Homeodomain-containing protein HOXB9 regulates expression of growth and angiogenic factors, facilitates tumor growth in vitro and is overexpressed in breast cancer tissue

Overexpressed homeobox B9 regulates oncogenic activities by transforming growth factor-β1 in gliomas

Glioma is the leading cause of deaths related to tumors in the central nervous system. The mechanisms of gliomagenesis remain elusive to date. Homeobox B9 (HOXB9) has a crucial function in the regulation of gene expression and cell survival, but its functions in glioma formation and development have yet to be elucidated. This study showed that HOXB9 expression in glioma tissues was significantly higher than that in nontumor tissues. Higher HOXB9 expression was also significantly associated with advanced clinical stage in glioma patients. HOXB9 overexpression stimulated the proliferation, migration, and sphere formation of glioma cells, whereas HOXB9 knockdown elicited an opposite effect. HOXB9 overexpression also increased the tumorigenicity of glioma cells in vivo. Moreover, the activation of transforming growth factor-β1 contributed to HOXB9-induced oncogenic activities. HOXB9 could be used as a predictable biomarker to be detected in different pathological and histological subtypes in glioma for diagnosis or prognosis.

Homeobox B9 is overexpressed in hepatocellular carcinomas and promotes tumor cell proliferation both in vitro and in vivo

HomeoboxB9 (HOXB9), a nontransforming transcription factor that is overexpressed in multiple tumor types, alters tumor cell fate and promotes tumor progression. However, the role of HOXB9 in hepatocellular carcinoma (HCC) development has not been well studied. In this paper, we found that HOXB9 is overexpressed in human HCC samples. We investigated HOXB9 expression and its prognostic value for HCC. HCC surgical tissue samples were taken from 89 HCC patients. HOXB9 overexpression was observed in 65.2% of the cases, and the survival analysis showed that the HOXB9 overexpression group had significantly shorter overall survival time than the HOXB9 downexpression group. The ectopic expression of HOXB9 stimulated the proliferation of HCC cells; whereas the knockdown of HOXB9 produced an opposite effect. HOXB9 also modulated the tumorigenicity of HCC cells in vivo. Moreover, we found that the activation of TGF-β1 contributes to HOXB9-induced proliferation activities. The results provide the first evidence that HOXB9 is a critical regulator of tumor growth factor in HCC.

Antisense transcript long noncoding RNA (lncRNA) HOTAIR is transcriptionally induced by estradiol

HOTAIR (HOX antisense intergenic RNA) is a long noncoding RNA (lncRNA) that is transcribed from the antisense strand of homeobox C gene locus in chromosome 12. HOTAIR coordinates with chromatin-modifying enzymes and regulates gene silencing. It is overexpressed in various carcinomas including breast cancer. Herein, we demonstrated that HOTAIR is crucial for cell growth and viability and its knockdown induced apoptosis in breast cancer cells. We also demonstrated that HOTAIR is transcriptionally induced by estradiol (E2). Its promoter contains multiple functional estrogen response elements (EREs). Estrogen receptors (ERs) along with various ER coregulators such as histone methylases MLL1 (mixed lineage leukemia 1) and MLL3 and CREB-binding protein/p300 bind to the promoter of HOTAIR in an E2-dependent manner. Level of histone H3 lysine-4 trimethylation, histone acetylation, and RNA polymerase II recruitment is enriched at the HOTAIR promoter in the presence of E2. Knockdown of ERs and MLLs downregulated the E2-induced HOTAIR expression. Thus, similar to protein-coding gene transcription, E2-induced transcription of antisense transcript HOTAIR is coordinated via ERs and ER coregulators, and this mechanism of HOTAIR overexpression potentially contributes towards breast cancer progression.

Antisense oligonucleotide mediated knockdown of HOXC13 affects cell growth and induces apoptosis in tumor cells and over expression of HOXC13 induces 3D-colony formation

HOXC13 is a homeobox containing gene that plays crucial roles in hair development and origin of replication. Herein, we investigated the biochemical functions of HOXC13 and explored its potential roles in tumor cell viability. We have designed a phosphorothioate based antisense-oligonucleotide that specifically knockdown HOXC13 in cultured cells. Cell viability and cytotoxicity assays demonstrated that HOXC13 is essential for cell growth and viability. Antisense-mediated knockdown of HOXC13 affected the cell viability and induced apoptosis in cultured tumor cells. HOXC13 regulates the expression of cyclins and antisense-mediated knockdown of HOXC13 resulted in cell cycle arrest and apoptosis in colon cancer cells. Finally over expression of HOXC13 resulted in 3D-colony formation in soft-agar assay indicating its potential roles in cell proliferation and tumorigenesis.