Makio Gamo

Screening the p53 status of human cell lines using a yeast functional assay

We have screened the p53 status of 156 human cell lines, including 142 tumor cell lines from 27 different tumor types and 14 cell lines from normal tissues by using functional analysis of separated alleles in yeast. This assay enables us to score wild‐type p53 expression on the basis of the ability of expressed p53 to transactivate the reporter gene HIS3 via the p53‐responsive GAL1 promoter in Saccharomyces cerevisiae. Of 142 tumor cell lines, at least 104 lines (73.2%) were found to express the mutated p53 gene: 94 lines (66.2%) were mutated in both alleles, three lines (2.1%) were heterozygous, and no p53 cDNA was amplified from seven lines (4.9%). Of the 14 cell lines originating from normal tissues, all the transformed or immortalized cell lines expressed mutant p53 only. Yeast cells expressing mutant p53 derived from 94 cell lines were analyzed for temperature‐sensitive growth. p53 cDNA from eight cell lines showed p53‐dependent temperature‐sensitive growth, growing at 30°C but not at 37°C. Four temperature‐sensitive p53 mutations were isolated: CAT→CGT at codon 214 (H214R), TAC→TGC at codon 234 (Y234C), GTG→ATG at codon 272 (V272M), and GAG→AAG (E285K). Functionally wild‐type p53 was detected in 38 tumor cell lines (26.8%) and all of the diploid fibroblasts at early and late population doubling levels. These results strongly support the previous findings that p53 inactivation is one of the most frequent genetic events that occurs during carcinogenesis and immortalization. Mol. Carcinog. 19:243–253, 1997.

FDG PET evaluation of residual masses and regrowth of abdominal lymph node metastases from colon cancer compared with CT during chemotherapy

Fluorine-18-2-deoxy-2-fluoro-D-glucose (F-18 FDG) PET may be more suitable for follow-up after cancer treatment than other morphologic approaches, because it reflects tumor viability. A patient with abdominal lymph node metastases from colon cancer was followed by CT and F-18 FDG PET during chemotherapy. F-18 FDG PET tumor images changed in accordance with the clinical progress, whereas CT findings were relatively unchanged. This case clearly shows the utility of F-18 FDG PET for follow-up during cancer chemotherapy.

Enhancement of the efficacy of anticancer drugs with electroporation: Successful electrochemotherapy against gastric cancer cell lines in vivo and in vitro

BackgroundThe purpose of this study was to determine whether micropore formation caused by application of an electric current can increase the influx of anticancer drugs across cancer cell membranes with a concomitant increase in dose intensity and, therefore, toxicity to cancer cells.MethodsTwo cell lines, GCIY and KATO III, both established from human gastric cancers, were used as target cells to assess the effects of combining electroporation and anticancer drug therapy. Results were measured as the proliferation of cells to 50% of the value in control mice (IC50).ResultsWhen GCIY cells were used as targets in vitro, the IC50 value for bleomycin was decreased significantly by the electroporation, to 10−4 of the dose for the chemotherapeutic agent alone, and the IC50 values of cisplatin and 5-fluorouracil were decreased to one tenth of their baseline values. In the case of KATO III cells, the IC50 value for bleomycin was reduced by 10−2, but that of cisplatin did not change. The IC50 value for doxorubicin did not change when GCIY cells, showing multidrug resistance, or when KATO III cells, lacking multidrug resistance, were subjected to electroporation. When GCIY cells were transplanted subcutaneously into nude mice, the resultant tumors decreased to a minimum size at 2 weeks after combined treatment with bleomycin and electroporation.ConclusionElectroporation seems to be a promising adjunct to cancer chemotherapy.