Decreased expression of transcription factor Homeobox A11 and its potential target genes in bladder cancer

Bladder cancer (BC) ranks as the ninth most commonly diagnosed cancer worldwide. The presence of a transcription factor (TF) has been uncovered as a significant contributor to the pathophysiological changes of cancers. In present study, we elucidated the expression and clinical significance of Homeobox A11 (HOXA11) in BC for the first time, and originally investigated HOXA11 as a TF. Employing in-house immunohistochemistry (IHC), we incorporated 137 BC and 34 non-BC cases to detect the expression of HOXA11 protein in BC tissues. HOXA11-related RNA-sequencing (RNA-seq) expression and RNA microarrays were collected from public databases, the "sva" and "limma" R packages were implemented to integrate and normalize the RNA-seq data and microarrays separately. Integration expression was carried out to further evaluate the HOXA11 expression by utilizing the standard mean difference (SMD). The expression level of HOXA11 in various BC cell lines was also evaluated. We further systematically analyzed the downstream target genes of HOXA11 in BC by utilizing Chromatin Immunoprecipitation Sequencing (ChIP-seq) profiles, differentially expressed genes (DEGs), and HOXA11-related genes. Modification of histone marks on the promoter region of target genes were also discovered by histone ChIP-seq data. Results of the IHC and RNA-seq revealed the protein and mRNA expression of HOXA11 was significantly decreased in BC tissues compared to non-BC tissues (2.98 ± 1.48 vs. 8.23 ± 2.64; 6.87 ± 1.54 vs. 8.38 ± 1.42). Five platforms significantly revealed the down-regulation of HOXA11 expression in BC (GPL96, GPL570, GPL6102, GPL6884, and GPL13497). A similar decreased trend was discovered in BC tissues in expression integration with the incorporated SMD reaching -0.843 (-1.362 ~ -0.325, p = 0.001) and -1.051 (-1.674 ~ -0.428, p = 0.001). Expression of HOXA11 was down-regulated in most of the BC cell lines. COL1A1 was considered as a final HOXA11 target gene and positively related to HOXA11 with the correlation coefficient as 0.584 (95% CI: 0.371-0.739, p < 0.001). HOXA11 regulates COL1A1 expression in BC via H3K27ac modification. The expression of COL1A1 was down-regulated with the SMD reached -0.312 (p < 0.001). In conclusion, HOXA11 expression is markedly decreased and might promote the transcription of COL1A1 to inhibit BC.