Obesity and a western diet have been linked to high levels of bile acids and the development of colon cancer. Specifically, increased levels of the bile acid deoxycholic acid (DCA), an established tumor promoter, has been shown to correlate with increased development of colorectal adenomas and progression to carcinoma. Herein we investigate the mechanism by which DCA leads to EGFR-MAPK activation, a candidate mechanism by which DCA may promote colorectal tumorigenesis. DCA treated colon cancer cells exhibited strong and prolonged activation of ERK1/2 when compared to EGF treatment alone. We also showed that DCA treatment prevents EGFR degradation as opposed to the canonical EGFR recycling observed with EGF treatment. Moreover, the combination of DCA and EGF treatment displayed synergistic activity, suggesting DCA activates MAPK signaling in a non-canonical manner. Further evaluation showed that DCA treatment increased intracellular calcium levels and CAMKII phosphorylation, and that blocking calcium with BAPTA-AM abrogated MAPK activation induced by DCA, but not by EGF. Finally we showed that DCA-induced CAMKII leads to MAPK activation through the recruitment of c-Src. Taken together, we demonstrated that DCA regulates MAPK activation through calcium signaling, an alternative mechanism not previously recognized in human colon cancer cells. Importantly, this mechanism allows for EGFR to escape degradation and thus achieve a constitutively active state, which may explain its tumor promoting effects.

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The concentration of estrogen receptor protein in breast-tumor tissue is generally expressed in units of femtomoles of estradiol bound by the receptor per milligram of cytosol protein. The sensitivity of the estrogen receptor radioligand assay is therefore related to the specific activity of the steroid label used for the binding assay, the amount of the receptor protein in the volume of cytosol used, and the protein concentration in the cytosol. In this paper, we discuss factors affecting the sensitivity of the estrogen receptor assay and present various approaches for optimizing the assay. We also describe a procedure that involves a radioiodinated estradiol of high specific activity, a micro-technique for preparing tumor cytosol, and a micro-assay procedure with which the estrogen receptor protein can be measured in as little as 50 mg (wet weight) of tissue.

Bile acids deoxycholic acid (DCA) and ursodeoxycholic acid (UDCA) have contrasting effects on tumor development. DCA is measurable at increased levels in the serum of colorectal adenocarcinoma patients and is associated with disease progression. DCA is also a well-established tumor promoter. On the other hand, UDCA is a chemopreventative agent revealed to suppress the recurrence of highly dysplastic polyps in a phase III clinical trial. Remarkably, retrospective investigation of the data had shown that UDCA's efficacy as a chemopreventive mediator was gender specific. UDCA significantly lowered the recurrence of advanced lesions in males, but caused a significant increase in the recurrence of advanced lesions in females. Our lab is in pursuit of understanding the gender specific chemopreventive role of UDCA. Estrogen receptor β (ERβ) has been shown to play a significant role in controlling the development of colorectal cancer. Therefore, we hypothesized that the altered regulation of the ERβ pathway by UDCA might explain the gender specificity of this molecule. In order to assess this, we analyzed the effects of UDCA on ERβ to those of the known tumor promoter DCA in both male and female human adenocarcinoma cell lines. Female HT-29 colorectal adenocarcinoma cells induced the phosphorylation of ERβ, as well as up-regulated gene expression of estrogen response elements (EREs), showing stimulated activity of this hormonal receptor. Moreover, we found that pre-treating the cells with PD98059, a MEK 1/2 inhibitor, UDCA and DCA-induced phosphorylation of ERβ, along with increased ERE gene expression, was significantly reduced. Collectively, this data suggests that UDCA and DCA can stimulate ERβ signaling through the non-genomic MAPK signaling cascade; suggesting that UDCA's gender-specific effects may be due, in part, to signaling through hormone receptors. Citation Format: Jesse Trujillo. Bile acids modulate estrogen receptor β signaling through nongenomic actions in colorectal cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4599.

In previous studies, Ursodeoxycholic Acid (UDCA) was investigated as a chemopreventive drug for the prevention of colorectal adenoma recurrence. These studies revealed that the efficacy of UDCA was gender-specific. The use of UDCA in men significantly lowered the odds of advanced lesions in men, but significantly increased the odds of advanced lesions in women, more specifically, in females who were younger, obese, or whose diet was high in fat. The gender specific role of UDCA led us to investigate this bile acids’, along with deoxycholic acid's (DCA), ability to activate the estrogen receptor in colon cancer. Estrogen receptor β (ERβ) is the predominant estrogen receptor in both normal and malignant human colon tissue, and loss of ERβ has been shown to be critical for tumor cell differentiation. Elevated concentrations of bile acids have previously been shown to promote colon cancer and growing evidence indicates that these molecules play a vital role in regulating cell signaling and gene expression. In our current studies, through western blot and qRT-PCR analysis, we have shown that DCA-treated HT-29 colorectal adenocarcinoma cells significantly induce the phosphorylation of ERβ, as well as increase gene expression of the pS2 estrogen response element (ERE). UDCA was also shown to induce phosphorylation of ERβ, but much later than DCA. However, UDCA increases gene expression of pS2 at much earlier time points than DCA. In addition, we have also shown that when pre-treating HT-29 cells with the MEK 1/2 inhibitor, PD98059, bile acid-induced phosphorylation of ERβ is significantly reduced, along with ERE gene up-regulation. Collectively, this data suggests that bile acids are inducing the activation of ERβ through a ligand-independent mechanism via the MAPK signaling cascade. Citation Format: Jesse Trujillo. Elucidating the mechanism of bile acid-induced activation of estrogen receptor β in colorectal adenocarcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5006. doi:10.1158/1538-7445.AM2015-5006