In this study, we comprehensively explored the in vitro and in vivo roles of CNIH2 in prostate cancer and its clinical significance; to our knowledge, this is the first systematic investigation of CNIH2 in prostate cancer. Prior to this research, the role of CNIH2 in prostate cancer and cancer in general remained largely unexplored. No prior studies have evaluated the functions of CNIH2 in the context of prostate cancer, both in vitro and in vivo, and none have evaluated its clinical relevance within patient cohorts. We demonstrated that high expression of CNIH2 was associated with poorer PFS using TCGA data and clinical cohorts of prostate cancer patients. Additionally, our study confirmed through cellular experiments that the downregulation of CNIH2 expression suppressed the proliferation, migration, and invasion of prostate cancer cells. Further confirmation of these findings was achieved through xenograft tumor experiments in nude mice, which demonstrated that knockdown of this gene significantly inhibited prostate cancer growth in vivo.
The protein encoded by the CNIH2 gene is a constituent of AMPA-type glutamate receptors, which play crucial roles in neurotransmitter signaling within the nervous system23. In the context of cancer, these receptors have been implicated in the development of astrocytoma, glioblastoma, breast carcinoma, lung carcinoma, colon adenocarcinoma, and prostate carcinoma18–22.
The activation of AMPARs is considered a procancer signal. It has been reported that, when activated by glutamate, AMPARs promote the invasion and migration of pancreatic cancer cells through the Kras-MAPK signaling pathway 24. Moreover, AMPARs are expressed in six different small-cell lung cancer cell lines, and the inhibition of AMPARs, either in vivo or in vitro, results in suppressed cell proliferation and reduced MAPK phosphorylation 25. In glioblastoma, AMPARs expressed in glioblastoma cells promote tumor cell proliferation and migration via beta1 integrin-dependent adhesion to the extracellular matrix 26. Previous research has also identified cardiac glycosides as potential candidates for prostate cancer therapy, as these compounds exert anticancer effects. Interestingly, cardiac glycosides, including CNIH2, were found to downregulate the expression of 46 genes, suggesting an oncogenic role for this gene 27. This study indirectly supports the reliability of our research findings. Therefore, one possible mechanism by which CNIH2 contributes to the adverse prognosis of prostate cancer is through its overexpression, which leads to an increase in the quantity or activity of AMPA receptors, thereby enhancing the activation of the AMPA receptor signaling pathway, ultimately resulting in excessive cell proliferation and migration and promoting cancer development and progression.
The androgen receptor axis plays a pivotal role in the pathogenesis and progression of prostate cancer28. D-aspartate not only increases testosterone synthesis by acting on the hypothalamus-pituitary-testis axis but also by directly acting on Leydig cells29–32. Studies have also shown the involvement of AMPARs in this process33. Therefore, another potential mechanism by which CNIH2 expression leads to the progression of prostate cancer could be through an increase in AMPAR expression in testicular cells, subsequently leading to increased testosterone synthesis.
While our study unveiled the clinical significance of CNIH2 expression in prostate cancer for the first time, there are certain limitations to be acknowledged. First, despite validation at the gene expression level and in cellular experiments, a more in-depth investigation and elucidation of the detailed functional mechanisms of CNIH2 and its role in prostate cancer are warranted. Second, while a nude mouse xenograft model was used, it has inherent limitations and cannot fully replicate the complex biological environment of humans. Utilizing different types of animal models may enhance the reliability of the results. Future studies could further strengthen our understanding of the role of the CNIH2 gene in prostate cancer, expand the sample size, improve validation methods, and ultimately increase the credibility and clinical applicability of the research through prospective studies.
This study provides initial insights into the potential role and clinical significance of CNIH2 in prostate cancer. High expression of CNIH2 is associated with poorer prognosis, making it a potential biomarker for prognostic assessment in prostate cancer patients. Both in vitro and in vivo experiments confirmed that CNIH2 knockdown can inhibit the proliferation, migration, and invasion of prostate cancer cells, further supporting its potential role in cancer development. Additionally, the association between CNIH2 and AMPAR suggests potential signaling pathways that may influence the progression of prostate cancer. This research offers new insights for personalized treatment, with the potential to improve the therapeutic outcomes of prostate cancer patients. Despite some limitations, these preliminary findings provide a foundation for future in-depth research and clinical applications, bringing new hope to the management of prostate cancer patients.