Synthesis and evaluation of several new (2-chloroethyl)nitrosocarbamates as potential anticancer agents.

Seven new (2-chloroethyl)nitrosocarbamates have been synthesized as potential anticancer alkylating agents. These compounds were designed with carrier moieties that would either act as prodrugs or confer water solubility. All compounds were screened in an in vitro panel of five human tumor cell lines: CAKI-1 (renal), DLD-1 (colon), NCI-H23 (lung), SK-MEL-28 (melanoma), and SNB-7 (CNS). Several agents showed good activity with IC(50) values in the range of 1-10 microg/mL against at least two of the cell lines. One compound, carbamic acid, (2-chloroethyl)nitroso-4-acetoxybenzyl ester (3), was selected for further study in vivo against intraperitoneally implanted P388 murine leukemia. In addition to the aforementioned compound, both carbamic acid, (2-chloroethyl)nitroso-4-nitrobenzyl ester (9) and carbamic acid, (2-chloroethyl)nitroso-2,3,4, 6-tetra-O-acetyl-1-alpha,beta-D-glucopyranose ester (24) were evaluated against subcutaneously implanted M5076 murine sarcoma in mice. None of these compounds were active in vivo.

In vivo gene therapy of cancer with E. coli purine nucleoside phosphorylase.

We have developed a new strategy for the gene therapy of cancer based on the activation of purine nucleoside analogs by transduced E. coli purine nucleoside phosphorylase (PNP, E.C. 2.4.2.1). The approach is designed to generate antimetabolites intracellularly that would be too toxic for systemic administration. To determine whether this strategy could be used to kill tumor cells without host toxicity, nude mice bearing human malignant D54MG glioma tumors expressing E. coli PNP (D54-PNP) were treated with either 6-methylpurine-2'-deoxyriboside (MeP-dR) or arabinofuranosyl-2-fluoroadenine monophosphate (F-araAMP, fludarabine, a precursor of F-araA). Both prodrugs exhibited significant antitumor activity against established D54-PNP tumors at doses that produced no discernible systemic toxicity. Significantly, MeP-dR was curative against this slow growing solid tumor after only 3 doses. The antitumor effects showed a dose dependence on both the amount of prodrug given and the level of E. coli PNP expression within tumor xenografts. These results indicated that a strategy using E. coli PNP to create highly toxic, membrane permeant compounds that kill both replicating and nonreplicating cells is feasible in vivo, further supporting development of this cancer gene therapy approach.

Lack of in vivo crossresistance with gemcitabine against drug-resistant murine P388 leukemias.

Gemcitabine, a novel pyrimidine nucleoside antimetabolite, has shown clinical antitumor activity against several tumors (breast, small-cell and non-small-cell lung, bladder, pancreatic, and ovarian). We have developed a drug-resistance profile for gemcitabine using eight drug-resistant P388 leukemias in order to identify potentially useful guides for patient selection for further clinical trials of gemcitabine and possible noncrossresistant drug combinations with gemcitabine. Multidrug-resistant P388 leukemias (leukemias resistant to doxorubicin or etoposide) exhibited no crossresistance to gemcitabine. Leukemias resistant to vincristine (not multidrug resistant), cyclophosphamide, melphalan, cisplatin, and methotrexate were also not crossresistant to gemcitabine. Only the leukemia resistant to 1-beta-D-arabinofuranosylcytosine was crossresistant to gemcitabine. The results suggest that (1) it may be important to exclude or to monitor with extra care patients who have previously been treated with 1-beta-D-arabinofuranosylcytosine and (2) the lack of crossresistance seen with gemcitabine may contribute to therapeutic synergism when gemcitabine is combined with other agents.

Cross-resistance of drug-resistant murine P388 leukemias to taxol in vivo.

The antimicrotubule agent taxol (NSC 125973) has shown clinical antitumor activity against several classically refractory tumors. We developed a drug-resistance profile for taxol using ten drug-resistant P388 leukemias to identify potentially useful guides for patient selection for further clinical trials of taxol and possible non-cross-resistant drug combinations with taxol. Multidrug-resistant P388 leukemias exhibited either clear (leukemia resistant to amsacrine) or marginal cross-resistance (leukemias resistant to doxorubicin, actinomycin D, and mitoxantrone) to taxol. Leukemias resistant to vincristine (non-multidrug-resistant leukemia), camptothecin, melphalan, cisplatin, 1-beta-D-arabinofuranosylcytosine, and methotrexate were not cross-resistant to taxol. The data suggest that (1) it may be important to exclude or to monitor with extra care patients who have previously been treated with amsacrine, doxorubicin, actinomycin D, or mitoxantrone and (2) a combination of one of the non-cross-resistant drugs and taxol might exhibit therapeutic synergism.

Antitumor drug cross-resistance in vivo in a cisplatin-resistant murine P388 leukemia.

Since 1978, over 50 clinically useful antitumor drugs or new candidate antitumor agents have been evaluated in vivo against cisplatin-resistant P388 leukemia (P388/DDPt) in our laboratories. Analysis of this data base has yielded insights into the cross-resistance, collateral sensitivity, and mechanisms of resistance of P388/DDPt. P388/DDPt was cross-resistant or marginally cross-resistant to eight agents [carmethizole.HCl, rhizoxin, dibromodulcitol, spirohydantoin mustard, hepsulfam, arabinosyl-5-azacytosine (ara-AC), tiazofurin, and deoxyspergualin]. Of these eight agents, the latter six have entered various phases of clinical trials. For these trials, it may be important to exclude or to monitor with extra care patients who have previously been treated with cisplatin. P388/DDPt was collaterally sensitive to six agents [fludarabine phosphate (2-F-ara-AMP), amsacrine (AMSA), mitoxantrone, etoposide (VP-16), batracylin, and flavone acetic acid] and, possibly, to two others (merbarone and echinomycin). These observations of collateral sensitivity suggest that a combination of cisplatin plus any one of these drugs might exhibit therapeutic synergism. Therapeutic synergism has been observed in animal models for combinations of cisplatin plus VP-16, AMSA, or mitoxantrone. The observation of collateral sensitivity for P388/DDPt to four agents (AMSA, mitoxantrone, merbarone, and VP-16) that have been reported to interact with DNA topoisomerase II suggests the possible involvement of the latter in cisplatin resistance. Both the increased sensitivity of P388/DDPt to these agents and a portion of its resistance to cisplatin could be the result of an increase in DNA topoisomerase II activity.