Reciprocal regulation of BMF and BIRC5 (Survivin) linked to Eomes overexpression in colorectal cancer.

Eomesodermin (Eomes) is a T-box transcription factor that has been implicated in the etiology of colorectal cancer and other human malignancies. We screened a panel of human primary colon cancers and patient-matched controls (n = 30) and detected Eomes overexpression at the mRNA and protein level. Similar results were obtained in a panel of rat colon tumors and adjacent normal-looking colonic mucosa (n = 24). In human colon cancer cells, forced overexpression of Eomes enhanced cell viability and protected against staurosporine-induced apoptosis. On the other hand, knocking down Eomes resulted in reduced cell viability, G2/M cell cycle arrest, and apoptosis induction. The apoptotic mechanism centered on the reciprocal downregulation of anti-apoptotic BIRC5 (Survivin) and upregulation of proapoptotic Bcl-2 modifying factor (BMF). In patients with colorectal cancer, high EOMES expression (n = 95) was associated with poor overall survival compared with individuals exhibiting low EOMES levels (n = 80). We conclude from the current investigation, and prior literature, that Eomes has a divergent role in cancer development, with evidence for tumor suppressor and oncogenic functions, depending on stage and tissue context. Further studies are warranted on the apoptotic mechanisms linked to the reciprocal regulation of BMF and BIRC5 in human colorectal cancers characterized by Eomes overexpression.

Nrf2 status affects tumor growth, HDAC3 gene promoter associations, and the response to sulforaphane in the colon.

BACKGROUND: The dietary agent sulforaphane (SFN) has been reported to induce nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2)-dependent pathways as well as inhibiting histone deacetylase (HDAC) activity. The current investigation sought to examine the relationships between Nrf2 status and HDAC expression in preclinical and translational studies. RESULTS: Wild type (WT) and Nrf2-deficient (Nrf2(-/+)) mice were treated with the colon carcinogen 1,2-dimethylhydrazine (DMH) followed by 400 ppm SFN in the diet (n = 35 mice/group). WT mice were more susceptible than Nrf2(-/+) mice to tumor induction in the colon. Tumors from WT mice had higher HDAC levels globally and locally on genes such as cyclin-dependant kinase inhibitor 2a (Cdkn2a/p16) that were dysregulated during tumor development. The average tumor burden was reduced by SFN from 62.7 to 26.0 mm(3) in WT mice and from 14.6 to 11.7 mm(3) in Nrf2(-/+) mice. The decreased antitumor activity of SFN in Nrf2(-/+) mice coincided with attenuated Cdkn2a promoter interactions involving HDAC3. HDAC3 knockdown in human colon cancer cells recapitulated the effects of SFN on p16 induction. Human subjects given a broccoli sprout extract supplement (200 µmol SFN equivalents), or reporting more than five cruciferous vegetable servings per week, had increased p16 expression that was inversely associated with HDAC3 in circulating peripheral blood mononuclear cells (PBMCs) and in biopsies obtained during screening colonoscopy. CONCLUSIONS: Nrf2 expression varies widely in both normal human colon and human colon cancers and likely contributes to the overall rate of tumor growth in the large intestine. It remains to be determined whether this influences global HDAC protein expression levels, as well as local HDAC interactions on genes dysregulated during human colon tumor development. If corroborated in future studies, Nrf2 status might serve as a biomarker of HDAC inhibitor efficacy in clinical trials using single agent or combination modalities to slow, halt, or regress the progression to later stages of solid tumors and hematological malignancies.