3224

HOXC8

homeobox C8;HOXC8;homeobox C8

Hox-3.1, mouse, homolog of|homeo box 3A|homeo box C8|homeobox protein Hox-3A|homeobox protein Hox-C8

12q13.3

protein-coding

expression profiling has identified metastasis-associated microRNAs (miRNA) but technical limitations hinder the discovery of metastasis-suppressing miRNAs. In this study, we sought metastasis-suppressing miRNAs by functional screening. Individual miRNAs were lentivirally introduced into metastatic MDA-MB-231 breast cancer cells and analyzed for effects on cell migration, a critical step in cancer metastasis. Among 486 miRNAs screened, 14 were identified that included all of the members of the miRNA-196 family (miR-196a1, miR-196a2, and miR-196b). Enforced expression of miR-196a1/2 or miR-196b abrogated in vitro invasion and in vivo spontaneous metastasis of breast cancer cells, indicating that members of the miR-196 family are potent metastasis suppressors. We found that miR-196 inhibited the expression of transcription factor HOXC8. Functional linkage was implied by small interfering RNA-mediated knockdown of HOXC8, which suppressed cell migration and metastasis, and by ectopic expression of HOXC8, which prevented the effects of miR-196 on cell migration and metastasis. Unlike other metastasis-associated miRNAs that have been described, the expressions of miR-196 were not correlated with breast cancer cell migration or the metastatic status of clinical breast tumor specimens. Instead, we detected an excellent correlation between the ratio of miR-196 to HOXC8 messages and the migratory behavior of breast cancer cell lines as well as the metastatic status of clinical samples. Our findings identify miRNA-196s as potent metastasis suppressors and reveal that the ratio of miR-196s to HOXC8 mRNA might be an indicator of the metastatic capability of breast tumors.

BACKGROUND: The transcription factor HOXC8 regulates many genes involved in tumour progression. This study was to investigate the role of HOXC8 in pancreatic ductal adenocarcinoma (PDAC) growth and metastasis. METHODS: The Hoxc8 expression was determined in 15 PDAC cell lines and human specimens by RT-polymerase chain reaction and/or immunohistochemistry. The effects of HOXC8 silencing by RNA interference were investigated by functional tests. RESULTS: The Hoxc8 mRNA expression in PDAC cell lines was negatively related to their growth in vivo. Except for Suit2-007 cells, only those with low Hoxc8 mRNA expression grew in nude rats. Successful down-regulation of HOXC8 expression caused increased proliferation, migration (P tumour stage (P=0.09). In primary and metastatic tumour samples, immunohistochemical staining for HOXC8 was stronger in surrounding than in neoplastic tissues. Furthermore, grading of primary carcinomas was negatively associated with HOXC8 staining (P=0.03). Liver metastases showed the lowest HOXC8 expression of all neoplastic lesions. CONCLUSION: These data indicate that HOXC8 expression is inversely related to PDAC progression and metastasis.

BACKGROUND: Homeobox (HOX)-containing proteins have been identified as regulators controlling the coordinated expression of genes involved in development and differentiation. Recent data also suggest a possible involvement of HOX genes in malignant transformation and/or progression. We have previously shown that HOXC8 expression was selectively turned on in human cervix cancer cells compared with normal keratinocytes, suggesting that HOXC8 may be involved in the process leading to the transformation of cervix keratinocytes [Alami et al.: Biochem Biophys Res Commun 257:738-745, 1999]. METHODS: RT-PCR and in situ hybridization experiments were performed to investigate the expression and cell type localization of HOXC8 transcripts in human prostate cancer cell lines and tissues. In situ hybridization was performed with the use of an HOXC8 anti-sense digoxigenin-labeled probe to investigate HOXC8 mRNA expression in 27 prostate cancer tissue specimens. RESULTS: Out of the three human prostate cancer cell lines tested, DU-145 and PC3 but not LNCaP cells expressed detectable amount of HOXC8 transcripts. Results from in situ hybridization experiments demonstrated that HOXC8 gene was expressed mainly in malignant epithelial cells. Furthermore, the staining intensity in epithelial cells was significantly increased in high Gleason score carcinomas (scores 7-9, n = 12; labeling intensity 2 + to 3 +) compared with the one observed in low and intermediate Gleason score tumors (scores 3-6, n = 15; labeling intensity 0 and 1 +) (ANOVA test, P < 0.0001). CONCLUSIONS: Our data showing that HOXC8 overexpression is associated with the loss of tumor differentiation in human prostate cancer suggests that HOXC8 may play a role in the acquisition of the invasive and metastatic phenotype of this malignancy.