Cancer arises from cellular biological anomalies, where genomic mutations disrupt normal growth regulation, leading to uncontrolled cell proliferation [42]. Aberrantly proliferating cells deplete nutrients and invade surrounding tissues, significantly impairing quality of life and posing a life-threatening risk. The 2022 global cancer statistics estimate 20 million new cases and 9.7 million cancer-related deaths worldwide [43]. Cancer is a major global public health problem. Therefore, it is necessary to understand the biological characteristics and physiological processes of tumors.
hnRNPs, as RBPs, exhibit functional diversity and complexity, playing a vital role in cellular nucleic acid metabolism [44]. Among them, hnRNPAB is a key member, though data on hnRNPA3 and hnRNPA0 remain sparse. In contrast, hnRNPA1 and hnRNPA2/B1 are notably expressed and actively involved in mRNA translation [46] and splicing [47], which has led to a research emphasis on these proteins. Recent studies indicate that hnRNPAB is expressed in gastric, colorectal, breast, and liver cancers, contributing significantly to tumorigenesis and progression [48–50].
The TIMER and GEPIA databases were employed to assess hnRNPAB expression across various cancer and normal tissues. Analysis of BRCA, CESC, CHOL, GBM, and STAD indicated significantly elevated hnRNPAB levels in cancerous tissues compared to normal counterparts. This overexpression in multiple cancer types was corroborated by the CPTAC proteomics dataset and the BioGPS database. Notably, in normal cells, hnRNPAB is predominantly expressed at high levels in immune cells, particularly CD56 + NK cell lines. CD56 + NK cells, essential for immune surveillance and response, swiftly target infected or transformed cells [51]. This observation implies that hnRNPAB may influence immune cell activation, differentiation, and cytotoxicity, highlighting its role in immune regulation.
To assess the clinical significance of hnRNPAB expression in cancer patients, survival and Cox regression analyses were performed using the TCGA dataset. The findings indicated that elevated hnRNPAB expression is significantly associated with poor survival outcomes in tumors such as KICH, KIRC, KIRP, LAML, LIHC, LUAD, and UVM. This correlation suggests that hnRNPAB expression could serve as a prognostic marker in cancer. Notably, hnRNPAB expression impacts the prognosis of various renal cancers. Existing evidence has shown that abnormal expression of HNRNP family proteins can lead to renal damage through multiple pathways. For instance, the loss of HNRNPF in renal tubules decreases SGLT2 expression, reducing hyperfiltration and renal injury [52], while HNRNPC targets the miR-182-5p/CYP1B1 axis to regulate KIRC metastasis [53]. Nevertheless, research on hnRNPAB's role in renal injury and cancer remains sparse, highlighting the need for further investigation.
Genetic variation of hnRNPAB in various cancers was investigated, with a focus on mutation status in the TCGA cohort. Amplification emerged as the predominant mutation, with rates of 7.24% in KIRC and 4.4% in ACC, occurring at different stages of cancer progression. Validation through the CBioPortal dataset established a significant positive correlation between hnRNPAB expression and copy number. Furthermore, analysis of the correlation between hnRNPAB mutation rates and clinical outcomes indicated that higher mutation rates in ACC, KIRC, LGG, LUAD, PRAD, and SKCM were associated with poorer overall survival, suggesting a strong link between hnRNPAB mutations and unfavorable prognosis.
DNA methylation epigenetic characteristics are recognized as valuable cancer biomarkers [54]. Analysis via the UALCAN database indicated a general reduction in hnRNPAB gene methylation in various tumor tissues compared to normal tissues. Investigation of hnRNPAB methylation patterns across different cancers identified specific CpG sites, such as "cg06538757," associated with poor patient prognosis. Additionally, analysis using the MEXPRESS database confirmed a significant correlation between hnRNPAB methylation levels and copy number variation in various cancer samples. Phosphorylation, with its intricate and diverse effects, significantly influences cancer progression. Abnormal proliferation, invasion, and metastasis of cancer cells often correlate with dysregulation in multiple signaling pathways, including protein phosphorylation modifications [55]. Analysis of the CPTAC dataset revealed variable phosphorylation levels of hnRNPAB across different cancers compared to normal tissues, with significant alterations at the S255 gene locus in most tumor samples. This study establishes a foundation for further investigation into the mechanisms of hnRNPAB methylation and phosphorylation in tumorigenesis and progression, providing valuable insights for its potential as a therapeutic target or biomarker.
GSVA analysis predicted signaling pathways associated with hnRNPAB across various tumor types. Up-regulated genes were significantly enriched in cell cycle-related pathways, indicating hnRNPAB's role in promoting tumorigenesis and progression via cell cycle regulation. Additionally, up-regulated genes were enriched in signaling pathways such as MTORC1, a key regulator of cell growth and metabolism that activates various metabolic processes [56]. This suggests hnRNPAB supports tumor cell proliferation by modulating the MTORC1 pathway and its downstream effects. Moreover, down-regulated genes were significantly enriched in metabolism-related pathways, suggesting hnRNPAB's involvement in metabolic reprogramming.
Mounting evidence highlights the significant role of the TME in tumor onset and progression [57]. Recent advancements in cancer research and treatment have shifted focus from a tumor-centric model to one centered on the TME [58]. Analysis of hnRNPAB expression in relation to pan-cancer immune cell infiltration revealed a negative correlation with the infiltration of CD8 + T cells, CD4 + T cells, and NK cells in most cancers. Tumors with mutant hnRNPAB exhibited significantly higher levels of immune infiltration compared to those with wild-type hnRNPAB. This indicates that hnRNPAB may enhance the TME by suppressing the infiltration of these critical immune cells, and mutations in hnRNPAB could influence tumor behavior by altering the immune microenvironment. hnRNPAB exhibited a significant positive correlation with CAF infiltration levels in KIRP, LIHC, THCA, and UVM. CAFs promote primary tumor initiation and progression by modulating tumor cell proliferation, survival, migration, invasion, and treatment resistance through cytokine secretion [59]. Analysis using the TIMER2.0 database indicated that in liver cancer, hnRNPAB expression positively correlated with CAF markers such as CAV1, CD101, COL1A1, COL1A2, FAP, TGF-β3, and VIM. In KIRP, hnRNPAB expression also showed positive correlations with VIM, CD101, COL1A1, TGF-β2, TGF-β3, EPCAM, and CAV1.
In summary, this study examines the biological and clinical significance of hnRNPAB across various cancers, demonstrating that high hnRNPAB expression is associated with poor prognosis in cancers such as those of the kidney and liver. Additionally, hnRNPAB appears to promote tumor growth and metastasis by modulating immune cell infiltration and CAF activity within the TME. The investigation also covers hnRNPAB gene mutation and methylation status, and their association with tumor metabolic reprogramming and immune evasion. These results provide a foundational basis for further research on hnRNPAB as a potential therapeutic target or biomarker.