Search results for "drug resistance"
showing 10 items of 953 documents
Acquired resistance of melanoma cells to the antineoplastic agent fotemustine is caused by reactivation of the DNA repair gene mgmt
2001
Acquired resistance to antineoplastic agents is a frequent obstacle in tumor therapy. Malignant melanoma cells are particularly well known for their unresponsiveness to chemotherapy; only about 30% of tumors exhibit a transient clinical response to treatment. In our study, we investigated the molecular mechanism of acquired resistance of melanoma cells (MeWo) to the chloroethylating drug fotemustine. Determination of O6-methylguanine-DNA methyltransferase (MGMT) activity showed that MeWo cells that acquired resistance to fotemustine upon repeated treatment with the drug display high MGMT activity, whereas the parental cell line had no detectable MGMT. The resistant cell lines exhibit cross-…
Apoptotic effects of thiazolobenzimidazole derivatives on sensitive and multidrug resistant leukaemic cells
2001
We investigated the cytotoxic activity of eight thiazolobenzimidazole derivatives on sensitive HL60 and multidrug-resistant (MDR) (HL60R) leukaemia cell lines. The antitumour effects of these compounds were compared with those of RS-TBZ, a thiazolobenzimidazole derivative, previously described in our reports, that was able to induce apoptosis more markedly in MDR cells than in the parental sensitive cell lines. Only two compounds in this study proved to have interesting effects: (a) the S-enantiomer of TBZ, that was able to induce apoptosis in MDR cells in a slightly more selective manner than TBZ (racemic form); and (b) TBZ-4-OCH3 (TBZ-4-OCH3), that showed cytotoxic and apoptotic effects o…
Temporal molecular and biological assessment of an erlotinib-resistant lung adenocarcinoma model reveals markers of tumor progression and treatment r…
2012
Abstract Patients with lung cancer with activating mutations in the EGF receptor (EGFR) kinase, who are treated long-term with tyrosine kinase inhibitors (TKI), often develop secondary mutations in EGFR associated with resistance. Mice engineered to develop lung adenocarcinomas driven by the human EGFR T790M resistance mutation are similarly resistant to the EGFR TKI erlotinib. By tumor volume endpoint analysis, these mouse tumors respond to BIBW 2992 (an irreversible EGFR/HER2 TKI) and rapamycin combination therapy. To correlate EGFR-driven changes in the lung with response to drug treatment, we conducted an integrative analysis of global transcriptome and metabolite profiling compared wit…
Broad-spectrum Cross-resistance to Anticancer Drugs Mediated by Epidermal Growth Factor Receptor
2019
BACKGROUND The oncogenic role of epidermal growth factor receptor (EGFR) has been intensively studied. However, its emerging role in drug resistance has not been fully addressed. MATERIALS AND METHODS This study systematically investigated the correlation of mRNA and protein expression of EGFR, as well as gene amplification and mutations with the log-transformed half-maximal inhibitory concentration (log10IC50) values obtained from the NCI panel of 60 human tumor cell lines against 83 standard anticancer agents and the top 10 natural cytotoxic products previously screened by us. RESULTS EGFR protein expression, rather than other measurements, was most frequently associated with drug respons…
Altered Expression of c-IAP1, Survivin, and Smac Contributes to Chemotherapy Resistance in Thyroid Cancer Cells
2006
Abstract Resistance to chemotherapy predicts an unfavorable outcome for patients with radioiodine-insensitive thyroid cancer. To investigate the mechanisms underlying this resistance, we evaluated the expression of four different inhibitor of apoptosis proteins, and their antagonist, Smac, in thyroid cancer cells that survived 48 hours of exposure to cisplatin, doxorubicin, or taxol. We found high levels of c-IAP1 after cisplatin treatment and increased expression of survivin following exposure to doxorubicin. Cells that endured treatment with taxol showed reduced expression of Smac and released minimal amounts of this protein from the mitochondria. Down-regulation of c-IAP1 and survivin in…
The dual PI3K/mTOR inhibitor PKI-587 enhances sensitivity to cetuximab in EGFR-resistant human head and neck cancer models
2014
Background:Cetuximab is the only targeted agent approved for the treatment of head and neck squamous cell carcinomas (HNSCC), but low response rates and disease progression are frequently reported. As the phosphoinositide 3-kinase (PI3K) and the mammalian target of rapamycin (mTOR) pathways have an important role in the pathogenesis of HNSCC, we investigated their involvement in cetuximab resistance.Methods:Different human squamous cancer cell lines sensitive or resistant to cetuximab were tested for the dual PI3K/mTOR inhibitor PF-05212384 (PKI-587), alone and in combination, both in vitro and in vivo.Results:Treatment with PKI-587 enhances sensitivity to cetuximab in vitro, even in the co…
Development of resistance towards artesunate in MDA-MB-231 human breast cancer cells.
2011
Breast cancer is the most common cancer and the second leading cause of cancer death in industrialized countries. Systemic treatment of breast cancer is effective at the beginning of therapy. However, after a variable period of time, progression occurs due to therapy resistance. Artesunate, clinically used as anti-malarial agent, has recently revealed remarkable anti-tumor activity offering a role as novel candidate for cancer chemotherapy. We analyzed the anti-tumor effects of artesunate in metastasizing breast carcinoma in vitro and in vivo. Unlike as expected, artesunate induced resistance in highly metastatic human breast cancer cells MDA-MB-231. Likewise acquired resistance led to abol…
Histone deacetylase inhibition by valproic acid down-regulates c-FLIP/CASH and sensitizes hepatoma cells towards CD95-and TRAIL receptor-mediated apo…
2005
Hepatocellular carcinoma (HCC) is highly resistant to chemotherapy, leading to a poor prognosis of advanced disease. Inhibitors of histone deacetylase (HDACi) induce re-differentiation in tumor cells and thereby re-establish sensitivity towards apoptotic stimuli. HDACi are entering the clinical stage of tumor treatment, and several substances are currently being tested in clinical trials to prove their efficacy in the treatment of leukemias and solid tumors. In this study, we investigated the impact of the HDACi valproic acid (VA) on TRAIL- and CD95-mediated apoptosis in hepatoma cells, as well as its sensitizing effect on a chemotherapeutic agent. Treatment of HepG2 cells with VA increased…
Downregulation of RhoB GTPase confers resistance to cisplatin in human larygneal carcinoma cells
2009
Acquired resistance to cisplatin represents a major obstacle to an efficient chemotherapy. We found downregulation of RhoB expression in cisplatin-resistant tumor cell lines from different origin. In cisplatin-resistant laryngeal carcinoma subline overexpression of farnesylated or geranylgeranylated RhoB increased cisplatin-induced cell death, while silencing of RhoB expression diminished sensitivity of parental HEp-2 cells via decreased cellular accumulation of cisplatin. However, since RhoB silencing in additional tumor cell lines did not alter their sensitivity to cisplatin, we can assume that RhoB downregulation does not provide general protective role in cell response to cisplatin. Nev…
The apoptotic effects of cisplatin and carboplatin in retinoblastoma Y79 cells.
1998
This study demonstrated that cisplatin and carboplatin stimulate apoptosis in human retinoblastoma Y79 cells, cisplatin being the most effective compound. The apoptotic effect appeared after 8 h and then increased in a time-dependent manner. Treatment with cisplatin and carboplatin also provoked an increase in the level of p53 and p21, and a lowering in Bcl-2. The prolonged exposure of Y79 cells to cisplatin induced resistance to cisplatin, carboplatin and etoposide. The basal level of p53 was in resistant cells higher than in untreated cells, while Bcl-2 was not modified. p53 and Bcl-2 levels did not change after treating of resistant cells with cisplatin, carboplatin or etoposide. However…