RESUMO
Protein phosphatases play critical roles in regulating cell division, cell apoptosis, and cell cycle in eukaryotic cells, participating in numerous signal transduction processes and exerting a large amount of significant biological functions. A variety of protein phosphatases are identified to maintian the phosphorylation level of key proteins with a moderate level in the antiviral innate immune response to virus infectioa In this paper, we reviewed the roles of serine/threonine protein phosphatases, tyrosine protein phosphatases, and lipid phosphatases in regulating antiviral innate immune responses.
RESUMO
Arsenic trioxide (ATO) is used as a chemotherapeutic agent for the treatment of acute promyelocytic leukemia. However, increasing drug resistance is reducing its efficacy. Therefore, a better understanding of ATO resistance mechanism is required. In this study, we established an ATO-resistant human epidermoid carcinoma cell line, KB/ATO, from its parental KB-3-1 cells. In addition to ATO, KB/ATO cells also exhibited cross-resistance to other anticancer drugs such as cisplatin, antimony potassium tartrate, and 6-mercaptopurine. The arsenic accumulation in KB/ATO cells was significantly lower than that in KB-3-1 cells. Further analysis indicated that neither application of P-glycoprotein inhibitor, breast cancer resistant protein (BCRP) inhibitor, or multidrug resistance protein 1 (MRP1) inhibitor could eliminate ATO resistance. We found that the expression level of ABCB6 was increased in KB/ATO cells. In conclusion, ABCB6 could be an important factor for ATO resistance in KB/ATO cells. The ABCB6 level may serve as a predictive biomarker for the effectiveness of ATO therapy.
RESUMO
Multidrug resistance (MDR), defined as the resistance of cancer cells to compounds with diverse structures and mechanisms of actions, significantly limits the efficacy of antitumor drugs. A major mechanism that mediates MDR in cancer is the overexpression of adenosine triphosphate (ATP)-binding cassette transporters. These transporters bind to their respective substrates and catalyze their efflux from cancer cells, thereby lowering the intracellular concentrations of the substrates and thus attenuating or even abolishing their efficacy. In addition, cancer cells can become resistant to drugs via mechanisms that attenuate apoptosis and cell cycle arrest such as alterations in the p53, check point kinase, nuclear factor kappa B, and the p38 mitogen-activated protein kinase pathway. In this review, we discuss the mechanisms by which β-elemene, a compound extracted from Rhizoma zedoariae that has clinical antitumor efficacy, overcomes drug resistance in cancer.