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At least 19 recordsLinked to original sources
PubMed2006

[Effect of down-regulation of survivin gene on apoptosis and cisplatin resistance in cisplatin resistant human lung adenocarcinoma A549/CDDP cells].

OBJECTIVE: To investigate the effects of survivin antisense oligodeoxynucleoties (ASODN) transfection mediated by cytofectin on apoptosis and cisplatin resistance in cisplatin resistant human lung adenocarcinoma A549/CDDP cells in vitro. METHODS: A549/CDDP cells were cultured routinely in RPMI-1640 medium. Survivin ASODN mediated by cytofectin was transfected into the A549/CDDP cells. Reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry SABC assays were performed to determine the regulation of survivin expression by ASODN. The influence of ASODN transfection on apoptosis was determined by fluoroscence microscopy and Hoechst staining, agarose gel electrophoresis, flow cytometry and caspase-3 colorimetric assay. MTT assay was performed to detect the cell viability, half-maximum inhibitory concentration (IC50) and cisplatin resistance index (RI) were thereby calculated. RESULTS: Transfected by survivin ASODN for 48 h, down-regulation of survivin expression was measured, of which mRNA and protein expression was significantly down-regulated to 41.56% and 0.864 +/- 0.045, respectively (P < 0.05). Transfection with survivin ASODN caused typical apoptotic changes, including characteristic chromatin condensation, nuclear shrinkage, nuclear cleavage and the cells grew more regularly, and some cells were floating. Typical DNA ladder pattern was observed by agarose gel electrophoresis. Furthermore, apoptotic index and caspase-3 activity was enhanced to 34.03% and 1.1298 +/- 0.2502, respectively (P < 0.05). It was significantly different as compared with the control group. While combination with ASODN and 10 micromol/L cisplatin caused far more distinctive apoptotic alterations, of which AI and caspase-3 activity reached to 65.85% and 1.6805 +/- 0.2758, respectively (P < 0.05), and even compared with the single ASODN group, the difference was still significant (P < 0.05). Transfected with survivin ASODN only or with combination of cisplatin for 48 h, the inhibitory rate of cell growth was enhanced to 59.3% and 83.7% (P < 0.05), respectively, while inversely, the cell viability reduced to a lowest value. The half-maximum inhibitory concentration of cisplatin was reduced from 225.03 +/- 10.59 micromol/L to 158.84 +/- 4.26 micromol/L, and the resistant index was conversely reduced from 11.9 to 8.39. Non-sense oligodeoxynucleotides (NSODN) and liposome had no effect on the cells growth (P > 0.05). CONCLUSION: Transfection with survivin ASODN can to a great extent reverse the cisplatin resistance in human cisplatin resistant lung adenocarcinoma cells A549/CDDP in vitro, and can thereby significantly inhibit the growth of the cells. The mechanism of reversal of resistance to cisplatin by this transfection can be associated with specific down-regulation of survivin expression, which decreases the threshold of apoptosis, induces more pronounced apoptosis,and reverses the resistance to apoptosis induced by cisplatin in A549/CDDP cells in vitro.

Adenocarcinoma↗
PubMed2003

Inhibition of glutathione synthesis reverses Bcl-2-mediated cisplatin resistance.

Cisplatin is a potent cytotoxic agent that functions as a bivalent electrophile, forming both interstrand and intrastrand DNA cross-links. Cisplatin-mediated DNA damage results in cell cycle arrest and initiation of apoptotic cell death. Increased cellular glutathione concentrations have been closely correlated with cisplatin resistance but do not reduce the extent of cisplatin-DNA adduct formation. One hypothesis to explain the ability of glutathione to inhibit cisplatin cytotoxicity is that glutathione, through its antioxidant function, plays a role in apoptotic regulatory pathways. We tested this hypothesis using MCF-7 breast cancer cells transfected with the apoptotic inhibitor Bcl-2. Bcl-2 overexpression in MCF-7 cells was associated with a nearly 3-fold increase in cellular glutathione levels and with increased resistance to cell death after cisplatin exposure. Treatment of MCF-7 lines with buthionine sulfoximine, an inhibitor of glutathione synthesis, normalized glutathione levels in Bcl-2 and control transfectants and completely abrogated Bcl-2-mediated cisplatin resistance without affecting Bcl-2 expression. Bcl-2 overexpression and up-regulation of glutathione were not associated with a change in either cisplatin-DNA adduct formation or repair over time. These results suggest that Bcl-2-mediated cisplatin resistance in MCF-7 cells is dependent on up-regulation of glutathione production, which contributes to cell survival by mechanisms independent of cisplatin inactivation or inhibition of DNA adduct formation. A similar dependence on glutathione for Bcl-2-mediated inhibition of cisplatin toxicity was confirmed in a second cell line, the lymphocytic precursor FL5.12. Taken together, these data suggest that apoptotic signaling after genotoxic exposure can be inhibited by the antioxidant activity of glutathione. Inhibition of glutathione synthesis or modulation of glutathione stores in tumors that overexpress Bcl-2 may comprise a novel anticancer strategy.

Antineoplastic Agents↗
PubMed2004

Role of the transcription factor Ets-1 in cisplatin resistance.

Cisplatin is a DNA damaging agent widely used as a chemotherapeutic agent. A major limitation of the use of this agent is the development of drug resistance within tumors. Several in vitro models exist which enable the investigation of resistance mechanisms, including 2008/C13* ovarian carcinoma cells. C13* cells are variants of 2008 cells, displaying cisplatin resistance following 13 consecutive cisplatin treatments. This model system has led to the identification of several mechanisms that play parts in the multifactorial nature of cisplatin resistance. In this study, we have examined the contribution of a transcription factor, Ets-1, to the cisplatin resistance of C13* cells. Ets-1 is up-regulated in C13* cells as compared with the cisplatin-sensitive 2008 cells and overexpression of this protein in 2008 cells led to a 7-fold increase in resistance. Further studies on a colorectal carcinoma cell line overexpressing Ets-1 indicated that this phenomenon is not cell specific-increased cisplatin resistance correlated to Ets-1 expression. The mechanism of cisplatin resistance elicited by Ets-1 is potentially via transcriptional activation of genes whose products have well-described functions in reducing cisplatin toxicity. Examples, identified via microarray analysis, include metallothioneins and DNA repair enzymes. This is the first report to our knowledge associating expression of Ets-1, a transcription factor whose expression often signals poor prognosis in various cancer types, to cisplatin resistance.

Animals↗
PubMed1998

Cellular and molecular determinants of cisplatin resistance.

Cisplatin and carboplatin are among the most active and widely used cytotoxic anticancer drugs. However, the acquisition or presence of resistance significantly undermines the curative potential of these drugs against many malignancies. Multiple potential mechanisms of resistance have been identified at the cellular and molecular levels. Alterations in cellular pharmacology, including decreased drug accumulation, increased cellular thiol levels and increased repair of platinum-DNA damage, have been observed in numerous model systems. More recently, it has become apparent that an enhanced capacity to tolerate cisplatin-induced damage may also contribute to resistance. Alterations in proteins that recognise cisplatin-DNA damage (mismatch repair and high-mobility group (HMG) family proteins) and in pathways that determine sensitivity to apoptosis may contribute to damage tolerance. It remains to be determined whether any of these mechanisms contribute significantly to resistance in the clinical setting. Ongoing biochemical modulation and translational correlative trials should clarify which specific mechanisms are most relevant to clinical cisplatin resistance. Such investigations have the potential to improve the ability to predict likelihood of response and should identify potential targets for pharmacological or molecular intervention.

Antineoplastic Agents↗
PubMedDate not supplied

Different roles for K+ channels in cisplatin-resistant cell lines argue against a critical role for these channels in cisplatin resistance.

Cisplatin resistance has been associated with altered K+ fluxes. Here, we focused our investigations on the detection of K+ channels in a series of cisplatin-resistant (CP-r) cells with increasing resistance and on the functional relationship of these K+ channels to resistance. Microarray analysis and confocal microscopy indicated that there was overexpression of the ether-a-gogo gene (HERG) and the inwardly rectifying potassium channel gene (TWIK) in a human epidermal KB and human liver BEL-7404 carcinoma cell line series selected for cisplatin resistance. With increased resistance, the plasma membrane potential, but not the mitochondrial membrane potential, also increases in these two series. For these reasons, we conducted cell proliferation studies in the presence of either antibodies directed against the detected K+ channels, omeprazole (a H+ pump inhibitor) or a specific inhibitor of the HERG channel (WAY-123398-A-5). The antibodies and omeprazole influenced cell growth only very slightly. The specific K+ channel blocker did not alter cisplatin resistance. We also observed that manipulation of K+ fluxes with antibodies and the H+ pump with omeprazole resulted in opposite effects on cisplatin resistance in these two cell lines. We conclude that K+ and H+ homeostasis are not critical factors in cisplatin resistance since they affect cisplatin resistance differently in KB and BEL-7404 cells.

Antineoplastic Agents↗
PubMed1996

Cross-resistance, cisplatin accumulation, and platinum-DNA adduct formation and removal in cisplatin-sensitive and -resistant human hepatoma cell lines.

The BEL7404 human hepatoma cell line was selected in vitro for primary cisplatin resistance. A panel of four cisplatin-resistant sublines were generated which exhibited resistance to cisplatin (up to 34-fold) but were not cross-resistant to adriamycin, taxol, etoposide, or mitomycin C. Further characterization of this panel of cell lines revealed that increased cisplatin resistance was associated with decreased cisplatin accumulation in the selected sublines (up to 14-fold) relative to the parental BEL7404 cell line. A significant reduction in platinum-DNA adduct formation (9-fold) and ribosomal RNA gene-specific interstrand crosslink formation (12-fold) were also observed in the 7404-CP20 cell line. No differences in the rate of platinum efflux from the BEL7404 and 7404-CP20 cell lines were detected following a 4-h loading period, and total platinum-DNA adduct and gene-specific interstrand crosslink removal rates were similar in both cell lines. There were approximately 3-fold more total platinum-DNA adducts present in the BEL7404 cells relative to the 7404-CP20 cells at equitoxic concentrations of cisplatin, suggesting that DNA damage tolerance also contributes to the cisplatin resistance phenotype. Overall, these results indicate that decreased cisplatin accumulation is the major cisplatin resistance mechanism present in the in vitro-selected cell lines. This model system of acquired cisplatin resistance may be valuable in determining the molecular basis for decreased cisplatin uptake and be useful for the study of potential resistance modulators.

Carcinoma, Hepatocellular↗
PubMed2006

A high nuclear basal level of ERK2 phosphorylation contributes to the resistance of cisplatin-resistant human ovarian cancer cells.

OBJECTIVE: The aim of this study was to elucidate the role of ERK1/2 on cisplatin resistance in human ovarian cancer cells. METHODS: The relationship between nuclear levels of ERK2 and cisplatin-induced apoptosis in human ovarian carcinoma cell line, OVCAR-3, and in cells of the cisplatin-resistant subclone, OVCAR-3/CDDP, was examined using immunoblotting and immunocytochemistry. RESULTS: Cisplatin treatment resulted in the activation of ERK2, both in OVCAR-3 and OVCAR-3/CDDP cells. However, considerable levels of activated ERK2 existed in the nuclei of OVCAR-3/CDDP cells during serum starvation and in the early period (1-3 h) after cisplatin treatment. Conversely, phospho-ERK2 was marginally detected in the nuclei of OVCAR-3 cells prior to cisplatin treatment. These phenomena were confirmed by immunofluorescence staining of the phosphorylated ERK2 in the nuclei of both cells. High basal phospho-ERK2 in the nuclei of OVCAR-3/CDDP cells contributed to cisplatin resistance, and was supported by several observations; (1) treatment of U0126, an inhibitor of MEK/ERK signaling pathway, partially sensitized OVCAR-3/CDDP cells to cisplatin; (2) pretreatment of OVCAR-3 cells with phorbol 12-myristate 13-acetate (PMA), an activator of ERK, induced nuclear translocation of activated ERK2, which led to the suppression of cisplatin-induced apoptosis. CONCLUSIONS: These results collectively indicate that prelocalization of activated ERK2 in the nuclei contribute to cisplatin resistance in OVCAR-3/CDDP cells.

Antineoplastic Agents↗
PubMed2003

Radiosensitivity in multidrug-resistant and cisplatin-resistant human carcinoma cell lines.

The radiosensitivity of a multidrug-resistant (MDR) clone and a cisplatin-resistant clone was compared with that of their parental chemosensitive cell lines. The LoVo cell line was derived from a human colon carcinoma, and LoVo-R was the MDR clone. The MDR phenotype is attributable to an increased drug efflux mediated by the P-glycoprotein and involves several classes of structurally unrelated drugs. The 2008 cell line was derived from a human ovary carcinoma and C13 was the cisplatin-resistant clone. Reduced cisplatin accumulation and elevated plasma membrane potential partially account for the drug resistance of C13 cells. The chemoresistance of LoVo-R and C13 cells was confirmed by cytotoxicity tests consisting of 24-hour paclitaxel and 1-hour cisplatin incubation, respectively. The radiosensitivity was evaluated by a clonogenic test. The dose-reducing cell survival fraction from 1 to 0.37 (D(0)), the quasi-threshold dose (Dq), and the survival fraction (SF) after 2 or 4 Gy were determined for each cell line. D(0), Dq, and SF(2) were 1.3 +/- 0.4 Gy, 2.1 +/- 0.6 Gy, and 43 +/- 4% for the LoVo cell line and 1.0 +/- 0.2 Gy, 1.7 +/- 0.4 Gy, and 45 +/- 8%, respectively, for the LoVo-R cell line. D(0), Dq, and SF(4) were 1.7 +/- 0.3 Gy, 3.1 +/- 0.4 Gy, and 43 +/- 12% for 2008 cells and 2.6 +/- 0.5 Gy, 4.3 +/- 0.6 Gy, and 53 +/- 11%, respectively for C13 cells. No significant differences were found between LoVo and LoVo-R cells, whereas C13 cells showed a significantly greater D(0,) Dq, and SF(4) than 2008 cells (p <0.05). Incubation of 2008 and C13 cells with subcytotoxic buthionine (BSO) before and after irradiation partially restored C13 radiosensitivity. In fact, D(0) dropped from 2.8 +/- 0.1 to 2.0 +/- 0.3 Gy in C13 cells with and without BSO, whereas it was 1.9 +/- 0.2 Gy in 2008 cells in the absence and presence of BSO. The total glutathione content (GSH) of C13 cells was 1.5-fold higher than that of 2008 cells. BSO treatment caused a partial depletion of GSH in 2008 and C13 cells, but their radiosensitivity did not change accordingly.

Cell Line, Tumor↗
PubMed2000

Co-transfection of MRP and bcl-2 antisense S-oligodeoxynucleotides reduces drug resistance in cisplatin-resistant lung cancer cells.

OBJECTIVE: To detect the influence of antisense s-oligodeoxynucleotides (S-ODNs) of bd-2 and multidrug resistance-associated protein (MRP) genes multidrug resistance-associated protein gene and bcl-2 antisense S-oligodeoxynucleotides on cisplatin-resistant lung adenocarcinoma cell line A549DDP which overexpresses both bcl-2 and MRP. METHODS: A549DDP cells were treated with sense and antisense S-ODN mediated by lipofection. Expression of MRP and bcl-2 mRNA and protein in the treated cells was measured by RT-PCR and flow cytometry (FCM), respectively. Apoptosis was identified by DNA electrophoresis and terminal deoxynucleotidyl transferase (TdT)-mediated biotin dUTP nick end-labeling (TUNEL). The degree of drug resistance of the treated cells was detected by a cell viability 3'-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyl-tefrazolium bromide thiazolylblue (MTT) assay. RESULTS: Expression of bcl-2 and MRP significantly decreased in the cells treated with bcl-2 or/and MRP antisense S-ODN for 48 h as compared to the cells untreated and sense-treated (P < 0.05). Resistance to cisplatin in the cells treated with bcl-2 or/and MRP antisense S-ODN decreased by 60.6% (6.5 times), 56.4% (7.2 times) and 71.0% (4.8 times), respectively, which paralleled the decrease of bcl-2 and MRP expression. Similarly, the resistance to etoposide and epirubicin in antisense-treated cells also reduced in parallel to decreases of the two gene expressions. The drug resistance in sense-treated cells was similar to that in untreated cells. Statistically significant dose- and concentration-dependent increases of apoptotic cells were observed in the groups exposed to 100 mumol/L cisplatin for 48 h after treatment by bcl-2 or/and MRP antisense. CONCLUSION: Bcl-2 and MRP were at least additive and possibly synergistic in conferring drug resistance in a cisplatin-resistant lung adenocarcinoma cell line. Antisense S-ODN could attenuate drug resistance by promoting cells apoptosis, which might lead to a new treatment for patients with non-small cell lung cancers (NSCLCs) who are refractory to conventional chemotherapy.

Adenocarcinoma↗
PubMed2004

Biological effects of ultrasound exposure on adriamycin-resistant and cisplatin-resistant human ovarian carcinoma cell lines in vitro.

Human ovarian cancer cell lines, SKOV3 and its adriamycin-resistant substrain SKOV3/ADR and COC1 and its cisplatin-resistant substrain COC1/DDP, were subjected to acoustic exposure. The critical levels (LC), which resulted in no immediate cell killing, were determined in four cell lines, respectively. LC were the same in four cell lines. After being insonated by LC, cell proliferation and clone forming of SKOV3/ADR were suppressed but those of SKOV3 were not affected (1); cell reproduction of COC1 was triggered but that of COC1/DDP was not influenced (2); flow cytometry detected sub-G1 peaks in SKOV3/ADR and COC1/DDP (3). These findings suggested that there were differences in the responses to ultrasound exposure between chemosensitive and chemoresistant human ovarian cancer cells.

Cell Division↗
PubMed1997

Expression and intracellular localization of heat shock proteins in multidrug resistance of a cisplatin resistant human ovarian cancer cell line.

TYK-R10 is a cisplatin resistant human ovarian carcinoma cell line and showed a cross resistance to various anti-cancer drugs including adriamycin (ADR), vincristine (VCR) and etoposide, despite a lack of multidrug phenotype. Under normal conditions, various heat shock proteins (HSPs) were expressed in TYK-R10 but not in parental line (TYK-nu). Non-lethal short-term heat shock treatment induced a high tolerance for cisplatin and VCR in TYK-R10 and ADR, and VCR in TYK-nu. This treatment induced and/or enhanced the expression of various types of HSPs in various intracellular localizations in both TYK-R10 and TYK-nu, with minor differences. These findings indicate that combined expression and intracellular localization of HSPs may play an important role in drug resistance of TYK-R10.

Cisplatin↗
PubMedDate not supplied

Ultrastructure alterations in adriamycin-resistant and cisplatin-resistant human ovarian cancer cell lines exposed to nonlethal ultrasound.

Human ovarian cancer cell lines, SKOV3 and its adriamycin-resistant substrain SKOV3/ADR and COC1 and its cisplatin-resistant substrain COC1/DDP, were exposed to nonlethal ultrasound. Ultrastructures in sham-insonated and insonated cells were inspected by transmission electron microscopy, and cytochrome C in cytosol was determined by enzyme-linked immunosorbent assay. Ultrasound exposure led to no significant changes in SKOV3/ADR cells, but tumid mitochondria occurred in SKOV3 cells. Mitochondria changes were also detected in some exposed COC1 and COC1/DDP cells. Apoptotic bodies could be detected in either control or insonated COC1/DDP cells. A few exposed COC1/DDP cells became reticular. Cytochrome C in cytosol in exposed SKOV3/ADR cells was increased but that in exposed COC1/DDP cells was decreased. These findings revealed that the bioeffect of ultrasound on chemosensitive cells was not identical to that of chemoresistant ones, and ultrasound was a potential approach for treatment of drug-resistant ovarian cancers.

Antibiotics, Antineoplastic↗
PubMed1993

[Detection of drug resistant-genes in cisplatin-resistant colon carcinoma cells by RT-PCR assay. II].

The c-fos, c-Ha-ras and c-myc oncogenes have been proposed to play an important role in DNA synthesis. Expression of c-fos, c-Ha-ras and c-myc genes were compared with the human colon carcinoma cell line HCT8S cells and a subline that was 4.5 resistant to cis-diamminedichloro-platinum (cisplatin). Resistant cells (HCT8DDP) exhibited a 4.0, 2.8 and 1.1 fold in mRNA for these genes when compared with the parent cells by Northern blotting analysis, respectively. The reverse transcription (RT)-PCR method has been demonstrated to quantify a sequence of these oncogenes. This method allowed the detection of gene expression from minimal cells. Thus RT-PCR assay could be an effective device in th early detection of oncogenes to cisplatin-resistance.

Base Sequence↗
PubMed2002

Non-cross resistance of ZD0473 in acquired cisplatin-resistant lung cancer cell lines.

ZD0473 is a new generation platinum agent that, in preclinical studies, shows evidence of an extended spectrum of anti-tumor activity and overcomes platinum resistance mechanisms. The drug contains a bulky methylpyridine ligand at its platinum center, which is responsible for its ability to overcome platinum resistance. We examined the growth inhibitory effects of ZD0473 in human lung cancer cell lines resistant to cisplatin in vitro. Four cisplatin resistant human lung cancer cell lines (PC-14/CDDP, SBC-3/CDDP, PC-9/CDDP, H69/CDDP) showed the expected resistance to cisplatin but were non-cross, or much less, resistant to ZD0473, as determined by an MTT assay. A reduction in the intracellular accumulation of cisplatin, but not of ZD0473, was observed in the PC-14/CDDP cells compared with the levels in PC-14 parental cells. The reduction in cisplatin accumulation is considered a major mechanism of the acquired cisplatin resistance in PC-14/CDDP cells. Therefore, the increase in platinum accumulation is considered a possible mechanism underlying the activity of ZD0473 in cisplatin-resistant cells. Glutathione-mediated resistance to cisplatin was also overcome by ZD0473 in PC-14/CDDP cells. In addition, we showed that the intraperitoneal administration of ZD0473 at its maximum tolerable dose in mice produced a marked in vivo antitumor activity against cisplatin-resistant PC-14/CDDP tumors. These results suggest that ZD0473 may be a potent agent in human lung cancer cells with multifactorial cisplatin resistance.

Antineoplastic Agents↗
PubMed1999

Evaluation of cross-resistance between responses to cisplatin, hyperthermia, and radiation in human glioma cells and eight clones selected for cisplatin resistance.

Human glioma cells were exposed to stepwise increasing concentrations of cisplatin and given a final, acute, high concentration treatment of cisplatin. From the surviving cells, eight cisplatin resistant clones were selected. These clones demonstrated a range of cisplatin sensitivities that were retained in the absence of cisplatin when cells were continually passaged. These cells were tested for cross-resistance to radiation and hyperthermia at 42 and 45 degrees C. The data showed that seven of the eight clones were also more radioresistant than the parental line, while one was more radiosensitive. The degree of cisplatin resistance was not related to the degree of radiation resistance. For hyperthermia at 42 and 45 degrees C, some of the clones were slightly more resistant than the parental line, while one clone was much more sensitive. This was not the same clone that was radiosensitive. In conclusion, there was no direct correlation between cisplatin resistance, radiation resistance, and hyperthermia response, although some of the clones were resistant to all three treatments.

Antineoplastic Agents↗
PubMed1992

Radiation sensitivities in various anticancer-drug-resistant human lung cancer cell lines and mechanism of radiation cross-resistance in a cisplatin-resistant cell line.

To determine whether there exists cross-resistance between anticancer drugs and radiation, six drug-resistant human lung cancer cell lines and their parental cell lines were examined for radiosensitivity using a growth-inhibition assay. Only one cisplatin-resistant cell line, PC-9/CDDP, showed cross-resistance to radiation. The other three cisplatin-resistant cell lines (PC-7/CDDP, PC-4/CDDP, and H69/CDDP), an etoposide-resistant cell line (H69/VP) and a camptothecin-resistant cell line (PC-7/CPT) did not show cross-resistance to radiation. To analyze the mechanism of radiation resistance in PC-9/CDDP cells, the formation and repair of radiation-induced DNA single-strand breaks (ssb) and double-strand breaks (dsb) were examined by alkaline elution and neutral elution respectively. Although the formation of DNA ssb and repair of both DNA ssb and DNA dsb were the same for both cell lines, the formation of DNA dsb in PC-9/CDDP cells was significantly less than those in PC-9 cells. Measurement of intracellular glutathione content in all of the cell lines revealed that only PC-9/CDDP cells had a significant increase of glutathione content compared to the parental cells. Buthionine sulfoximine treatment of PC-9/CDDP cells caused an increase of DNA dsb to the same levels as in PC-9 cells after irradiation and caused a complete radiosensitization. These results indicate that cross-resistance to radiation in drug-resistant cells in a rare phenomenon, and increased glutathione content may play a crucial role in the emergence of cross-resistance to radiation in the drug-resistant cells.

Antineoplastic Agents↗
PubMed2006

Intrinsic cisplatin resistance in lung and ovarian cancer cells propagating in medium acutely depleted of folate.

Many tumors develop intrinsic and/or acquired resistance to cisplatin. The purpose of the present study was to examine the influence of acute extracellular folate depletion prior to cisplatin treatment on the development of intrinsic cisplatin resistance. Lung and ovarian cancer cells were propagated in medium acutely depleted of folate and subsequently treated with cisplatin. The IC50 level for cisplatin, cell viability, cell proliferation, and global DNA methylation were determined. Gene expression profiling was performed using the Atlas Cancer 1.2 Array. Acute extracellular folate depletion resulted in the development of intrinsic cisplatin resistance. Cells propagating in medium acutely depleted of folate had a survival advantage compared to control cells when exposed to cisplatin, and thymidine supplementation did not reverse the intrinsic cisplatin resistance. cDNA microarray analysis revealed some novel genes associated with the development of intrinsic cisplatin resistance. Our report is the first to demonstrate that acute extracellular folate depletion results in intrinsic cisplatin resistance. If these results are confirmed by in vivo human studies, it would suggest that the folate status of the recipient of cisplatin might have an impact on response to that chemotherapeutic agent.

Antineoplastic Agents↗