Reduced membrane protein associated with resistance of human squamous carcinoma cells to methotrexate and cis-platinum.

A membrane protein recognized by monoclonal antibody SQM1 was identified in human squamous carcinomas, including those originating in the head and neck (SqCHN), lung and cervix. Cell lines derived from SqCHN of previously untreated patients expressed high amounts of this protein. In contrast, many cell lines established from SqCHN of patients previously treated with chemotherapy and/or radiation showed diminished amounts of this SQM1 protein. The expression of SQM1 antigen was determined in several SqCHN cell lines made resistant by exposure to methotrexate (MTX) in vitro. The parent cell lines all exhibited strong binding to SQM1 antibody. The MTX-resistant sublines showed much lower membrane binding of SQM1. The lowest SQM1 reactivity was found in cell lines with high resistance to MTX and with diminished rate of MTX transport. Some highly MTX-resistant cell lines which had high levels of dihydrofolate reductase, but which retained a high rate of MTX transport, also retained high levels of SQM1 binding. Reduced SQM1 protein was also found in SqCHN cells which developed resistance to the alkylating drug cis-latinum (CDDP) and which showed reduced membrane transport of CDDP. Cell growth kinetics and non-specific antigenic shifts were not responsible for the differences in SQM1 binding between the parent cell lines and their drug-resistant sublines. The finding of a novel protein which is reduced in cells resistant to MTX and CDDP could contribute to our understanding of the basic mechanisms of drug resistance. By detecting SQM1 protein in clinical specimens, it may be possible to monitor the development of drug resistance in tumors.

Platinum complexes inhibit repair of potentially lethal damage following bleomycin treatment.

The SCC-25 cell line is a well-established line derived from a human squamous carcinoma of the head and neck. The capacity of this cell line for recovery from potentially lethal damage following X-ray treatment has been documented. The survival curve of stationary phase SCC-25 cells exposed to various concentrations of bleomycin is biphasic with an initial sensitive phase and a less sensitive second phase as is common for many cell lines. Stationary phase SCC-25 cells were exposed to 100 mU ml-1 of bleomycin for 1 h. The drug was removed and the cells were allowed various periods to recover from potentially lethal damage. After 24 h, the SCC-25 cells showed a recovery ratio (R/R0) of 7.0 which corresponded to an immediate survival at a drug level of 27 mU ml-1, a dose 3.7-fold less than the exposure concentration of 100 mU ml-1. Over the course of the first 4 h following bleomycin exposure, 0.5 microM CDDP was a very effective inhibitor of potentially lethal damage repair, giving a R/R0 of 1.1 or nearly complete inhibition of recovery. Between 2 and 4 h the R/R0 was 1.6-1.8 with CDDP and 4.1-5.3 without CDDP indicating appreciable inhibition of recovery. Plant (10 microM) and Plato (10 microM) produced potentially lethal damage recovery inhibition patterns very similar to that of CDDP. After 1 h the recovery ratios in the presence of Plant and Plato were 1.1-1.3. Between 2 and 4 h, Plato and Plant gave recovery ratios of 1.8-2.3 and 1.6-1.9, respectively. NIPt and Pt(terpy) were examined at both 10 microM and 25 microM for their ability to inhibit potentially lethal damage recovery after bleomycin treatment. After 1 h, NIPt gave a recovery ratio of 1.3-1.4, and after 2-4 h the recovery ratio was 1.7-2.6. Pt(terpy) gave recovery ratios of 1.3-1.6 after 1 h and 1.5-1.8 after 24 h.

The effect of chemotherapeutic agents on human oral squamous cell carcinoma transplanted to nude mice: a histologic study.

Clearly differentiated squamous cell carcinomas were transplanted to the backs of nude mice; tumor cells of a human tongue carcinoma cell line were used. Animals bearing tumors that measured at least 4 mm in diameter were treated with either methotrexate (MTX), cis-diamminedichloroplatinum II (CDDP) or bleomycin intraperitoneally for 5 days. Histologic evaluation of tumors obtained 24 hours after the last injection revealed degenerative and necrotic morphology in all treatment groups. The histologic alterations were observed prior to any clinical evidence of tumor shrinkage. The most impressive changes were found in CDDP-treated tumors, with creation of large pseudocysts containing necrotic material and cell debris. Pseudocyst formation was less obvious in MTX-treated animals and was absent in bleomycin-treated tumors. Drug treatment had no obvious influence on the keratinization in tumors. The findings suggest that the nude mouse model may be useful for the histologic determination of drug-induced effects on tumors in human beings.

SQM1 antibody defines a surface membrane antigen in squamous carcinoma of the head and neck.

We produced murine monoclonal antibodies (MAbs) directed against the surface membrane of squamous-cell carcinoma of the head and neck (SCCHN). One antibody, SQM1, was determined by immunofluorescence and radioimmunoassay to be reactive with 13/13 SCCHN cell lines derived from different sites of the head and neck area. No binding reaction was observed with normal fibroblasts, red blood cells, nucleated bone-marrow cells or epithelial cells from normal oral mucosa. SQM1 reactivity was observed with primary cultures of normal epidermal and bronchial epithelial cells. Significant reactivity was found with 2/4 cell lines derived from small-cell carcinoma of the lung but little or no reactivity was found with other lung cancer cell lines. Various cell lines derived from other cancers including breast, colon, and ovarian carcinomas, melanoma, neuroblastoma and leukemia were generally unreactive. Seventeen out of 18 fresh frozen specimens of SCCHN were strongly reactive with SQM1 antibody. However, autopsy specimens from the heart, liver, kidney, spleen, colon, subcutaneous fat and skin connective tissue were unreactive. SQM1 antibody may be useful in biological and clinical studies of the head and neck region.