Resistance of human leukemic and normal lymphocytes to drug-induced DNA cleavage and low levels of DNA topoisomerase II.

Adriamycin, amsacrine, and etoposide produce protein-associated DNA breaks in numerous cell types. However, in vitro exposure to Adriamycin (0.1-50.0 micrograms/ml) resulted in no detectable DNA cleavage in lymphocytes from patients with B-cell chronic lymphocytic leukemia (CLL) or in either B- or T-lymphocytes from normal donors. In contrast, DNA cleavage was observed in T-cells from CLL patients. Exposure to amsacrine or etoposide caused at least 50-fold less DNA cleavage in CLL and normal lymphocytes as compared to L1210 cells. These findings cannot be accounted for by differences in drug uptake. An attempt was made to explain the relative resistance of human lymphocytes to drug-induced DNA cleavage. DNA topoisomerase II, an intracellular target of tested drugs, was assayed in CLL and normal human blood lymphocytes by immunoblotting. The enzyme was detected neither in unfractionated lymphocytes nor in the enriched B- and T-cells from 28 untreated patients with CLL (Stage 0-IV) and from seven normal donors. Exponentially growing L1210 cells had approximately 7 x 10(5) enzyme copies per cell, suggesting a 100-fold higher content than that of CLL or normal lymphocytes. There were, however, detectable levels of DNA topoisomerase II in cells obtained from patients with diffuse histiocytic, nodular poorly differentiated and nodular mixed lymphomas, in Burkitt's lymphoma, acute lymphoblastic leukemia and CLL with prolymphocytic transformation. DNA topoisomerase I, a potential target for anticancer chemotherapy, was detectable in CLL and normal lymphocytes, as well as in cells of other malignancies tested. The above results may offer an explanation for the ineffectiveness of Adriamycin in the treatment of CLL. It could be suggested that low levels of DNA topoisomerase II contribute to drug resistance operating in human malignancies with a large compartment of nonproliferating cells.

Multimodal therapy for locally advanced breast cancer.

Thirty-one women with stage III breast cancer were prospectively treated with two cycles of cyclophosphamide (Cytoxan), doxorubicin hydrochloride (Adriamycin), fluorouracil, and tamoxifen citrate followed by a simple mastectomy with level I axillary dissection. Postoperatively, four additional cycles of the combination chemotherapy alternating with three cycles of 1500 rad (15 Gy) to the chest wall and lymphatics were given. Seventy-seven percent of patients had a greater than 50% reduction in tumor size after the initial chemotherapy. No tumor size progressed during therapy, and a single patient remained inoperable. Pathologic findings revealed nine patients with only microscopic residual tumor. Nuclear vacuolization was present in 42.8% of tumor cells after chemotherapy vs 14.2% of cells before chemotherapy. The mean follow-up for the groups is 24.3 months. To date, nine patients have had recurrence with only one isolated local recurrence. This therapy is effective in reducing primary tumor size and allows a limited mastectomy to be done with minimal morbidity.