In this study, we analyzed the significance of anoikis, a biological process closely related to metastasis, in the development of bladder cancer. At the same time, we analyzed the genes related to anoikis (ETV7, CASP6, SCD, NGF, LAMC1) based on the TCGA database. We also found SCD can promote the progression of Bca. Then, we constructed a risk score based on lasso regression analysis. This model was used to analyze the immune cell infiltration and drug sensitivity of patients. Further, we constructed a nomogram to evaluate the prognosis of bladder cancer based on the clinicopathological data of patients.
Anoikis is a key mechanism for organisms to prevent exfoliated cells from re-adhering to new substrates in the wrong location[13, 14]. However, in the tumor microenvironment, tumor cells will form a unique survival phenotype, which enables them to do the exfoliation of ECM[15]. Without initiating the programmed death mechanism of anoikis, it will be more conducive to cell migration to other organs or lymphoid tissues and will aggregate to form metastases, eventually leading to lymphatic metastasis, hematogenous metastasis, and further metastasis[16, 17]. When anoikis tolerance occurs, the expression of fibronectin, collagen IV, and other proteins is significantly decreased, while the expression of laminin and metalloproteinases 9 is significantly increased [18, 19]. Therefore, maintaining the integrity of cell anoikis function will be an important means to prevent tumor metastasis in future treatments. In our study, we also found a series of changes in mRNA levels that are closely related to anoikis. Changes in these genes may regulate anoikis tolerance in bladder cancer cells. Interestingly, among these genes, we found that LAMC1 can be translated to produce laminin. Our results also show that LAMC1 expression is increased in bladder cancer and is associated with poor prognosis, which may all be related to LAMC1-induced anoikis tolerance.
In our study, we found that bladder cancer cell loss is closely related to SCD, a key molecule in the cellular process of ROS [20]. Metabolic differences between normal and cancer cells, the mitochondrial TCA cycle, and the shift from oxidative phosphorylation to glycolysis play an important role in tumor progression. Lu et al. report that cells disengaged from ECM induces anoikis tolerance by reducing glucose oxidation and increasing their antioxidant capacity [21].
In the past five years, immunotherapy has played a significant role in advanced or progressive bladder cancer. The landscape changes of the immune microenvironment of bladder cancer can also effectively reflect the efficacy of immunotherapy. Anoikis tolerance is a change in the microenvironment of bladder cancer, making tumor cells easier to colonize and metastasize [22]. Tsai et al. also reported that IL-17A can enhance anoikis resistance in breast cancer, regulate the immune landscape of the tumor microenvironment, and promote cancer metastasis [23]. Tang et al. found that mesenchymal stem cells secrete IL-8, which enhances the resistance of osteosarcoma cells to anoikis and lung metastasis through the CXCR1/Akt axis[24]. In our study, we found that anoikis-related gene scores are also closely related to immunity. On the one hand, the higher the Riskscore score, the lower the regulatory T cells (Treg), which may benefit patients from immunotherapy[25, 26]. Treg is a subset of cells with significant immunosuppressive effects. On the other hand, the higher the Riskscore, the lower the proportion of CD8+ T cells and the higher the proportion of M2 macrophages, which is often a manifestation of insensitivity to immunotherapy[27, 28]. Of course, the interpretation of this result may require a more detailed subset analysis of CD8+ T cells and macrophages.
There are still some limitations that need to be pointed out in this study. This study was based on the TCGA database for excavation studies, missing external validation cohorts, and multi-center validation. These issues need to be resolved in future studies, and we must also evaluate whether this model is applicable to the Chinese population. Another issue of concern is that the molecular mechanism of anoikis tolerance regulating the development of bladder cancer needs further research. In subsequent experiments, we will continue to conduct in vivo experimental verification.