ku-55933 and Colorectal-Neoplasms

Therapeutic resistance is a frequent problem of cancer treatment and a leading cause of mortality in patients with metastatic colorectal cancer (CRC). Recent insight into the mechanisms that confer multidrug resistance has elucidated that the ATP-binding cassette (ABC) superfamily G member 2 (ABCG2) assists cancer cells in escaping therapeutic stress caused by toxic chemotherapy. Therefore, it is necessary to develop ABCG2 inhibitors.. In the present study, we investigated the inhibitory effect of KU55933 on ABCG2 in CRC.. The cytotoxicity assay and drug accumulation assay were used to examine the inhibitory effect of KU55933 on ABCG2. The protein expressions were detected by Western blot assay. The docking assay was performed to predict the binding site and intermolecular interactions between KU55933 and ABCG2.. KU55933 was more potent than the known ABCG2 inhibitor fumitremorgin C to enhance the sensitivity of mitoxantrone and doxorubicin and the intracellular accumulation of mitoxantrone, doxorubicin and rhodamine 123 inside CRC cells with ABCG2 overexpression. Moreover, KU55933 did not affect the protein level of ABCG2. Furthermore, the docking data showed that KU55933 was tightly located in the drug-binding pocket of ABCG2.. In summary, our data presented that KU55933 could effectively inhibit the drug pump activity of ABCG2 in colorectal cancer, which is further supported by the predicted model that showed the hydrophobic interactions of KU55933 within the drug-binding pocket of ABCG2. KU55933 can potently inhibit the activity of ABCG2 in CRC.

Topics: Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily G, Member 2; Cell Line, Tumor; Colorectal Neoplasms; Doxorubicin; Drug Resistance, Neoplasm; Humans; Mitoxantrone; Morpholines; Neoplasm Proteins; Pyrones

Low dose irradiation (LDIR) induces hormesis and adaptive response in organism and mammalian cell lines. Notably, LDIR generates distinct biological effects in cancer cells from normal cells, e.g., it may affect the growth of cancer cells via the activation of certain cell signaling pathway, which does not exist in normal cells. Therefore, LDIR is considered as a promising assistant method of clinical cancer therapy. In this study, we chose human colorectal adenocarcinoma cell line HT-29 as the experimental model, and investigated the differential biological effects between 250 mGy single dose LDIR and 250 mGy intermittent LDIR pretreatments in high dose irradiation (HDIR) radiotherapy and 5-fluorouracil (5-FU) based chemotherapy. Through the cell growth assays, we observed that 250 mGy intermittent LDIR pretreatment significantly increased the killing effect of both radiotherapy and chemotherapy. Western blotting results showed that intermittent LDIR pretreatment apparently activated the ATM/p53 (ataxia telangiectasia mutated, ATM) pathway in radiotherapy; it also activated ERK and p38MAPK pathways in chemotherapy. When we used chemical inhibitors to block the ATM/p53 or p38MAPK pathways, the intermittent LDIR induced cell growth inhibitions were reversed. However, blockage of ERK pathway could not affect the cell growth inhibiton in chemotherapy. Taken together, our findings evaluated the intermittent LDIR as a potential valuable method that can enhance the effectiveness of radiotherapy and chemotherapy, especially in the radio- or chemo-resistant tumor types.

Topics: Adenocarcinoma; Antimetabolites, Antineoplastic; Ataxia Telangiectasia Mutated Proteins; Benzothiazoles; Cell Proliferation; Chemoradiotherapy; Colorectal Neoplasms; Extracellular Signal-Regulated MAP Kinases; Flavonoids; Fluorouracil; HT29 Cells; Humans; Imidazoles; MAP Kinase Signaling System; Morpholines; p38 Mitogen-Activated Protein Kinases; Pyridines; Pyrones; Radiation Dosage; Toluene; Tumor Suppressor Protein p53

Epidemiological and animal studies indicate that selenium supplementation suppresses risk of colorectal and other cancers. The majority of colorectal cancers are characterized by a defective DNA mismatch repair (MMR). Here, we have employed the MMR-deficient HCT 116 colorectal cancer cells and the MMR-proficient HCT 116 cells with hMLH1 complementation to investigate the role of hMLH1 in selenium-induced DNA damage response, a tumorigenesis barrier. The ATM (ataxia telangiectasia mutated) protein responds to clastogens and initiates DNA damage response. We show that hMLH1 complementation sensitizes HCT 116 cells to methylseleninic acid, methylselenocysteine, and sodium selenite via reactive oxygen species and facilitates the selenium-induced oxidative 8-oxoguanine damage, DNA breaks, G(2)/M checkpoint response, and ATM pathway activation. Pretreatment of the hMLH1-complemented HCT 116 cells with the antioxidant N-acetylcysteine or 2,2,6,6-tetramethylpiperidine-1-oxyl or the ATM kinase inhibitor KU55933 suppresses hMLH1-dependent DNA damage response to selenium exposure. Selenium treatment stimulates the association between hMLH1 and hPMS2 proteins, a heterodimer critical for functional MMR, in a manner dependent on ATM and reactive oxygen species. Taken together, the results suggest a new role of selenium in mitigating tumorigenesis by targeting the MMR pathway, whereby the lack of hMLH1 renders the HCT 116 colorectal cancer cells resistant to selenium-induced DNA damage response.

Topics: Acetylcysteine; Adaptor Proteins, Signal Transducing; Adenosine Triphosphatases; Anticarcinogenic Agents; Antioxidants; Ataxia Telangiectasia Mutated Proteins; Cell Cycle Proteins; Cell Line, Tumor; Colorectal Neoplasms; Cysteine; DNA Breaks; DNA Mismatch Repair; DNA Repair Enzymes; DNA-Binding Proteins; Drug Resistance, Neoplasm; Guanosine; Humans; Mismatch Repair Endonuclease PMS2; Morpholines; MutL Protein Homolog 1; Nuclear Proteins; Organoselenium Compounds; Piperidines; Protein Serine-Threonine Kinases; Pyrones; Reactive Oxygen Species; Selenocysteine; Sodium Selenite; Tumor Suppressor Proteins