Mechanisms for cisplatin-FUra synergism and cisplatin resistance in human ovarian carcinoma cells both in vitro and in vivo

Platinum resistance in breast and ovarian cancer cell lines

Breast and ovarian cancers are among the 10 leading cancer types in females with mortalities of 15% and 6%, respectively. Despite tremendous efforts to conquer malignant diseases, the war on cancer declared by Richard Nixon four decades ago seems to be lost. Approximately 21,800 women in the US will be diagnosed with ovarian cancer in 2011. Therefore, its incidence is relatively low compared to breast cancer with 207.090 prognosed cases in 2011. However, overall survival unmasks ovarian cancer as the most deadly gynecological neoplasia. Platinum-based chemotherapy is emerging as an upcoming treatment modality especially in triple negative breast cancer. However, in ovarian cancer Platinum-complexes for a long time are established as first line treatment. Emergence of a resistant phenotype is a major hurdle in curative cancer therapy approaches and many scientists around the world are focussing on this issue. This review covers new findings in this field during the past decade.

Prognostic significance of numeric aberrations of genes for thymidylate synthase, thymidine phosphorylase and dihydrofolate reductase in colorectal cancer

BACKGROUND

Most human cancer cells have structural aberrations of chromosomal regions leading to loss or gain of gene specific alleles. This study aimed to assess the range of gene copies per nucleus of thymidylate synthase (TYMS), thymidine phosphorylase (TP) and dihydrofolate reductase (DHFR) in colorectal cancer, and to evaluate its prognostic significance following adjuvant chemotherapy, since these enzymes are closely related to efficacy of 5-fluorouracil (5FU).

PATIENTS AND METHODS

Consecutive patients (n = 314), who were completely resected for colorectal cancer stages II-IV and adjuvantly treated with 5-FU were retrospectively evaluated. Paraffin embedded tumor specimens were assessed for gene copies per nucleus of TYMS, TP and DHFR by fluorescence in situ hybridisation (FISH) using specific peptide nucleic acid probes. Outcome according to gene copies per nucleus above and below the median were compared. Also TYMS expression, assessed by immunohistochemistry, was associated with TYMS copies per nucleus.

RESULTS

The number of gene copies per nucleus were 1.7 (0.7-2.8), 1.8 (0.9-3.1) and 1.8 (1.1-2.7) median (range) for TYMS, TP and DHFR, respectively. TYMS expression was directly associated with TYMS genes per nucleus (p = 0.05). Cox multivariate analysis, adjusted for the prognostic impact of disease stage, vascular tumor invasion, and bowel obstruction at resection, revealed that high TYMS gene copy number was associated with significantly higher risk of recurrence (HR = 1.6; 95%CI 1.1-2.2; p = 0.02) and death (HR = 1.6; 95%CI 1.1-2.3; p = 0.01). No significant differences in outcome appeared according to TP and DHFR gene ratios.

CONCLUSION

Aberration of TYMS gene is of significance to expression of TYMS, which may influence the biology and 5-FU sensitivity of colorectal cancer. This may be utilized in the allocation of patients for treatment approaches and for decision on follow-up programs.

A pharmacokinetic interaction study of docetaxel and cisplatin plus or minus 5-fluorouracil in the treatment of patients with recurrent or metastatic solid tumors

BACKGROUND

The purpose of this study was to look at the pharmacokinetics of docetaxel, cisplatin-derived platinum and 5-fluorouracil (5-FU), when used in combination, to exclude potential clinically relevant pharmacokinetic interactions.

METHODS

Fifteen patients with recurrent or metastatic solid tumors were randomized to receive docetaxel 75 mg/m2 and cisplatin 75 mg/m2 in the first treatment course on day 1 and the same combination plus 5-FU 750 mg/m2/day on days 1-5 in the second course, or the two treatment courses in reversed order. Cycles were repeated every 3 weeks. A pharmacokinetic analysis was performed during the first two cycles.

RESULTS

Full pharmacokinetic data was available for 12 of the 15 patients. Treatment was tolerated well, with frequency of toxicity consistent with the safety profile known for docetaxel, cisplatin and 5-FU. Mean clearance values for docetaxel and cisplatin showed no statistically significant difference across the "triple" and the "double" combination treatments, and the mean pharmacokinetic parameters of all agents were within the ranges for previously reported single agent treatment.

CONCLUSION

No clinically relevant pharmacokinetic interactions between docetaxel, cisplatin and 5-FU used in combination were noticed in this study.

Cellular processing of platinum anticancer drugs

Cisplatin, carboplatin and oxaliplatin are platinum-based drugs that are widely used in cancer chemotherapy. Platinum-DNA adducts, which are formed following uptake of the drug into the nucleus of cells, activate several cellular processes that mediate the cytotoxicity of these platinum drugs. This review focuses on recently discovered cellular pathways that are activated in response to cisplatin, including those involved in regulating drug uptake, the signalling of DNA damage, cell-cycle checkpoints and arrest, DNA repair and cell death. Such knowledge of the cellular processing of cisplatin adducts with DNA provides valuable clues for the rational design of more efficient platinum-based drugs as well as the development of new therapeutic strategies.

Platinum-based chemotherapy in metastatic breast cancer: current status

Cisplatin and carboplatin are active in previously untreated patients with metastatic breast cancer (MBC) with mean response rates (RRs) of 50 and 32%, respectively. In pretreated patients the RR to cisplatin/carboplatin monotherapy declines markedly to <10%. Cisplatin and carboplatin have been combined with many other cytotoxics. In first-line setting high activity has been observed in combination with taxanes or vinorelbine (RRs consistently approximately 60%). It appears that these newer combinations are superior to older regimens with etoposide (RRs 30 to 50%) or 5-fluorouracil (RRs 40 to 60%). Cisplatin-/carboplatin-based regimens with infusional 5-FU and epirubicin/paclitaxel/vinorelbine achieve high RRs of around 60 to 80%. However these regimens are difficult to administer in all patients because they require central venous access for continuous 5-FU infusion. In pretreated MBC the combinations of cisplatin-taxane/vinorelbine/gemcitabine or carboplatin-docetaxel/vinorelbine yield RRs of 40 to 50%, which are higher than those achieved with platinum-etoposide/5-FU. In locally advanced disease cisplatin-based regimens achieve very high RRs (>80%). This would suggest that in chemotherapy-naïve patients platinum-based therapy might have an important role to play. Additionally the synergy demonstrated between platinum compounds, taxanes and herceptin, in preclinical and clinical studies is of immense importance and the results of the two ongoing Breast Cancer International Research Group randomized phase III studies are eagerly awaited. These studies may help clarify the role of platinum compounds in the treatment of metastatic and possibly early breast cancer.

Phase I trial of the antifolate ZD9331 in combination with cisplatin in patients with refractory solid malignancies

PURPOSE

To determine the maximum tolerated dose and dose-limiting toxicities (DLTs) of ZD9331 in combination with cisplatin in patients with refractory solid tumors and to describe any preliminary antitumor activity associated with this regimen.

MATERIALS AND METHODS

Patients received combination therapy with ZD9331 as a 30-min infusion on days 1 and 8 of a 21-day cycle at doses of 100 or 130 mg/m(2), followed by cisplatin at 50 or 75 mg/m(2) as a 30- to 60-min infusion on day 1 only.

RESULTS

A total of 16 patients received 59 cycles of ZD9331 and cisplatin. Patients were enrolled at three dose levels: ZD9331/cisplatin 100/50 ( n=3), 130/50 ( n=9), 130/75 ( n=4). DLTs at 130/75 included thrombocytopenia, neutropenia, fatigue, nausea, vomiting and stomatitis. Among 15 evaluable patients, 2 showed a partial response (patients with mesothelioma and head and neck cancer) and 6 showed stable disease (for a median of 5.5 cycles).

CONCLUSIONS

ZD9331 in combination with cisplatin was well tolerated at a dose of 130/50 mg/m(2) after establishing the principal DLTs of neutropenia and thrombocytopenia. The combination shows evidence of antitumor activity in a pretreated population.

Clinical significance of thymidylate synthase expression in bladder cancer

BACKGROUND

The purpose of the present paper was to investigate the clinical significance of thymidylate synthase (TS) expression in bladder cancer and its association with proliferation markers, such as p53, Ki-67, and proliferating cell nuclear antigen (PCNA).

METHODS

Thymidylate synthase gene expression in 54 patients with bladder cancer was measured by the reverse transcription polymerase chain reaction (RT-PCR) method using glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as an internal standard. The TS expression was also examined immunohistochemically. Immunohistochemical studies of p53, Ki-67, and PCNA expression were carried out to examine the correlation between TS expression and the expression of proliferation markers in the tumors. Prognostic and clinical outcome factors such as vascular invasion and distant metastasis were also examined along with TS expression.

RESULTS

Twenty-four patients with invasive bladder cancer had TS levels of 5.07 +/- 0.77 (mean +/- SE), while 30 patients with superficial bladder cancer had TS levels of 2.28 +/- 0.38. There was a significant difference in TS levels between invasive and superficial bladder cancer (P = 0.001). There was a positive correlation between TS expression and each proliferation marker of p53 (r = 0.686, P < 0.01), Ki-67 (r = 0.715, P < 0.0001) or PCNA expressions (r = 0.670, P < 0.0001) in these patients. Patients with high TS levels (TS > or = 2.63, the median value) had significantly higher rates of vascular invasion and distant metastasis. Kaplan-Meier analysis demonstrated that patients with high TS levels (TS > or = 2.63) had unfavorable prognosis compared to patients with low TS levels (TS < 2.63; P = 0.034). Furthermore, patients with high TS staining had a significantly poorer prognosis than those with low staining (P = 0.012).

CONCLUSION

Determination of level of TS expression may help in the selection of an appropriate treatment for bladder cancer because TS expression influences the biological characteristic of bladder tumor.

Mechanisms of resistance to cisplatin

The use of cisplatin in cancer chemotherapy is limited by acquired or intrinsic resistance of cells to the drug. Cisplatin enters the cells and its chloride ligands are replaced by water, forming aquated species that react with nucleophilic sites in cellular macromolecules. The presence of the cisplatin adducts in DNA is thought to trigger cell cycle arrest and apoptosis. Knowledge of the mechanism of action of cisplatin has improved our understanding of resistance. Decreased intracellular concentration due to decreased drug uptake, increased reflux or increased inactivation by sulfhydryl molecules such as glutathione can cause resistance to cisplatin. Increased excision of the adducts from DNA by repair pathways or increased lesion bypass can also result in resistance. Finally, altered expression of regulatory proteins involved in signal transduction pathways that control the apoptotic pathway can also affect sensitivity to the drug. An improved understanding of the mechanisms of resistance operative in vivo has identified targets for intervention and may increase the utility of cisplatin for the treatment of cancer.

Use of hydroxyurea to alter drug resistance of human tumor cells

Tumor cell resistance to cancer chemotherapeutic agents is a well-recognized problem for clinicians. Efforts are being made to develop agents that are not affected by cross-resistance to other drugs, as observed with the mdr phenotype. Other efforts are focused on reversing drug resistance to enhance chemotherapeutic intervention. Gene amplification accounts for one mechanism through which tumor cells develop drug resistance. Since amplified genes may be unstable, the elimination of these genes is likely to be a promising new target for cancer chemotherapy. The use of HU at low concentrations either to reestablish tumor sensitivity to chemotherapeutic agents or to decrease tumorigenicity, accomplished by the reduction of oncogene copy number, continues to be investigated. Studies thus far all report similar effects of noncytotoxic concentrations of HU on unstably amplified genes (EC DNA elimination), regardless of what gene is harbored on the EC DNA. The next essential step in the evaluation of HU-induced EC DNA elimination is to study the phenomena in vivo. In spite of extensive tissue distribution, HU appears to have pharmacokinetic properties, due to its short half-life, that may limit investigators' ability to study its use in prototype animal tumor models such as the nude mouse. In contrast, HU's half-life in humans (3.5 to 4.5 hours) [122] is comparatively longer, and therefore clinical trials may prove less troublesome.

Chemotherapeutic drug resistance in the management of head and neck cancer

Considerable progress has been made in the development of more effective chemotherapy regimens for squamous cell head and neck carcinomas. Unfortunately, increased response rates have not been translated into marked improvements in survival since durations of response have been brief, and the natural history of the disease has ultimately remained unaltered. Since the development of drug resistance is a major obstacle to successful antineoplastic chemotherapy, comprehensive efforts have been focused on understanding the underlying mechanisms. In this review, general and specific aspects of drug resistance related to head and neck cancer are addressed. In particular, mechanisms of resistance towards the most widely used antineoplastic drugs in head and neck malignancies--methotrexate, cisplatin, 5-fluorouracil, bleomycin, and vincristine--are discussed.

Cisplatin resistance in human cancers

Cancer chemotherapeutic agents primarily act by damaging cellular DNA directly or indirectly. Tumor cells, in contrast to normal cells, respond to cisplatin with transient gene expression to protect and/or repair their chromosomes. Repeated cisplatin treatments results in a stable resistant cell line with enhanced gene expression but lacking gene amplification for the proteins that will limit cisplatin cytotoxicity. Recently, several new human cell lines have been characterized for cisplatin resistance. These cell lines have led to a better understanding of the molecular and biochemical basis of cisplatin resistance. The c-fos proto-oncogene, a master switch for turning on other genes in response to a wide range of stimuli, has been shown to play an important role in cisplatin resistance both in vitro and in patients. Based on these studies, new strategies have been developed to circumvent and/or exploit clinical cisplatin resistance.

Utility of the polymerase chain reaction in detection of gene expression in drug-resistant human tumors

Recently, an enzymatic amplification method, the polymerase chain reaction (PCR), was modified to amplify a sequence of a drug resistance gene. The PCR assay can confirm data achieved by conventional molecular biology techniques, while requiring less time and fewer patient cells. It can be quantitated for gene expression. The data generated make it possible to analyze m-RNA expression in tumor samples without being limited to detecting only gene amplification in response to cancer chemotherapy. The PCR assay can be an effective device in the early detection of resistance to chemotherapy.