Is aplastic anaemia due to abnormality of D.N.A.?

Lymphocytes from eleven patients with aplastic anaemia were cultured with various agents which interact with D.N.A., and the proliferative responses to phytohaemagglutinin were measured. Lymphocytes from seven of the eleven patients were unduly sensitive to bleomycin, an agent causing strand breaks in D.N.A. The findings suggest that D.N.A. in these seven patients was abnormal, possibly as a result of an abnormality of D.N.A. repair. It is suggested that in aplastic anaemia D.N.A. damage in stem cells may lead to a failure of proliferation.

Comparative studies on the antitumor effect on intravenous administration of carbazilquinone and mitomycin-C

Comparison between Carbazilquinone and Mitomycin-C, both of which contain aziridinyl, carbamoyloxy, and quinonyl groups, was made for their therapeutic effect upon intravenous administration. Although both agents exhibited a significant effect on plasmacytoma X5563 in C3H/He mice to a similar extent, Mitomycin-C was not as effective on lympholeukemia L-1210 and on the lung metastasis of Ehrlich carcinoma in (C57BL/6 X DBA/2)F1 (BDF1) mice as was Carbazilquinone. Possible interpretations regarding this discrepancy are discussed.

Phase I study of oral mitomycin C

This study demonstrates that the gastrointestinal absorption of oral mitomycin C is variable and that myelosuppression correlates most closely with the peak serum concentration. The probable maximal-tolerated dose of oral mitomycin C is 45-50 mg/m2.

Skeletal malformations induced by mitomycin C in chick embryos

One hundred and eighty chick embryos were studied for the presence of skeletal malformations after administration of mitomycin C at 72, 96 and 120 hours of incubation. Axial skeleton defects included those of ribs, vertebrae, beak and crania. Appendicular skeletal defects were mainly confined to the lower limbs e.g. absence of phalanges, bent and shortened femur, fibula, tibia and metatarsus, in that order. Absence of phalanges and curved scapulae were noted in the upper limbs. The length of femur, tibia and metatarsus was significantly reduced (P less than 0.001) compared with the corresponding controls especially in the group treated at 96 h.

Mitomycin C in large infrequent doses in breast cancer

Seventy-one women with far-advanced breast cancer resistant to standard chemotherapeutic agents were administered mitomycin C using an intermittent high dose schedule. One group consisted of 54 patients with measurable metastatic tumor; a second group consisted of 18 patients with nonmeasurable osseous metastases. Objective response rate in group 1 was 26% for an average duration of 2 1/2 months. Subjective response rate in group 2 was 44% for an average duration of 3 months. Response and toxicity data were similar to those of studies employing the less convenient protracted low-dose schedule. Prior treatment with other alkylating agents did not adversely affect response. Further investigation into the role of mitomycin in combination chemotherapy programs is recommended.

The role of drug transport in resistance to nitrogen mustard and other alkylating agents in L518Y lymphoblsts

An investigation was undertaken of the mechanism of resistance to nitrogen mustard (HN2) and other alkylating agents, with particular emphasis on the interaction between cross-resistance and drug transport mechanisms in L5178Y lymphoblasts. Dose-survival curves demonstrated that the D0 for HN2-sensitive cells (L5178Y) treated with HN2 in vitro was 9.79 ng/ml and the D0 for HN2-resistant cells (L5178Y/HN2) was 181.11 ng/ml; thus, sensitive cells were 18.5-fold more responsive than were resistant cells and the difference was highly significant (p less than 0.001). A similar evaluation of 5 additional alkylating agents, including chlorambucil, melphalan, 1,3-bis(2-chloroethyl)-l-nitrosourea, Mitomycin C, and 2,3,5-tris(ethyleneimino)-1,4-benzoquinone, revealed that L5178Y/HN2 cells were also cross-resistant, in part, to each of these compounds. Furthermore, the degree of cross-resistance was remarkably similar; for each drug, dose-survival studies showed that HN2-resistant cells were approximately 2- to 3-fold more resistant to therapy than were sensitive cells. L5178Y/HN2 cells were also cross-resistant to cyclophosphamide in vivo; after treatment with cyclophosphamide, DBA/2 female mice that were given inoculations of L5178Y cells, but not those given transplants of L5178Y/HN2 cells, showed a significant prolongation of survival time (p less than 0.01). Transport of HN2, hydrolyzed derivative of HN2 and choline by L5178Y lymphoblasts in vitro was not competitively inhibited by any of the other alkylating agents, suggesting that transport of these compounds was by an independent mechanism. These findings suggest that the mechanism whereby L5178Y/HN2 cells are cross-resistant to other alkylating agents may involve nontransport factors and that these other drugs may bypass a major portion of HN2 resistance by using independent transport systems.