Cancer research
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Cephalosporin doxorubicin (C-Dox) and 7-(4-carboxybutanamido)-cephalosporin mustard (CCM) are prodrugs that are catalytically converted by Enterobacter cloacae beta-lactamase (bL) to the active anticancer agents doxorubicin and phenylenediamine mustard, respectively. Both prodrugs were less cytotoxic to the 3677 human melanoma line than their respective drugs and were activated in an immunologically specific manner by 96.5-bL, a mAb-bL conjugate that binds to 3677 cell surface antigens. Similar results were obtained using the CCM prodrug on SK-MEL 28 human melanoma cells. ⋯ In contrast, when CCM was used as a prodrug, cures of established 3677 tumors were obtained in 80% of the 96.5-bL treated animals. This combination was also able to induce regressions of large 3677 tumor masses (800 mm3) without any apparent toxic side effects. We conclude that 96.5-bL in combination with C-Dox or CCM has greater antitumor activity than systemic treatment with the corresponding drugs and that CCM is a more effective prodrug than C-Dox for treating human 3677 melanoma xenografts.
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Human prostatic cancer cells have a remarkably low rate of proliferation even when they have metastasized to the bone and have become androgen independent (Berges et al., Clin. Cancer Res., 1:473-480, 1995). Due to this low proliferation, patients with such androgen-independent metastatic prostatic cancer cells are rarely treated successfully with the presently available chemotherapeutic agents. ⋯ Linomide treatment increased this necrotic percentage to 59 +/- 2% [i.e., 48% increase (P < 0.05)]. Linomide therapy also increased apoptotic cell death in non-necrotic tumor areas. In the untreated TSU tumors, 2.9 +/- 0.6% of tumor cells were apoptotic in the non-necrotic areas, and in the linomide-treated TSU tumors this percentage increased to 3.6 +/- 0.4% [i.e., 24% increase (P < 0.05)].(ABSTRACT TRUNCATED AT 400 WORDS)
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LU103793 (NSC D-669356) is a new synthetic derivative of Dolastatin 15, an antiproliferative compound which was isolated from the mollusk Dolabella auricularia. Like Dolastatin 15, LU103793 is highly cytotoxic in vitro (IC50 = 0.1 nM). To investigate the mechanism of action of LU103793, we used a combination of biochemical and cellular methods. ⋯ At the cellular level, it induced depolymerization of microtubules in interphase cells and development of abnormal spindles and chromosome distribution in mitotic cells. Although these effects are very similar to the cellular alterations caused by vinblastine, LU103793 does not inhibit vinblastine binding to unpolymerized tubulin in vitro. Our results suggest that LU103793 exerts its cytotoxic activity primarily through disruption of microtubule organization.
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mAbs reactive with epitopes expressed on tumor vessels were evaluated as universal delivery agents of peptides with vasoactive properties to enhance the uptake of macromolecules in tumors. Unlike other reported approaches to target tumor vessels, a mAb designated TV-1 targets a basement membrane antigen that is found in all tissues but that is accessible only in tumor vessels, making it an alternative vehicle for the delivery of biologically active peptides to tumors. A panel of 30 monoclonal and polyclonal antibodies was screened by immunohistochemistry on sections of human tumors, normal vascular endothelium, and connective tissues. ⋯ When TV-1/IL-2 was compared with the specific vasoconjugate (Lym-1/IL-2) as a pretreatment in the Raji lymphoma model, which has low vascularization, TV-1/IL-2 yielded approximately 60% of the tumor uptake seen with Lym-1/IL-2. In comparison, pretreatment with TV-1/IL-2 in the LS174T colon carcinoma model, which has high vascularization, yielded approximately the same tumor uptake seen with the B72.3/IL-2 vasoconjugate, which directly targets the tumor cells. These studies demonstrate that a mAb directed against fibronectin in the endothelial subcellular matrix can be used to deliver vasoactive agents to tumors.
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Comparative Study
In vitro and in vivo activities of a doxorubicin prodrug in combination with monoclonal antibody beta-lactamase conjugates.
A cephalosporin derivative of doxorubicin (C-Dox) was evaluated as a prodrug for activation by mAb conjugates of the beta-lactamase from Enterobacter cloacae P99 (beta L; EC 3.5.2.6). The conjugates consisted of beta L and the F(ab') fragments of either of the mAbs L6, P1.17, or 96.5. L6 binds to antigens on a variety of carcinomas, including the two lung adenocarcinoma cell lines H2981 and H2987 used in this study. 96.5 binds to the melanoma-associated antigen p97, and P1.17 was used for the control conjugate. ⋯ This finding suggested that the conversion of C-Dox to Dox was tumor specific and dependent on the presence of the targeted antigen. Furthermore, the best antitumor activity against both H2981 and H2987 tumors was obtained by treatment with L6-beta L and C-Dox compared to P1.17-beta L and C-Dox or Dox alone. Thus, higher levels of Dox corresponded to greater therapeutic effects in both of the tumor models studied.