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Picoplatin overcomes resistance to cell toxicity in small-cell lung cancer cells previously treated with cisplatin and carboplatin.

Tang CH, Parham C, Shocron E, McMahon G, Patel N - Cancer Chemother. Pharmacol. (2010)

Bottom Line: Cellular picoplatin accumulation in platinum-resistant and parental cells was high relative to levels of cellular platinum found in the same cell lines after cisplatin or carboplatin treatment.Our study demonstrates that picoplatin can overcome carboplatin and cisplatin resistance.The results suggest decreased platinum accumulation as a potential mechanism of platinum resistance in SCLC cells, provide candidate markers (e.g. several genes in the Hox, glutathione biosynthetic process, and MAGE families) that may serve as signatures for platinum resistance, support distinct effects of picoplatin on SCLC cells compared to other platinums, and provide a rationale to develop picoplatin for the treatment of recurrent SCLC following initial therapy with cisplatin or carboplatin.

View Article: PubMed Central - PubMed

Affiliation: Poniard Pharmaceuticals, Inc, South San Francisco, CA, USA. chi_hui.tang@yahoo.com

ABSTRACT

Purpose: Picoplatin is a new generation platinum designed to overcome platinum resistance. The goal of this study was to assess picoplatin anti-tumor activity and measure various cellular parameters in small-cell lung cancer (SCLC) cells resistant to cell killing by cisplatin and carboplatin.

Methods: We developed several platinum-resistant SCLC cell lines to evaluate picoplatin activity and drug resistance mechanisms in vitro. Drug cytotoxicity was measured by MTS assay. Total cellular platinum accumulation was measured by inductively coupled plasma mass spectrometry (ICP-MS). Whole genome gene expression profiling was carried out by microarray analysis.

Results: Picoplatin retained significant cytotoxic activity in platinum-resistant SCLC lines compared to cisplatin and carboplatin. Cellular picoplatin accumulation in platinum-resistant and parental cells was high relative to levels of cellular platinum found in the same cell lines after cisplatin or carboplatin treatment. Gene expression analyses revealed substantial differences in gene expression and highlighted specific annotation clusters in carboplatin-resistant cells. In addition, a similar gene expression pattern was observed in picoplatin-treated carboplatin-resistant and parental cells.

Conclusions: Our study demonstrates that picoplatin can overcome carboplatin and cisplatin resistance. The results suggest decreased platinum accumulation as a potential mechanism of platinum resistance in SCLC cells, provide candidate markers (e.g. several genes in the Hox, glutathione biosynthetic process, and MAGE families) that may serve as signatures for platinum resistance, support distinct effects of picoplatin on SCLC cells compared to other platinums, and provide a rationale to develop picoplatin for the treatment of recurrent SCLC following initial therapy with cisplatin or carboplatin.

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Total cellular platinum accumulation in parental and drug-resistant DMS53 cells. a Cellular platinum levels versus drug concentration. Attached cells were treated with drug (3, 10, and 30 μM) for 24 h, and lysates were harvested and analyzed by ICP-MS. Platinum levels were normalized to protein concentration for each sample. b Accumulation ratio is calculated by dividing the amount of platinum per mg of protein for the resistant cells by that of the parental cells. A ratio of one indicates that there is no difference in platinum accumulation between resistant and parental cells whereas a value of less than one represents reduced platinum accumulation in resistant cells. c Average accumulation ratio was obtained by averaging the ratios of the 3 concentrations tested for each drug. This was possible because the accumulation did not change over the drug concentration range used. Filled symbols = selection drug; Open symbols = picoplatin. CisR = cisplatin-resistant line; CarboR = carboplatin-resistant line. Data are the average of 3 independent experiments. Error bars represent the standard deviation for each data point. *p < 0.000025, Student’s t-test, two-tailed
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Fig2: Total cellular platinum accumulation in parental and drug-resistant DMS53 cells. a Cellular platinum levels versus drug concentration. Attached cells were treated with drug (3, 10, and 30 μM) for 24 h, and lysates were harvested and analyzed by ICP-MS. Platinum levels were normalized to protein concentration for each sample. b Accumulation ratio is calculated by dividing the amount of platinum per mg of protein for the resistant cells by that of the parental cells. A ratio of one indicates that there is no difference in platinum accumulation between resistant and parental cells whereas a value of less than one represents reduced platinum accumulation in resistant cells. c Average accumulation ratio was obtained by averaging the ratios of the 3 concentrations tested for each drug. This was possible because the accumulation did not change over the drug concentration range used. Filled symbols = selection drug; Open symbols = picoplatin. CisR = cisplatin-resistant line; CarboR = carboplatin-resistant line. Data are the average of 3 independent experiments. Error bars represent the standard deviation for each data point. *p < 0.000025, Student’s t-test, two-tailed

Mentions: Multiple drug influx and efflux mechanisms are known to regulate intracellular drug levels and in turn play a role in determining drug sensitivity [13]. Cellular drug accumulation is a major topic of study in resistance to platinum drugs. In order to ascertain whether cellular platinum accumulation varies between picoplatin and other platinum drugs, lysates from cells treated with drug were analyzed by ICP-MS for platinum. In all cases, platinum accumulation was essentially linear through the drug titration range for all drugs tested (Fig. 2a). In parental DMS53 cells, carboplatin treatment resulted in the lowest level of cellular platinum accumulation whereas picoplatin treatment resulted in the highest level. Platinum accumulation was not significantly different in parental DMS53 after treatment with cisplatin or picoplatin (P > 0.05). However, cisplatin-resistant DMS53 accumulated significantly less platinum after cisplatin treatment compared to picoplatin treatment (P < 0.0003). In both parental and carboplatin-resistant DMS53, picoplatin treatment resulted in strikingly higher cellular platinum levels than carboplatin treatment (P < 0.00005). Similar results were observed in DMS114 cells (Supplementary Fig. S1). Because platinum accumulation was linear over the treatment concentrations used, it was possible to express the data as an accumulation ratio, which is defined as the platinum accumulation in resistant cells divided by that of parental cells for each drug concentration. We found that this ratio was essentially constant over the concentration ranges tested, which is expected given the linear relationship between platinum accumulation and drug concentration (Fig. 2b). A number less than 1 indicates reduced drug accumulation in resistant cells relative to parental cells. Therefore, it was possible to calculate an average accumulation ratio (Fig. 2c), which represents the fraction of platinum accumulation in drug-resistant cells relative to its corresponding parental cells. Both cisplatin- and carboplatin-resistant DMS53 cells accumulated a lower level of their respective selection drug when compared with parental cells (62 and 52%, respectively; Fig. 2b), suggesting that influx/efflux mechanisms may be involved in drug resistance in these cells. Cisplatin-resistant DMS114 cells accumulated 71% of the selection drug relative to parental cells, whereas carboplatin-resistant DMS114 cells did not accumulate less selection drug (91%, Supplementary Fig. S1). Strikingly, platinum accumulation in cisplatin- and carboplatin-resistant DMS53 cells treated with picoplatin remained unchanged when compared with parental cells (104 and 99%, respectively, Fig. 2a–c). Together, these data suggest that the mechanisms involved in reducing platinum accumulation in cisplatin- and carboplatin-resistant SCLC cells do not affect platinum accumulation after picoplatin treatment.Fig. 2


Picoplatin overcomes resistance to cell toxicity in small-cell lung cancer cells previously treated with cisplatin and carboplatin.

Tang CH, Parham C, Shocron E, McMahon G, Patel N - Cancer Chemother. Pharmacol. (2010)

Total cellular platinum accumulation in parental and drug-resistant DMS53 cells. a Cellular platinum levels versus drug concentration. Attached cells were treated with drug (3, 10, and 30 μM) for 24 h, and lysates were harvested and analyzed by ICP-MS. Platinum levels were normalized to protein concentration for each sample. b Accumulation ratio is calculated by dividing the amount of platinum per mg of protein for the resistant cells by that of the parental cells. A ratio of one indicates that there is no difference in platinum accumulation between resistant and parental cells whereas a value of less than one represents reduced platinum accumulation in resistant cells. c Average accumulation ratio was obtained by averaging the ratios of the 3 concentrations tested for each drug. This was possible because the accumulation did not change over the drug concentration range used. Filled symbols = selection drug; Open symbols = picoplatin. CisR = cisplatin-resistant line; CarboR = carboplatin-resistant line. Data are the average of 3 independent experiments. Error bars represent the standard deviation for each data point. *p < 0.000025, Student’s t-test, two-tailed
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Fig2: Total cellular platinum accumulation in parental and drug-resistant DMS53 cells. a Cellular platinum levels versus drug concentration. Attached cells were treated with drug (3, 10, and 30 μM) for 24 h, and lysates were harvested and analyzed by ICP-MS. Platinum levels were normalized to protein concentration for each sample. b Accumulation ratio is calculated by dividing the amount of platinum per mg of protein for the resistant cells by that of the parental cells. A ratio of one indicates that there is no difference in platinum accumulation between resistant and parental cells whereas a value of less than one represents reduced platinum accumulation in resistant cells. c Average accumulation ratio was obtained by averaging the ratios of the 3 concentrations tested for each drug. This was possible because the accumulation did not change over the drug concentration range used. Filled symbols = selection drug; Open symbols = picoplatin. CisR = cisplatin-resistant line; CarboR = carboplatin-resistant line. Data are the average of 3 independent experiments. Error bars represent the standard deviation for each data point. *p < 0.000025, Student’s t-test, two-tailed
Mentions: Multiple drug influx and efflux mechanisms are known to regulate intracellular drug levels and in turn play a role in determining drug sensitivity [13]. Cellular drug accumulation is a major topic of study in resistance to platinum drugs. In order to ascertain whether cellular platinum accumulation varies between picoplatin and other platinum drugs, lysates from cells treated with drug were analyzed by ICP-MS for platinum. In all cases, platinum accumulation was essentially linear through the drug titration range for all drugs tested (Fig. 2a). In parental DMS53 cells, carboplatin treatment resulted in the lowest level of cellular platinum accumulation whereas picoplatin treatment resulted in the highest level. Platinum accumulation was not significantly different in parental DMS53 after treatment with cisplatin or picoplatin (P > 0.05). However, cisplatin-resistant DMS53 accumulated significantly less platinum after cisplatin treatment compared to picoplatin treatment (P < 0.0003). In both parental and carboplatin-resistant DMS53, picoplatin treatment resulted in strikingly higher cellular platinum levels than carboplatin treatment (P < 0.00005). Similar results were observed in DMS114 cells (Supplementary Fig. S1). Because platinum accumulation was linear over the treatment concentrations used, it was possible to express the data as an accumulation ratio, which is defined as the platinum accumulation in resistant cells divided by that of parental cells for each drug concentration. We found that this ratio was essentially constant over the concentration ranges tested, which is expected given the linear relationship between platinum accumulation and drug concentration (Fig. 2b). A number less than 1 indicates reduced drug accumulation in resistant cells relative to parental cells. Therefore, it was possible to calculate an average accumulation ratio (Fig. 2c), which represents the fraction of platinum accumulation in drug-resistant cells relative to its corresponding parental cells. Both cisplatin- and carboplatin-resistant DMS53 cells accumulated a lower level of their respective selection drug when compared with parental cells (62 and 52%, respectively; Fig. 2b), suggesting that influx/efflux mechanisms may be involved in drug resistance in these cells. Cisplatin-resistant DMS114 cells accumulated 71% of the selection drug relative to parental cells, whereas carboplatin-resistant DMS114 cells did not accumulate less selection drug (91%, Supplementary Fig. S1). Strikingly, platinum accumulation in cisplatin- and carboplatin-resistant DMS53 cells treated with picoplatin remained unchanged when compared with parental cells (104 and 99%, respectively, Fig. 2a–c). Together, these data suggest that the mechanisms involved in reducing platinum accumulation in cisplatin- and carboplatin-resistant SCLC cells do not affect platinum accumulation after picoplatin treatment.Fig. 2

Bottom Line: Cellular picoplatin accumulation in platinum-resistant and parental cells was high relative to levels of cellular platinum found in the same cell lines after cisplatin or carboplatin treatment.Our study demonstrates that picoplatin can overcome carboplatin and cisplatin resistance.The results suggest decreased platinum accumulation as a potential mechanism of platinum resistance in SCLC cells, provide candidate markers (e.g. several genes in the Hox, glutathione biosynthetic process, and MAGE families) that may serve as signatures for platinum resistance, support distinct effects of picoplatin on SCLC cells compared to other platinums, and provide a rationale to develop picoplatin for the treatment of recurrent SCLC following initial therapy with cisplatin or carboplatin.

View Article: PubMed Central - PubMed

Affiliation: Poniard Pharmaceuticals, Inc, South San Francisco, CA, USA. chi_hui.tang@yahoo.com

ABSTRACT

Purpose: Picoplatin is a new generation platinum designed to overcome platinum resistance. The goal of this study was to assess picoplatin anti-tumor activity and measure various cellular parameters in small-cell lung cancer (SCLC) cells resistant to cell killing by cisplatin and carboplatin.

Methods: We developed several platinum-resistant SCLC cell lines to evaluate picoplatin activity and drug resistance mechanisms in vitro. Drug cytotoxicity was measured by MTS assay. Total cellular platinum accumulation was measured by inductively coupled plasma mass spectrometry (ICP-MS). Whole genome gene expression profiling was carried out by microarray analysis.

Results: Picoplatin retained significant cytotoxic activity in platinum-resistant SCLC lines compared to cisplatin and carboplatin. Cellular picoplatin accumulation in platinum-resistant and parental cells was high relative to levels of cellular platinum found in the same cell lines after cisplatin or carboplatin treatment. Gene expression analyses revealed substantial differences in gene expression and highlighted specific annotation clusters in carboplatin-resistant cells. In addition, a similar gene expression pattern was observed in picoplatin-treated carboplatin-resistant and parental cells.

Conclusions: Our study demonstrates that picoplatin can overcome carboplatin and cisplatin resistance. The results suggest decreased platinum accumulation as a potential mechanism of platinum resistance in SCLC cells, provide candidate markers (e.g. several genes in the Hox, glutathione biosynthetic process, and MAGE families) that may serve as signatures for platinum resistance, support distinct effects of picoplatin on SCLC cells compared to other platinums, and provide a rationale to develop picoplatin for the treatment of recurrent SCLC following initial therapy with cisplatin or carboplatin.

Show MeSH
Related in: MedlinePlus