Browsing by Subject "ABCG2"

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    Lansoprazole and its Metabolites in the Treatment of TNBC and the Contribution of ABCG2 to CC-115 Resistance
    (2019-08) Beebe, Jennifer Diane; Zhang, Jian-Ting; Jerde, Travis; Safa, Ahmad; Xie, Jingwu; Fishel, Melissa
    Triple-negative breast cancer (TNBC) is a highly aggressive form of breast cancer with a dismal prognosis. Targeted therapies for breast cancer with expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) are currently available; however, due to the lack of ER, PR, and HER2 in TNBC, targeted therapies are limited. While surgery and traditional chemotherapy remain the standard of care, development of a new treatment strategy for TNBC is needed to improve clinical outcomes. Fatty acid synthase (FASN) has been implicated as a metabolic oncogene and has given cancer cells a survival advantage by increasing NHEJ repair. Recently, it has been shown that FDA-approved proton pump inhibitors, used for the treatment of acid related digestive diseases, have antitumor effects. Here, I show that a metabolite of lansoprazole, 5-hydroxy lansoprazole sulfide, has increased potency over parent compound lansoprazole. 5-hydroxy lansoprazole sulfide inhibits FASN, leading to a decrease in PARP and NHEJ DNA repair activity in TNBC. Ultimately, this leads to an increase in DNA damage and cell death via apoptosis. These findings suggest that 5-hydroxy lansoprazole sulfide, as a metabolite of lansoprazole, may have better activity in suppressing TNBC cells and that 5-hydroxy lansoprazole sulfide may be developed as a therapeutic for TNBC treatment. Furthermore, due to the role of FASN in increasing NHEJ repair, we hypothesized that FASN played a role in resistance to CC-115, a dual mTOR/DNA-PK inhibitor currently in clinical trials, by increasing DNA-PK activity. However, it was found that ABCG2, an ATP-binding cassette transporter, and not FASN, has a role in CC-115 resistance. ABCG2 effluxes CC-115 from cancer cells, increasing resistance to treatment. Inhibition of ABCG2 by FTC or PZ39C8 led to accumulation of CC-115 within cells and sensitization to treatment. Therefore, ABCG2 status should be assessed to stratify patients into treatment groups, increasing the efficacy of CC-115 treatment.
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    The role of GLI2-ABCG2 signaling axis for 5Fu resistance in gastric cancer
    (Elsevier, 2017-08-20) Yu, Beiqin; Gu, Dongsheng; Zhang, Xiaoli; Liu, Bingya; Xie, Jingwu; Pediatrics, School of Medicine
    Gastric cancer is a leading cause of cancer-related mortality worldwide, and options to treat gastric cancer are limited. Fluorouracil (5Fu)-based chemotherapy is frequently used as a neoadjuvant or an adjuvant agent for gastric cancer therapy. Most patients with advanced gastric cancer eventually succumb to the disease despite the fact that some patients respond initially to chemotherapy. Thus, identifying molecular mechanisms responsible for chemotherapy resistance will help design novel strategies to treat gastric cancer. In this study, we discovered that residual cancer cells following 5Fu treatment have elevated expression of hedgehog (Hg) target genes GLI1 and GLI2, suggestive of Hh signaling activation. Hh signaling, a pathway essential for embryonic development, is an important regulator for putative cancer stem cells/residual cancer cells. We found that high GLI1/GLI2 expression is associated with some features of putative cancer stem cells, such as increased side population. We demonstrated that GLI2 knockdown sensitized gastric cancer cells to 5Fu treatment, decreased ABCG2 expression, and reduced side population. Elevated GLI2 expression is also associated with an increase in tumor sphere size, another marker for putative cancer stem cells. We believe that GLI2 regulates putative cancer stem cells through direct regulation of ABCG2. ABCG2 can rescue the GLI2 shRNA effects in 5Fu response, tumor sphere formation and side population changes, suggesting that ABCG2 is an important mediator for GLI2-associated 5Fu resistance. The relevance of our studies to gastric cancer patient care is reflected by our discovery that high GLI1/GLI2/ABCG2 expression is associated with a high incidence of cancer relapse in two cohorts of gastric cancer patients who underwent chemotherapy (containing 5Fu). Taken together, we have identified a molecular mechanism by which gastric cancer cells gain 5Fu resistance.