Epigenetic inactivation of the candidate tumor suppressor gene HOXB13 in human renal cell carcinoma

Abstract

Epigenetic alterations like DNA methylation and the resulting inactivation of cancer-related genes often contribute to the development of various cancers. To identify the genes that are silenced by aberrant methylation in renal cell carcinoma (RCC), we subjected two RCC lines to methylated CpG island amplification/representational difference analysis. This identified 27 CpG islands. Combined bisulfite restriction analysis of these CpG islands in primary RCC cases revealed that four were methylated in a tumor-specific manner. One of these was identified as the human homeo-box gene B13 (HOXB13) gene, but the remaining three CpG islands were not associated with known genes. The methylation frequencies of HOXB13 in primary RCC samples and lines were 30 and 73%, respectively. The methylation status of HOXB13 correlated with the loss of its expression both in RCC lines and primary tumors, and methyltransferase inhibitor treatment induced the recovery of its expression. Exogenous expression of HOXB13 in RCC cells that lacked endogenous HOXB13 expression suppressed colony formation and induced apoptotic features. Furthermore, HOXB13 methylation correlated positively with tumor grade and microvessel invasion. These results suggest that HOXB13 is a novel candidate tumor suppressor gene in RCC and that its inactivation may play an important role in both RCC tumorigenesis and progression.

HOXB13 promotes ovarian cancer progression

“…Thus far, studies pertaining to the growth modulatory role of HOXB13 in human tumors have been limited to prostate and renal cell carcinoma cell lines. Interestingly, the results of these studies, in contrast to our findings, suggest that HOXB13 plays a tumor suppressor role in the kidney and prostate (14,18,19). These contradictory findings are not necessarily surprising, because it is well known that the activity of HOX proteins depends on the cell in which the protein is acting (20).…”

“…A significant difference between ovary and organs such as prostate and kidney is that HOXB13 is absent in the normal ovary, whereas it is expressed at high levels in the normal prostate and kidney (14,18,19,21), where it is thought to play a role in epithelial cell differentiation (21,22). The HOXB13 expression pattern is reversed in cancers derived from these organs; HOXB13 is up-regulated in ovarian cancers (12) and down-regulated in renal and prostate carcinoma cell lines (14,18,19). Thus, it is likely that tissue-and cell-specific contextual elements, such as endocrine target organspecific coactivators and corepressors, may play a vital role in dictating HOXB13 function.…”

Exploring the two-gene ratio in breast cancer—independent roles for HOXB13 and IL17BR in prediction of clinical outcome

“…The implication of the HOXB13 gene product in different types of cancer is beginning to be elucidated. It has been proposed as a marker for prostate cancer [18], and is also believed to be involved in endometrial cancer [19], cervical cancer [20], as well as renal cell carcinoma [21], and colorectal cancer [22]. In human cutaneous malignant melanoma with distant metastasis, the expression level of certain HOX genes, including HOXB13, was higher than in those melanoma patients without metastases [23], and in endometrial cancer cells, antisense-transfection of the HOXB13 gene reduced the invasive ability of the cells [19].…”

Homeobox gene methylation in lung cancer studied by genome-wide analysis with a microarray-based methylated CpG island recovery assay

“…Several homeobox genes are methylated in tumors of various histological origins. For example, methylation of HOXB13 occurs in 30% of renal cell carcinomas (27), and methylation of genes in the HOXA and HOXD clusters was reported in lung cancer (28). The HOXA5 promoter region was methylated in 16 of 20 p53-negative breast tumor specimens (29).…”