Aphidicolin (AP) or hydroxyurea (HU) inhibited DNA repair and enhanced cytotoxicity in human ovarian carcinoma cells A2780 treated with L-phenylalanine mustard (L-PAM) combined with cisplatin or thioTEPA, and in the cells treated with cisplatin combined with thioTEPA. In cultures treated with L-PAM or cisplatin alone post-treatment with AP or HU had no effect on DNA repair and produced only additive cytotoxicity. Post-treatment with AP + HU inhibited DNA repair and enhanced cell killing in cultures treated with L-PAM alone. The inhibitor of protein synthesis cycloheximide protected cells from the cytotoxicity of AP + HU but had no effect on synergistic cell killing produced by DNA repair inhibition. In cisplatin-resistant cells A2780/CP post-treatment with AP + HU enhanced the cytotoxicity of L-PAM, but not of cisplatin. However, in resistant cells treated with cisplatin combined with L-PAM or thioTEPA DNA repair inhibitors decreased IC90 of cisplatin. Treatment of cells with two alkylating agents enhanced the sensitivity to DNA repair inhibitors and eliminated low sensitivity to inhibitors of repair associated with drug resistance.

Alkylating Agents↗

PubMedDate not supplied

Apoptosis in human breast and gastrointestinal carcinomas. Detection in histological sections with monoclonal antibody to single-stranded DNA.

We report application of a novel immunohistochemical procedure for the staining of apoptotic (AP) cells in paraffin sections using monoclonal antibody (MAb) to single-stranded DNA. MAb differentiated between apoptosis and necrosis and in contrast to in situ end labelling specifically stained only AP cells. AP carcinoma cells stained with the antibody were detected in 32 of 58 infiltrating human breast carcinomas and in 9 of 15 colon adenocarcinomas. Stromal cells stained with the MAb were observed in all carcinomas, including those in which no AP carcinoma cells were detected. There was a strong positive correlation between the presence of AP cells, loss of hormone receptors and a high proliferation rate in breast carcinomas. AP cells were present in 80-87% of receptor-negative carcinomas, while most of receptor-positive breast carcinomas did not contain AP cells. Apoptosis in tumor cells was detected significantly more frequently among breast carcinomas with high, than among carcinomas with low S-phase fraction. AP cells were present in 93-95% of breast carcinomas which were receptor-negative and had a high S-phase fraction. Immunostaining demonstrated a strong positive correlation between the loss of bcl-2 protein and intensive apoptosis in breast carcinomas. Association between apoptosis and markers of poor prognosis in breast cancer (loss of hormone receptors, intensive proliferation, loss of bcl-2 protein) indicates that apoptotic cell death is typical of more aggressive carcinomas.

Adenocarcinoma↗