Cancer in mice: effects of prednisolone or mepacrine alone and with cytotoxic drugs

Critical Review of Preclinical Approaches to Evaluate the Potential of Immunosuppressive Drugs to Influence Human Neoplasia

Many immunosuppressive drugs are associated with an increased risk of B-cell lymphoma, squamous cell carcinoma, and Kaposi sarcoma. Thirteen immunosuppressive drugs have been tested in 2-year carcinogenicity studies (abatacept; azathioprine; busulfan; cyclophosphamide; cyclosporine; dexamethasone; everolimus; leflunomide; methotrexate; mycophenolate mofetil; prednisone; sirolimus; and tacrolimus) and in additional models including neonatal and genetically modified mice; chemical, viral, ultraviolet, and ionizing radiation co-carcinogenesis, and in models with transplanted tumor cells. The purpose of this review is to outline the mechanisms by which immunosuppressive drugs can influence neoplasia, to summarize the available preclinical data on the 13 drugs, and to critically review the performance of the models. A combination of primary tumor and metastasis assays conducted with transplanted cells may provide the highest value for hazard identification and can be applied on a case-by-case basis. However, for both small molecules and therapeutic proteins, determining the relative risk to patients from preclinical data remains problematic. Classifying immunosuppressive drugs based on their mechanism of action and hazard identification from preclinical studies and a prospective pharmacovigilance program to monitor carcinogenic risk may be a feasible way to manage patient safety during the clinical development program and postmarketing.

Therapy of glioblastoma multiforme improved by the antimutagenic chloroquine

Object

Therapy of malignant tumors is frequently curtailed by the emergence of chemoresistant cell clones. Experimentally, the authors have demonstrated that chemotherapy for glioma in rats is markedly improved by the administration of the antimutagenic quinacrine. They studied the effects of chloroquine, an antimutagenic with an optimal pharmacological profile for human use, as adjuvant for the treatment of patients with glioblastoma multiforme (GBM).

Methods

In a prospective controlled randomized trial, 18 patients with GBM underwent standard treatment with surgery, chemotherapy, and radiotherapy; nine received an additional 150-mg dose of chloroquine daily starting 1 day after surgery and continued through the observation period. Nine matched patients were included as controls. Neuroimaging studies and clinical response were periodically compared. The follow-up period ranged from 24 to 50 months.

Survival time was defined as the main outcome measure. Survival was significantly longer in chloroquine-treated patients than in controls (33 ± 5 and 11 ± 2 months, respectively [p < 0.0002]). At the end of the observation period, four patients (46%) treated with chloroquine were alive, two had evidence of tumor remission after 2 years; in another two, tumor recurrence developed after 2 and 4 years of remission, respectively. No control patient survived more than 22 months after surgery.

Conclusions

Chronic administration of chloroquine greatly enhanced the response of GBM to antineoplastic treatment. Because the cytotoxicity of chloroquine on malignant cells is negligible, these favorable results appear mediated by its strong antimutagenic effect that precludes the appearance of resistant clones during radiotherapy and chemotherapy.

Quinacrine enhances carmustine therapy of experimental rat glioma

OBJECTIVE

The high rate of mutagenesis in malignant cells has been considered to be a primary factor in the appearance of chemotherapy-resistant cell clones in glioblastomas. Quinacrine binds strongly to deoxyribonucleic acid, preventing mutagenesis. We investigated whether quinacrine could improve carmustine therapy in C6 cell cultures and in C6 malignant gliomas implanted subcutaneously into Wistar rats.

METHODS

A potential chemopreventive effect of quinacrine on acquired resistance to carmustine therapy was studied in vitro and in vivo. Deoxyribonucleic acid damage was measured in cultured C6 cells by using the micronucleus test. Wistar rats with subcutaneously implanted C6 gliomas were treated with carmustine, quinacrine, or carmustine plus quinacrine, using pharmacological schemes similar to those used for human patients.

RESULTS

The addition of quinacrine to cultured C6 cells did not modify carmustine-induced cytotoxicity; however, the deoxyribonucleic acid damage in surviving cells was minor, as indicated by the frequency of micronucleated cells. The surviving cells continued to be susceptible to a second exposure to carmustine, in contrast to non-quinacrine-treated control cells, which developed resistance to carmustine in a subsequent exposure (P < 0.05). The rate of tumor remission was higher for glioma-bearing rats treated with quinacrine plus carmustine, compared with rats treated with carmustine alone (P < 0.01).

CONCLUSION

The addition of quinacrine to carmustine therapy increases the antineoplastic effect of the carmustine therapy. Our results suggest that chemical inhibition of mutagenesis in malignant glial cells during chemotherapy prevents the appearance of resistant clones.

Could an aminoacridine interfere with the cellular mechanisms involved in the process of human immunodeficiency virus infection?

Immune activation and synthesis of nucleic acids participate in the course of infection by human immunodeficiency virus. Aminoacridines, formally used as antiparasitic drugs, but almost abandoned nowadays for therapeutic use, are strong deoxyribonucleic acid chemoprotectors and lysosome stabilizers. Theoretically, these actions within the cell and other peculiar pharmacological characteristics of aminoacridines, particularly quinacrine, could pose barriers to human immunodeficiency virus infection and replication.

The effect of nifedipine alone or combined with cytotoxic chemotherapy on the mouse NC carcinoma in-vitro and in-vivo

Effects of the calcium antagonist nifedipine on the response of the murine NC carcinoma has been examined alone and together with cytotoxic chemotherapy in-vitro and in-vivo. The cytotoxic drug combination of methotrexate and melphalan, or nifedipine alone (0.2-25 micrograms mL-1), caused a concentration-related reduction of NC cell growth in culture. At the lower concentrations, combination to the cytotoxic drugs with nifedipine resulted in an addition of the separate drug effects, but with drug concentrations that on their own approached maximal effectiveness the combined response was less than additive. NC tumours were excised from mice 14 days after inoculation s.c. with NC cells, weighed, and extracted for prostanoids. Mouse survival was determined up to day 121, and cancer spread was recorded postmortem. Nifedipine 1, 5 or 10 mg kg-1 had little or no effect on the tumour weight, tumour prostanoid content, metastasis to the lymph nodes or lungs, or on the increase of mouse longevity by the cytotoxic drugs.