Addition of verapamil and tamoxifen to the initial chemotherapy of small cell lung cancer. A phase I/II study

Expression of estrogen and progesterone receptors across human malignancies: new therapeutic opportunities

Estrogen and progesterone receptors (ERs and PRs) are known for their prognostic as well as treatment predictive value in breast cancer. Although these receptors are differentially expressed in some other malignancies, and likely participate in the biology of those cancer types, the relevance to outcome and therapy is not well established. The use of ER as a highly effective therapeutic target in oncology was pioneered in breast cancer, and the lessons learned from its success could potentially benefit patients with several other malignancies in which hormone receptors are highly expressed. Indeed, there are several potent drugs available that target hormone receptors. These agents show incontrovertible evidence of benefit in patients with hormone receptor-positive breast cancer. It is conceivable that these drugs may have salutary effects in a variety of cancers other than those originating in the breast, based on the overexpression of hormone receptors in some patients, and the preclinical and clinical reports showing responses to these drugs in diverse cancers, albeit in small series or anecdotally. We therefore undertook a literature review in order to summarize the current data regarding the biologic and clinical implications of expression of estrogen and progesterone receptors in various malignancies and the possibilities for deployment of hormone manipulation beyond breast cancer.

Immunization with liposome-anchored pegylated peptides modulates doxorubicin sensitivity in P-glycoprotein-expressing P388 cells

The clinical use of chemotherapy in cancer treatment is limited by the occurrence of multidrug resistance (MDR) associated with the overexpression of membrane transporters, one of the best known is P-glycoprotein (Pgp), that actively expels drugs out of tumor cells. To overcome Pgp-mediated MDR, synthetic peptides corresponding to fragments from extracellular loops 1, 2 and 4 of the murine Pgp were coupled to polyethylene glycol-distearoylphosphatidylethanolamine and inserted into empty or monophosphoryl lipid A-containing liposomes. This formulation elicited specific antibodies which blocked Pgp-mediated efflux of doxorubicin, resulting in increased intracellular drug accumulation and subsequent potentiation of the cytotoxic effect of doxorubicin on multidrug-resistant P388 (P388R) cells. Previous immunizations with MDR1 peptides improved the efficiency of chemotherapy against P388R cells in vivo, with an increase of 83% of mice survival time. Overall, these results suggest that this approach can modulate Pgp activity by blocking drug efflux and may have clinical relevance as an alternative strategy to toxic chemosensitizers in drug-resistant cancer therapy.

Induction of autoantibodies to murine P-glycoprotein: Consequences on drug sensitivity in MDR cancer cells and on the expression of mdr genes in organs

Overexpression of the 170 kDa plasma membrane P-glycoprotein (P-gp) represents the most common MDR mechanism in chemotherapy. In this work, specific autoantibodies to fragments from extracellular loops 1, 2, and 4 of the murine MDR1 P-gp were elicited in mice using synthetic palmitoylated peptides reconstituted in liposomes and alum. The highest IgG level was observed after the third immunization and the immune response against lipopeptides was still detected more than 200 days after immunizations. Immunocytochemichal studies revealed that these antibodies were specific for P-gp. When incubated with P-gp-expressing MDR cell lines, serum from immunized mice restored sensitivity to either doxorubicin or vinblastine, or had no effect in a cell type specific manner, suggesting that several mechanisms may occur in the establishment of the MDR phenotype. The expression of mdr1 and mdr3 genes was unchanged in organs from mice immunized with palmitoylpeptides grafted on liposomes. These results suggest that the induction of autoantibodies to P-gp is a safe strategy to overcome MDR in cancer chemotherapy.

Immunothérapie anti-tumorale contre la multidrogue résistance

Overexpression of a membrane glycoprotein (P170) represents the most common multidrug resistance (MDR) mechanism in cancer therapy. Specific autoantibodies to extracellular loops 1, 2 and 4 of murine P170 are elicited in mice using palmitoylated synthetic peptides reconstituted in liposomes with or without Lipid A and resuspended in alum. IgM antibodies are detected 14 days following the first injection and IgG1 become predominant after the third challenge. Animals do not show any autoimmunity symptoms or induced toxicity up to 18 months after the immunization. Previous immunizations of mice using liposomes with mdr1 peptides efficiently improve chemotherapy with doxorubicin and vinblastine against P388 R cells with a 77% increase of survival half time in the immunized group. Sera from immunized mice are also effective in reducing cellular resistance to vinblastine and doxorubicin in vitro. Taken together these data suggest that this immunization approach might have potential clinical applications.

Inhibition of multidrug resistance by immunisation with synthetic P-glycoprotein-derived peptides

Overexpression of the membrane glycoprotein (P170) represents the most common multidrug resistance (MDR) mechanism in cancer therapy. Specific auto-antibodies to extracellular loops 1, 2 and 4 of murine P170 were elicited in mice using palmitoylated synthetic peptides reconstituted in liposomes, with or without Lipid A, and resuspended in alum. IgM antibodies were detected 14 days following the first injection and IgG1 became predominant after the third challenge. Animals did not show any auto-immune symptoms or induced toxicity up to 18 months after the immunisation. Previous immunisations of mice using liposomes with MDR1 peptides increases the efficacy of chemotherapy treatments with doxorubicin and vinblastine against P388 R cells with increase of 77% in the survival half time in the immunised group. Sera from the immunised mice were also effective in reducing cellular resistance to vinblastine and doxorubicin in vitro. Taken together, these data suggest that this immunisation approach might have potential clinical applications.

Adding high-dose tamoxifen to CHOP does not influence response or survival in aggressive non-Hodgkin's lymphoma: an interim analysis of a randomized phase III trial

PURPOSE

CHOP is the standard regimen currently used in the management of the majority of patients with aggressive non-Hodgkin's lymphoma (NHL). However, CHOP only produces 30-35% long-term survival. We hypothesized that adding high-dose tamoxifen, which is known to have multiple drug resistance-modulatory effects, to the CHOP regimen could increase the response rate, and consequently enhance the survival of patients with NHL.

PATIENTS AND METHODS

In a prospective, controlled, and randomized study, eligible adult patients with aggressive NHL were randomized between CHOP only (Group I), or CHOP plus high-dose tamoxifen (Group II). The primary aim was to assess the effect of tamoxifen on complete response (CR) rate, with the secondary evaluation of tamoxifen potential impact on survival. The interim analysis of this study is presented.

RESULTS

Fifty-one and forty-seven evaluable patients were randomized to Group I and Group II, respectively. The median age of all patients was 53 y (range 18-78 y). The two groups had comparable distributions of the pretreatment prognostic variables. The CR for patients in Group I was 80% (41 patients) as compared with 74% (35 patients) in Group II (P=0.48). Likewise, there was no apparent difference in the partial remission rates between the two groups (6% vs 15%, respectively). Of patients who initially attained CR, 15 (37%) and 10 (29%) subsequently relapsed in Groups II and I respectively (P = 0.45). The NHL International Prognostic Index (IPI) was the only factor that predicted attaining CR. At the time of this interim analysis, the actuarial-estimated overall survival (OS) probability (+/-S.E.) for the entire population at 5 y was 58% (+/-6) with no survival difference between the two groups (P=0.51). Only attaining CR and the IPI predicted OS probability. The probability of remaining event-free at 5 y (+/-SE) for those achieving CR was 72% (+/-9), and there was no significant difference between the two treatment groups (P=0.68). Toxicity profile was similar in the two groups.

CONCLUSION

Based on this interim analysis, combining high-dose tamoxifen, as used in this study, with the CHOP regimen has failed to have any favorable effect on the outcome of patients with aggressive NHL, and therefore cannot be recommended for future trials.

Chemotherapy for brain metastases of lung cancer: a review

In lung cancer patients brain metastases develop with a high frequency. For years radiotherapy has been the standard treatment for these patients. Here we review the experience with chemotherapy for brain metastases in lung cancer patients. The concept of the brain as pharmacological sanctuary site when brain metastases are present is challenged and it is argued that chemotherapy does play a role in this situation. Recent clinical trials indicate that the combination of chemotherapy and radiotherapy may become the standard treatment for lung cancer patients with brain metastases. It is unclear whether for micrometastatic disease to the brain, blood brain barrier function is of importance for the outcome of chemotherapy in lung cancer patients with respect to the development of overt brain metastases. Areas of improvement of delivery of cytotoxic agents to the brain when brain metastases have not yet developed are discussed.

Treatment of advanced colorectal cancer with doxorubicin combined with two potential multidrug-resistance-reversing agents: high-dose oral tamoxifen and dexverapamil

On the basis of the overexpression of the MDR1 gene in human colorectal cancer, which may constitute a molecular basis for intrinsic drug resistance that can be reversed, and because of the limited therapeutic value of conventional cytotoxic treatment in this common disease, the present phase II study of P-glycoprotein-directed double modulation was initiated. Fifteen patients with measurable metastatic colorectal cancer, all of whom were refractory to first-line chemotherapy with 5-fluorouracil/leukovorin, were entered in this trial. Treatment consisted of 80 mg tamoxifen twice daily on days 1-9, oral dexverapamil every day on days 7-9, and 60 mg/m2 doxorubicin given by intravenous bolus injection on day 8. Courses were repeated every 4 weeks. After a median of three (between one and six) courses, none of the 14 evaluable patients had objective response, and 4 had stable disease. Adverse reactions consisted mainly of myelosuppression (WHO grade IV granulocytopenia was noted in 40%), and mild and reversible dexverapamil-related cardiovascular side-effects, specifically hypotension (47%). Our results suggest that, despite the histological demonstration of high levels of P-glycoprotein in colorectal cancer and administration of two potentially synergistic chemosensitizers, we were unsuccessful in circumventing its primary resistance to chemotherapy.

The chemosensitizer cyclosporin A enhances the toxic side-effects of doxorubicin in the rat

The feasibility of using chemosensitizers in the circumvention of P-glycoprotein-mediated multidrug resistance has been shown in many studies. We recently reported on the chemosensitizing effect of cyclosporin A (CsA) on doxorubicin in a rat solid tumour model. Using the same experimental design we investigated the side-effects of the combination treatment. During the 35-day experiment doxorubicin treatment caused dose-dependent weight loss, which was enhanced by combination treatment with CsA. The main doxorubicin-related side-effects were myelosuppression (transient leucopenia and thrombopenia) and nephrotoxicity. Damage to the kidney was severe, leading to a nephrotic syndrome and resulting in ascites, pleural effusion, hypercholesterolaemia and hypertriglyceridaemia. These toxicities were enhanced by the addition of the chemosensitizer CsA. Mild doxorubicin-related cardiomyopathy and minimal hepatotoxicity were seen on histological examination. There were no signs of enhanced toxicity of the combination treatment in tissues with known high expression levels of P-glycoprotein, like the liver, adrenal gland and large intestine. CsA had a low toxicity profile, as it only caused a transient rise in bilirubin. In conclusion, the chemosensitizer CsA enhanced the side-effects of the anticancer drug doxorubicin without altering the toxicity pattern. There was no evidence of a therapeutic gain by adding CsA to doxorubicin, compared to single-agent treatment with doxorubicin in 25%-33% higher doses, because of the enhanced toxicity of the combination treatment.

Modulation of doxorubicin-toxicity by tamoxifen in multidrug-resistant tumor cells in vitro and in vivo

Modulation of the resistance of tumors offers new strategies to improve the therapeutical treatment of cancer. In this report, the anti-oestrogen tamoxifen was investigated in multidrug-resistant tumor cells in vitro and in vivo. The doxorubicin-resistance of L 1210/DOX-tumor cells, which express the multidrug-resistance phenotype, could be completely circumvented by addition of 1 microgram/ml tamoxifen. In contrast, no increased effect could be observed in the parental L 1210 tumor cells or in cytosine arabinoside-resistant L 1210 cells not expressing the multidrug-resistance phenotype. Thus, the enhancing effect of tamoxifen was restricted only to the multidrug-resistant L 1210/DOX tumor cells. Similar to the in vitro experiments, a significant reduction in the growth in solid tumors of mice by the combined treatment of doxorubicin and tamoxifen was again observed only in the multidrug-resistant L 1210/DOX tumors.

Clinical trials of agents that reverse multidrug resistance. A literature review

BACKGROUND

The discovery of the P-170 glycoprotein as a mediator of multidrug resistance (MDR) represents one of the most important research accomplishments in antineoplastic pharmacology during the last decade. Demonstration of P-170 in epithelial tissues, untreated and chemotherapeutically pretreated human malignancies, and identification of various agents capable of reversing resistance in vitro generated enthusiasm for clinical studies throughout the world. The authors provide an overview of the current status of clinical investigations of MDR1 reversing agents in hematologic and solid malignancies.

METHODS

The authors performed an extensive literature search and selected more than 70 articles concerning the potential clinical relevance of P-glycoprotein/MDR1 modulating agents. Information abstracted included type of reverting agent and chemotherapeutic regimen, number of patients, tumor type, histologic proof of P-glycoprotein expression, and objective response rates.

RESULTS

Proof of the involvement of MDR1 in clinical drug resistance has been slow to accumulate, primarily because of difficulties in adapting assays of MDR1 expression and in planning appropriate trials. Pilot studies have shown that verapamil, cyclosporine, and other chemosensitizers may reverse resistance in a subset of patients, but significant (cardiovascular) side effects are common. For leukemias, lymphomas, and multiple myeloma, response rates of 60-80% may be achieved with the potential for cure, whereas in solid tumors, only a few patients appear to benefit.

CONCLUSIONS

Because of predominantly negative results and unanswered fundamental questions regarding the biology of P-glycoprotein, additional clinical trials with less toxic modulators or their combination are appropriate to delineate optimal strategies for MDR1 reversal and to define the spectrum of responsive tumors. Additional attention also must be given to the coexistence of other resistance mechanisms that may offer separate opportunities for modulation.

A randomised clinical study of verapamil in addition to combination chemotherapy in small cell lung cancer. West of Scotland Lung Cancer Research Group, and the Aberdeen Oncology Group

Proliferation of drug resistant tumour following chemotherapy is the principal cause of treatment failure in small cell lung cancer (SCLC). Verapamil has been shown to partially restore drug sensitivity in tumour cells rendered resistant in vitro. The results of the first large-scale randomised study of a resistance modifying drug given in conjunction with chemotherapy in cancer patients are reported. Two hundred and twenty-six patients have been entered. All patients received four cycles of cyclophosphamide (750 mg m-2), doxorubicin (40 mg m-2) and vincristine (1.4 mg m-2) on Day 1 and etoposide (75 mg m-2) on Days 1, 2 and 3, repeated at 21 day intervals. Those patients randomised to the verapamil arm received oral verapamil 120 mg qid for 5 days with each course of chemotherapy. Similar numbers of cycles of protocol treatment were given in both arms with over 75% of patients completing all four cycles. There were no significant differences in general toxicities between the two arms, except for more severe alopecia in the verapamil treatment group (P = 0.045). There was no significant difference in cardiovascular or haematological toxicity, although the median nadir white cell count after Cycle 1 chemotherapy was lower in the verapamil arm (P = 0.065) and there were significantly more dose reductions after Cycle 1 in the verapamil arm (P = 0.031). No statistically significant differences in response (P = 0.582) or survival (P = 0.290) data were seen. The absence of a significant improvement in response or survival using verapamil may relate to the low blood levels of verapamil seen in the clinic (0.8 microM), in contrast to those known to be maximally active in vitro (> 6 microM) or to the presence of other cellular mechanisms by which drug resistance develops.

Increased chemosensitivity to doxorubicin of intrinsically multidrug-resistant human colon carcinoma cells by prolonged exposure to verapamil

Resistance modifying agents (RMA) such as verapamil (VER) have proved effective in reversing multidrug resistance (MDR) in many in vitro experimental models, but clinical results with RMA have been disappointing. To clarify this apparent discrepancy we have evaluated the cytotoxic effects of doxorubicin (DOX) plus VER in four human colon carcinoma (HCOC) cell lines (LoVo, DLD-1, SW948, SW1116). These lines were selected on the basis of their levels of mdr1 mRNA being similar to those expressed by HCC obtained from non-drug-treated patients. In all cell lines the sensitising effect of VER on DOX cytotoxicity was schedule-dependent and maximal potentiation of DOX cytotoxicity was obtained by exposure to VER for a time > or = the cells' population doubling time.

Prochlorperazine as a doxorubicin-efflux blocker: phase I clinical and pharmacokinetics studies

Doxorubicin (DOX) efflux in drug-resistant cells is blocked by phenothiazines such as trifluoperazine (TFP) and prochlorperazine (PCZ) in vitro. The present phase I study was conducted in 13 patients with advanced, incurable, nonhematologic tumors to determine whether PCZ plasma levels high enough to block DOX efflux could be achieved in vivo. The treatment schedule consisted of prehydration and i.v. administration of 15, 30, 50, and 75 mg/m2 PCZ followed by a standard dose of 60 mg/m2 DOX. The hematologic toxicities attributable to DOX were as expected and independent of the PCZ dose used. Toxicities attributable to PCZ were sedation, dryness of the mouth, cramps, chills, and restlessness. The maximal tolerated dose (MTD) of PCZ in this schedule was 75 mg/m2. Pharmacokinetic analysis indicated a large interpatient variation in peak plasma PCZ levels that ranged from 95 to 1100 ng/ml. The three plasma half-lives of PCZ were: t1/2 alpha (+/- SE), 20.9 +/- 5.3 min; t1/2 beta, 1.8 +/- 0.3 h; and t1/2 gamma, 21.9 +/- 5.3 h. The volume of distribution (Vd), total clearance (ClT), and area under the curve (AUC) for PCZ were 2254 +/- 886 l/m2, 60.2 +/- 13.5 l m-2 h-1, and 1624 +/- 686 ng ml-1 h, respectively. DOX retention in tumor cells retrieved from patients during the course of therapy indicated the appearance of cells with enhanced DOX retention. The combination of DOX and high-dose i.v. PCZ appeared to be safe, well tolerated, and active in non-small-cell lung carcinoma.

Pharmacologic circumvention of multidrug resistance

The ability of malignant cells to develop resistance to chemotherapeutic drugs is a major obstacle to the successful treatment of clinical tumors. The phenomenon multidrug resistance (MDR) in cancer cells results in cross-resistance to a broad range of structurally diverse antineoplastic agents, due to outward efflux of cytotoxic substrates by the mdr1 gene product, P-glycoprotein (P-gp). Numerous pharmacologic agents have been identified which inhibit the efflux pump and modulate MDR. The biochemical, cellular and clinical pharmacology of agents used to circumvent MDR is analyzed in terms of their mechanism of action and potential clinical utility. MDR antagonists, termed chemosensitizers, may be grouped into several classes, and include calcium channel blockers, calmodulin antagonists, anthracycline and Vinca alkaloid analogs, cyclosporines, dipyridamole, and other hydrophobic, cationic compounds. Structural features important for chemosensitizer activity have been identified, and a model for the interaction of these drugs with P-gp is proposed. Other possible cellular targets for the reversal of MDR are also discussed, such as protein kinase C. Strategies for the clinical modulation of MDR and trials combining chemosensitizers with chemotherapeutic drugs in humans are reviewed. Several novel approaches for the modulation of MDR are examined.

Intermittent high-dose tamoxifen as a potential modifier of multidrug resistance

In vitro tamoxifen reverses multidrug resistance (MDR). To evaluate the clinical potential of using tamoxifen in this way, intermittent high-dose tamoxifen was combined with oral etoposide in 86 patients. At 320 mg/day tamoxifen for 6 days, mean plasma levels of tamoxifen in 11 patients increased from 453 ng/ml (range 269-664) on day 2 to 984 ng/ml (578-1336) on day 6. Of 31 patients who had plasma tamoxifen measured during the time of etoposide administration (days 4-6), 13(43%) were over 1111 ng/ml (3 mumol/l), an active in vitro level. Potentially active levels of the principal metabolite, N-desmethyl tamoxifen, were also obtained but accumulation was slower. Emesis and thromboembolism were toxicities. Tamoxifen is a modifier of MDR, a role that warrants further clinical studies.

A phase II study of epidoxorubicin in colorectal cancer and the use of cyclosporin-A in an attempt to reverse multidrug resistance

We determined the ability of the multidrug resistance (MDR) reversal agent cyclosporin-A to increase anthracycline drug accumulation in colorectal tumour cells in vitro, using the technique of on-line flow cytometry. Data of four previously untreated patients showed that cyclosporin-A can increase intracellular net-uptake of daunorubicin. A phase II study was initiated in 24 colorectal cancer patients. They received cyclosporin-A at a dose of 3 mg kg-1 over 1 h as i.v. infusion, at 7 h and at 1 h preceding cytotoxic drug administration. At the end of the second cyclosporin-A administration epidoxorubicin 90 mg m-2 was administered as i.v. bolus. Cycles were repeated every 3 weeks. Median cyclosporin-A peak blood levels and levels at 18 h after cytotoxic drug administration appeared to be 6248 ng ml-1 and 1012 ng ml-1 respectively. Only one partial response was observed, despite these high cyclosporin-A levels. Cyclosporin-A did not cause major toxicity, only a 29% incidence of hot flushes was observed. Epidoxorubicin toxicities were as expected but the frequency of severe leucocytopenia was striking. This treatment schedule can not be considered active in colorectal cancer.