investigating the non-coding RNAs targeting TRA2B, we could identify 181 microRNAs. Since analyzing all the microRNA targets is out of the scope of this study, the top 10 targets were chosen for further expression and survival analysis. There were four microRNAs viz., hsa-miR-570, hsa-miR-3619, hsa-miR-214, and hsa-miR-335, which were found to be upregulated (Table
Target score | miRNA name | Gene expression in HNSCC (p-value) | Expression pattern | Survival (p-value) | Gene expression in LUSC (p-value) | Expression pattern | Survival (p-value) | |
98 | hsa-miR-570 | 2.177×10-5 | Upregulation | 0.79 | 1.624×10-12 | Upregulation | 0.86 | |
97 | hsa-miR-587 | NA | NA | NA | NA | NA | NA | |
96 | hsa-miR-3619 | <10-12 | Upregulation | 0.27 | 1.624×10-12 | Upregulation | 0.2 | |
95 | hsa-miR-214 | 4.722×10-3 | Upregulation | 0.55 | 7.055×10-12 | Upregulation | 0.49 | |
95 | hsa-miR-761 | NA | NA | NA | NA | NA | NA | |
94 | hsa-miR-1468 | 1.977×10-8 | Downregulation | 0.67 | 1.174×10-2 | Downregulation | 0.87 | |
93 | hsa-miR-335 | 2.626×10-4 | Upregulation | 0.32 | 1.409×10-6 | Upregulation | 0.8 | |
93 | hsa-miR-1-1 | 2.001×10-3 | Downregulation | 0.1 | NA | NA | NA | |
93 | hsa-miR-206 | 2.035×10-3 | Downregulation | 0.1 | 2.418×10-2 | Downregulation | 0.087 | |
92 | hsa-miR-613 | NA | NA | NA | NA | NA | NA |
The protein-protein interaction network of TRA2B revealed the following proteins to interact with SRSF1, SRSF2, SRSF3, SRSF6, SRSF7, SRSF9, SRSF10, RBMX, HNRNPC, and HNRNPH1. Most proteins belong to mRNA processing machinery; hence, TRA2B can be considered a key protein that can regulate the gene expression of several candidate genes (Fig.
Alternative RNA splicing is an essential process that regulates gene expression in cells. It plays a crucial role in creating different versions of the same gene, known as transcript isoforms, produced at different times in specific cells. Defects in alternative splicing are common in human tumors, and RNA splicing regulators have recently been identified as a new class of oncoproteins or tumor suppressors.[
A similar study reported the over-expression of TRA2B in the endometrial carcinoma cells, as assessed by RT-qPCR and Western bot technique. The dysregulation of this gene inevitably conferred viability and proliferative advantage to the cells. The treatment of such EC cells with siRNA-TRAB2 dramatically affected the proliferative ability of the cells. The inhibition of invasiveness and acceleration of apoptosis was also observed.[
The present study is the first of its kind to identify the correlation between alterations observed in the TRA2B gene with the impact of these alterations on gene expression and survival of HNSCC and LUSC patients. The observations clearly showed that despite the high expression of TRA2B in HNSCC patients, the prognosis was reasonable compared to the low/medium expression group. The observations presented here contradict the findings reported by researchers in various other cancer types. The presentation thus requires further experimentation to gain more insight into the role of TRA2B as a tumor suppressor rather than an oncogenic protein in HNSCC cases. In addition, the role of non-coding RNA, miRs, was also elucidated in consonance with the same expression profile in both datasets. The downregulation of TRA2B could be affected by microRNAs that target this gene. In this regard, four miRNAs were identified as differentially upregulated in the HNSCC tumor. Although these miRNAs did not return any significant correlation with the survival of patients, they can be considered potential candidates for studying gene expression and regulation of the TRA2B gene.
The results accumulated through the present study gave a clear understanding of the convergent pathways associated with two closely related cancer phenotypes viz., HNSCC and LUSC. The epigenetic targets and gene expression patterns were similar in both cancer types. The employability of the TRA2B gene to HNSCC as a diagnostic or a prognostic marker has to be further investigated using experimental procedures to gain concrete evidence on the role of this gene in establishing HNSCC.
The authors hereby declare that there is no conflict of interest in this study.
The authors are grateful to all the consorts and groups involved in compiling patient data for public use. Our sincere thanks also go to all the patients who have indirectly contributed to the scientific community by providing consent for sharing their data for research use.