Search results for "drug resistance"

Resistance to diverse apoptotic triggers in multidrug resistant HL60 cells and its possible relationship to the expression of P-glycoprotein, Fas and…

2002

We studied the human HL60 leukemia cell line and its multidrug resistant (MDR) variant HL60R. In contrast to the HL60, HL60R showed an inability to undergo apoptosis from doxorubicin (Dox) or other different stimuli, including cisplatin, Fas ligation and serum withdrawal. HL60R cells lost surface Fas expression, but we found no evidence that Fas/FasL mediates the apoptotic effects of Dox in HL60. P-glycoprotein (P-gp) did not seem to play a major role as a specific inhibitor of apoptosis. In fact, the P-gp inhibitor verapamil reversed only partially the resistance to Dox-induced apoptosis of the MDR cells. In addition, it did not modify the rate of apoptosis induced from the other stimuli i…

Galangin increases the cytotoxic activity of imatinib mesylate in imatinib-sensitive and imatinib-resistant Bcr-Abl expressing leukemia cells

2008

Resistance to imatinib mesylate is an emergent problem in the treatment of Bcr-Abl expressing myelogenous leukemias and additional therapeutic strategies are required. We observed that galangin, a non-toxic, naturally occurring flavonoid was effective as anti-proliferative, and apoptotic agent in Bcr-Abl expressing K562 and KCL22 cells and in imatinib mesylate resistant K562-R and KCL22-R cells. Galangin induced an arrest of cells in G0–G1phase of cell cycle and a decrease in pRb, cdk4, cdk1, cycline B levels; moreover, it was able to induce a monocytic differentiation of leukemic Bcr-Abl+ cells. Of note, galangin caused a decrease in Bcl-2 levels and markedly increased the apoptotic activi…

In vivo effects of tumor necrosis factor-α or flavone acetic acid in combination with doxorubicin on multidrug-resistant B16 melanoma

1996

Having observed that tumor necrosis factor (TNF)-alpha and doxorubicin (DXR) produce a synergistic inhibition of melanoma B16 and also of its multidrug resistant (MDR) variant in vitro, we tested whether this interaction would occur in vivo as well. C57BL/6 mice with s.c. tumors were treated with TNF or flavone acetic acid (FAA), a biological response modifier, in simultaneous or sequential combination with DXR. The agents were administered systemically. Overall, the results were negative, apart from a trend towards slight synergy, found in the chemosensitive melanoma, when TNF was given 1 or 2 days before DXR. The effects of FAA and DXR were found to be subadditive or antagonistic. However…

MUC1 oncoprotein promotes refractoriness to chemotherapy in thyroid cancer cells.

2007

Abstract Overexpression of MUC1 oncoprotein is frequently observed in cancer and contributes to confer resistance to genotoxic agents. Papillary, follicular, and anaplastic thyroid carcinomas are the three forms of thyroid epithelial cancer. Anaplastic tumors are less differentiated and extremely aggressive, characterized by a poor prognosis. Little is known about the role of MUC1 in thyroid cancer. We recently showed that autocrine production of interleukin (IL)-4 and IL-10 controls thyroid cancer cell survival, growth, and resistance to chemotherapy through activation of Janus-activated kinase/signal transducers and activators of transcription (JAK/STAT) and phosphatidylinositide 3′-OH ki…

Carboxyamidotriazole inhibits cell growth of imatinib-resistant chronic myeloid leukaemia cells including T315I Bcr-Abl mutant by a redox-mediated me…

2010

Mutation of the Bcr–Abl oncoprotein is one of most frequent mechanisms by which chronic myelogenous leukemia (CML) cells become resistant to imatinib. Here, we show that treat- ment of cell lines harbouring wild type or mutant BCR–ABL with carboxyamidotriazole (CAI), a calcium influx and signal transduction inhibitor, inhibits cell growth, the expres- sion of Bcr–Abl and its downstream signalling, and induces apoptosis. Moreover, we show that CAI acts by increasing intracellular ROS. Clinically significant, CAI has also inhibitory effects on T315I Bcr–Abl mutant, a mutation that causes CML cells to become insensitive to imatinib and second generation abl kinase inhibitors.

Abstract LB-099: Metabolic vulnerabilities of mesenchymal-like EGFR-mutant NSCLC cells with acquired resistance to tyrosine kinase inhibitors

2018

Abstract Despite the availability of the effective targeted therapies in lung cancer, such as EGFR tyrosine kinase inhibitors (TKIs), drug tolerance and acquired resistance are two common problems that negatively impact lung cancer patient survival. Consequently it is important to understand the molecular basis of the drug tolerance and resistance so that we could formulate effective strategies to ameliorate the efficacy of existing drug and to suppress the emergence of drug resistance. A burgeoning body of literature demonstrated that epigenetic changes by the methylation of DNA and histones are critical in acquired drug resistance, especially in those cancer cells with stem cell-like prop…

Immune escape of AKT overexpressing ovarian cancer cells

2012

Platinum-resistance is the most crucial problem for treatment of ovarian cancer. There is a clinical need for new treatment strategies which overcome platinum resistance. As survival is strongly influenced by immunological parameters, immunotherapeutic strategies appear promising. Therefore a better understanding of the interaction between ovarian tumour cells and cells of the immune system is a necessary prerequisite. In the present study we aimed to enlighten the interactions between platinum resistant and platinum sensitive ovarian cancer cells and natural-killer (NK)-cells. Modified FATAL assay was used for determining the killing efficiency of NK-cells for the parental A2780 cells and …

Resistance factors in colon cancer tissue and the adjacent normal colon tissue: glutathione S-transferases alpha and pi, glutathione and aldehyde deh…

1998

Abstract Glutathione S -transferases (GST) α and π , glutathione (GSH) and aldehyde dehydrogenase (ADH) were determined in colorectal cancer tissue specimens and in the adjacent normal colon tissue. The median contents in normal and cancer tissue were 8.1 (2.3–30.3) (5–95% quantiles) and 15.1 (5.3–50.3) μ g/mg protein for GST π ( P =0.035), 0.0 (0.0–1.4) and 0.4 (0.0–3.5) μ g/mg protein for GST α ( P =0.019), 7.3 (1.3–22.7) and 5.6 (2.3–26.0) μ g/mg protein for GSH ( P =0.171) and 30.8 (13.0–42.0) and 23.2 (9.0–32.9) μ g/mg protein for ADH ( P =0.0017), respectively. Thus, the mean GST α and π both significantly increased in colon cancer compared to the adjacent normal tissue, which underli…

Scientific Proceedings Second International Symposium on Cytostatic Drug Resistance

1991

Role of the progesterone receptor for paclitaxel resistance in primary breast cancer

2007

Paclitaxel plays an important role in the treatment of primary breast cancer. However, a substantial proportion of patients treated with paclitaxel does not appear to derive any benefit from this therapy. We performed a prospective study using tumour cells isolated from 50 primary breast carcinomas. Sensitivity of primary tumour cells to paclitaxel was determined in a clinically relevant range of concentrations (0.85-27.2 microg ml(-1) paclitaxel) using an ATP assay. Chemosensitivity data were used to study a possible association with immunohistochemically determined oestrogen and progesterone receptor (ER and PR) status, as well as histopathological parameters. Progesterone receptor (PR) m…