Oncogenic mechanisms of HOXB13 missense mutations in prostate carcinogenesis

Abstract

The recurrent germline mutation HOXB13 p.(Gly84Glu) (G84E) has recently been identified as a risk factor for prostate cancer. In a recent study, we have performed full sequencing of the HOXB13 gene in 462 Portuguese prostate cancer patients with early-onset and/or familial/hereditary disease, and identified two novel missense mutations, p.(Ala128Asp) (A128D) and p.(Phe240Leu) (F240L), that were predicted to be damaging to protein function. In the present work we aimed to investigate the potential oncogenic role of these mutations, comparing to that of the recurrent G84E mutation and wild-type HOXB13. We induced site-directed mutagenesis in a HOXB13 expression vector and established in vitro cell models of prostate carcinogenesis with stable overexpression of either the wild-type or the mutated HOXB13 variants. By performing in vitro assays we observed that, while the wild-type promotes proliferation, also observed with the F240L variant along with a decrease in apoptosis, the A128D mutation decreases apoptosis and promotes anchorage independent growth. No phenotypic impact was observed for the G84E mutation in the cell line model used. Our data show that specific HOXB13 mutations are involved in the acquisition of different cancer-associated capabilities and further support an oncogenic role for HOXB13 in prostate carcinogenesis.

The Homeobox gene, HOXB13, Regulates a Mitotic Protein-Kinase Interaction Network in Metastatic Prostate Cancers

“…HOXB13 is expressed in androgen-dependent LNCaP and VCaP cell lines as well as androgen-independent mCRPC cell lines, C4-2B and 22Rv1 27 . We chose C4-2B for further evaluation as this cell line expresses HOXB13 and AR, shows significant resistance to the anti-androgen Enzalutamide, and metastasizes in castrated immunocompromised male mice 2,16 .…”

“…To confirm that the HOTPAM9 genes are regulated in a HOXB13-dependent manner PC cell lines 27 C4-2B, LNCaP, VCaP and PC3 were transfected with control or HOXB13 silencing RNAs either singly or pooled (siRNAs). After 48 hours, the relative expression of HOTPAM9, HOXB13 and c-MYC was examined by quantitative Reverse Transcriptase PCR (qRT-PCR) with gene-specific primers.…”

Impact of the G84E variant on HOXB13 gene and protein expression in formalin-fixed, paraffin-embedded prostate tumours

“…However, in an in vitro cell model study using site directed mutatgenesis, Cardoso and colleagues (2016) found that the G84E variant had no phenotypic impact, i.e. there was no change in proliferation or apoptosis compared to the wild-type cell model 23 . In our study of FFPE prostate tumour tissue, we found no difference in HOXB13 protein expression between G84E carriers and non-carriers; a finding supported by a larger IHC study of radical prostatectomy samples from 101 G84E carriers and 99 non-carriers 24 .…”

Contributions of HOX genes to cancer hallmarks: Enrichment pathway analysis and review

“…In addition to those genes, HOXA13 and HOXB13 are also known to be associated with evasion of apoptosis. 58–62 HOXB9 expression has been reported as significantly increased in tumor tissues and to be associated with a poor prognosis, chemotherapy resistance, invasion, and metastasis. 63–65 Vychytilova-Faltejskova et al 66 showed in their recent study that HOXB9 downregulation in p53-proficient colorectal cell lines led to significant increases in the number of apoptotic cells and decreased proliferation and migration rates (Figure 2).…”

“…59,60 Conversely, HOXB13 is a known activator of apoptotic pathways, and HOXb13 loss-of-function mutations are highly associated with an increased risk of prostate cancer related to increased levels of cell proliferation and decreased rates of apoptosis. 61,62,73,85,86 Collectively, the HOX genes that are involved in cell death responses can act as oncogenes or as tumor suppressor genes. Their functional relationship to this cancer hallmark will depend on the specific role the HOX gene had in maintaining cellular homeostasis in normal tissues.…”