Browsing by Author "Roa, Juan C."
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Item Evaluation of the chemopreventive potentials of ezetimibeand aspirin in a novel mouse model of gallbladderpreneoplasia(2020) Rosa, Lorena; Lobos-González, Lorena; Munoz Durango, Natalia; Garcıa, Patricia; Bizama, Carolina; Gomez, Natalia; Gonzalez, Ximena; Wichmann, Ignacio A.; Saavedra, Nicolas; Guevara, Francisca; Villegas, Jaime; Arrese, Marco; Ferreccio, Catterina; Alexis M. Kalergis, Alexis M.; Miquel, Juan Francisco; Espinoza, Jaime A.; Roa, Juan C.Gallbladder stones (cholecystolithiasis) are the main risk factor for gallbladder cancer (GBC), a lethal biliary malignancy with poor survival rates worldwide. Gallbladder stones are thought to damage the gallbladder epithelium and trigger chronic inflammation. Preneoplastic lesions that arise in such an inflammatory microenvironment can eventually develop into invasive carcinoma, through mechanisms that are not fully understood. Here, we developed a novel gallbladder preneoplasia mouse model through the administration of two lithogenic diets (a low- or a high-cholesterol diet) in wild-type C57BL/6 mice over a period of 9 months. Additionally, we evaluated the chemopreventive potentials of the anti-inflammatory drug aspirin and the cholesterol absorption inhibitor ezetimibe. Both lithogenic diets induced early formation of gallbladder stones, together with extensive inflammatory changes and widespread induction of metaplasia, an epithelial adaptation to tissue injury. Dysplastic lesions were presented only in mice fed with high-cholesterol diet (62.5%) in late stages (9th month), and no invasive carcinoma was observed at any stage. The cholesterol absorption inhibitor ezetimibe inhibited gallbladder stone formation and completely prevented the onset of metaplasia and dysplasia in both lithogenic diets, whereas aspirin partially reduced metaplasia development only in the low-cholesterol diet setting. This model recapitulates several of the structural and inflammatory findings observed in human cholecystolithiasic gallbladders, making it relevant for the study of gallbladder carcinogenesis. In addition, our results suggest that the use of cholesterol absorption inhibitors and anti-inflammatory drugs can be evaluated as chemopreventive strategies to reduce the burden of GBC among high-risk populations.Item Small molecule inhibitor screening identifified HSP90 inhibitor 17-AAG as potential therapeutic agent for gallbladder cancer(Impact Journals, 2017) Weber, Helga; Valbuena, Jose R.; Barbhuiya, Mustafa A; Stein, Stefan; Kunkel, Hana; Garcia, Patricia; Bizama, Carolina; Riquelme, Ismael; Espinoza, Jaime; Kurtz, Stephen; Tyner, Jeffrey; Calderón, Juan Francisco; Corvalan, Alejandro; Grez, Manuel; Pandey, Akhilesh; Leal-Rojas, Pamela; Roa, Juan C.Gallbladder cancer (GBC) is a lethal cancer with poor prognosis associated with high invasiveness and poor response to chemotherapy and radiotherapy. New therapeutic approaches are urgently needed in order to improve survival and response rates of GBC patients. We screened 130 small molecule inhibitors on a panel of seven GBC cell lines and identified the HSP90 inhibitor 17-AAG as one of the most potent inhibitory drugs across the different lines. We tested the antitumor efficacy of 17-AAG and geldanamycin (GA) in vitro and in a subcutaneous preclinical tumor model NOD-SCID mice. We also evaluated the expression of HSP90 by immunohistochemistry in human GBC tumors.In vitro assays showed that 17-AAG and GA significantly reduced the expression of HSP90 target proteins, including EGFR, AKT, phospho-AKT, Cyclin B1, phospho-ERK and Cyclin D1. These molecular changes were consistent with reduced cell viability and cell migration and promotion of G2/M cell cycle arrest and apoptosis observed in our in vitro studies.In vivo, 17-AAG showed efficacy in reducing subcutaneous tumors size, exhibiting a 69.6% reduction in tumor size in the treatment group compared to control mice (p < 0.05).The HSP90 immunohistochemical staining was seen in 182/209 cases of GBC (87%) and it was strongly expressed in 70 cases (33%), moderately in 58 cases (28%), and weakly in 54 cases (26%).Our pre-clinical observations strongly suggest that the inhibition of HSP90 function by HSP90 inhibitors is a promising therapeutic strategy for gallbladder cancer that may benefit from new HSP90 inhibitors currently in development.