Chemo-radioresistance of small cell lung cancer cell lines derived from untreated primary tumors obtained by diagnostic bronchofiberscopy

Clinically relevant radioresistant cells efficiently repair DNA double-strand breaks induced by X-rays

Radiotherapy is one of the major therapeutic modalities for eradicating malignant tumors. However, the existence of radioresistant cells remains one of the most critical obstacles in radiotherapy and radiochemotherapy. Standard radiotherapy for tumor treatment consists of approximately 2 Gy once a day, 5 days a week, over a period of 5-8 weeks. To understand the characteristics of radioresistant cells and to develop more effective radiotherapy, we established a novel radioresistant cell line, HepG2-8960-R with clinical relevance from parental HepG2 cells by long-term fractionated exposure to 2 Gy of X-rays. HepG2-8960-R cells continued to proliferate with daily exposure to 2 Gy X-rays for more than 30 days, while all parental HepG2 cells ceased. After exposure to fractionated 2 Gy X-rays, induction frequencies of micronuclei and remaining foci of gamma-H2AX in HepG2-8960-R were less than those in HepG2. Flow cytometric analysis revealed that the proportion of cells in S- and G2/M-phase of the cell cycle was higher in HepG2-8960-R than in HepG2. These suggest that the response of clinically relevant radioresistant (CRR) cells to fractionated radiation is not merely an accumulated response to each fractionated radiation. This is the first report on the establishment of a CRR cell line from an isogenic parental cell line.

Expression of the Wilms' tumor gene WT1 in solid tumors and its involvement in tumor cell growth

To determine the role of the Wilms' tumor gene WT1 in tumorigenesis of solid tumors, expression of the WT1 gene was examined in 34 solid tumor cell lines (four gastric cancer cell lines, five colon cancer cell lines, 15 lung cancer cell lines, four breast cancer cell lines, one germ cell tumor cell line, two ovarian cancer cell lines, one uterine cancer cell line, one thyroid cancer cell line, and one hepatocellular carcinoma cell line) by means of quantitative reverse transcriptase-polymerase chain reaction. WT1 gene expression was detected in three of the four gastric cancer cell lines, all of the five colon cancer cell lines, 12 of the 15 lung cancer cell lines, two of the four breast cancer cell lines, the germ cell tumor cell line, the two ovarian cancer cell lines, the uterine cancer cell line, the thyroid cancer cell line, and the hepatocellular carcinoma cell line. Therefore, of the 34 solid tumor cell lines examined, 28 (82%) expressed WT1. Three cell lines expressing WT1 (gastric cancer cell line AZ-521, lung cancer cell line OS3, and ovarian cancer cell line TYK-nu) were further analyzed for mutations and/or deletions in the WT1 gene by means of single-strand conformation polymorphism analysis. However, no mutations or deletions were detected in the region of the WT1 gene ranging from the 3' end of exon 1 to exon 10 (the WT1 gene consists of 10 exons) in these three cell lines. Furthermore, when AZ-521, OS3, and TYK-nu cells were treated with WT1 antisense oligomers, the growth of these cells was significantly inhibited in association with a reduction in WT1 protein levels. Furthermore, constitute expression of the transfected WT1 gene in cancer cells inhibited the antisense effect of WT1 antisense oligomer on cell growth. These results indicated that the WT1 gene plays an essential role in the growth of solid tumors and performs an oncogenic rather than a tumor-suppressor gene function.

Detailed deletion mapping of the short arm of chromosome 3 in small cell and non-small cell carcinoma of the lung

We constructed a detailed deletion map of the short arm of chromosome 3 (3p) for 55 lung cancer cases by using 17 restriction fragment length polymorphism (RFLP) probes. Initially, we examined 40 small cell lung cancer (SCLC) cases and found three regions of deletion at 3p25-26, 3p21.3 and 3p14-cen, suggesting the possibility of at least three different tumor-suppressor genes on 3p. In order to obtain more detailed deletion area, and to compare the pattern of 3p deletion, we also examined 15 non-small cell lung cancer (NSCLC) cases. Compared to NSCLC cases, most of SCLC cases have widespread deletion on 3p, suggesting multiple tumor-suppressor genes on 3p may be inactivated in this type of cancer. In 3p21.3 area, minimum overlapping area of deletion lays between two probes which are close to each other. These data will be useful to isolate the putative tumor-suppressor genes located on the chromosome 3p.

Complementary DNA sequence encoding the major neural cell adhesion molecule isoform in a human small cell lung cancer cell line

The neural cell adhesion molecule (N-CAM), a member of the immunoglobulin gene super-family mediating homophilic cell-cell adhesion in a neuroendocrine system, is preferentially expressed in human small cell lung cancer (SCLC). Immunoprecipitation of a panel of SCLC cell lines by monoclonal antibodies (mAbs) specific for N-CAM detects mainly the 145-kDa isoform. This result was correlated with Northern blotting where a single 6.2-kb mRNA was detected in nine SCLC cell lines. To determine cDNA sequence encoding the N-CAM isoform, we selected several cDNA clones encoding N-CAM isolated from OS2-R, a SCLC cell line established in our laboratory. Based on the analysis of the full-length cDNA obtained from two clones, the sequence of this 145-kDa isoform was shown to be essentially identical to that of the 140-kDa N-CAM isoform of neuroblastoma except for a single base pair changed at position 1620 without changing amino acid encoded.

Characterisation of a new mouse monoclonal antibody (ONS-M21) reactive with both medulloblastomas and gliomas

We developed an IgG1 mouse monoclonal antibody (ONS-M21) directed against a cell surface antigen of medulloblastomas and gliomas in immunisation of mice with the ONS-76 medulloblastoma cell line. The antibody specifically reacted with medulloblastomas, supratentorial primitive neuroectodermal tumours (SPNETs) and gliomas, but not with other neuroectodermally derived tumours (neuroblastoma and melanoma) or with other kinds of tumours (meningioma, neurinoma, leukaemia, and small cell lung cancer). No reactivity was identified with normal body tissues, including peripheral blood cells. Characterisation of the ONS-M21 antigen showed that it was a trypsin-sensitive glycoprotein with a molecular weight of 80 kDa on SDS-PAGE. The pattern of reactivity and the biochemical properties of this antigen were different from those of other markers of medulloblastoma. These results indicate that ONS-M21 detects a new tumour-associated cell surface antigen specifically expressed by medulloblastomas, SPNETs, and gliomas. This is the first report that medulloblastomas may share common cell surface antigens with gliomas, although most studies have concluded that medulloblastoma has a predominantly neuronal phenotype. The lack of reactivity with normal tissue implies that ONS-M21 has potential applications as both a diagnostic tool and a therapeutic agent.

High sensitivity to peripheral blood lymphocytes and low HLA-class I antigen expression of small cell lung cancer cell lines with diverse chemo-radiosensitivity

Three cell lines of small cell lung cancer (SCLC), which were established from specimens of untreated primary tumors biopsied by diagnostic bronchofiberscopy, were analyzed for immunological characteristics. These cell lines showed considerable heterogeneity in chemo-radiosensitivity, which was well correlated with clinical responses of the respective tumors, but their HLA-class I antigen expressions were equally depressed and they were susceptible to peripheral blood lymphocytes (PBL) and lymphokine-activated killer (LAK) cells, irrespective of their diverse chemo-radiosensitivity. Treatment of the cell lines with recombinant immune interferon (rIFN-gamma) increased their HLA-class I antigen expression and conversely depressed PBL sensitivity but not LAK sensitivity. This inverse relationship between HLA-class I expression and PBL susceptibility was also demonstrated using other pairs of autologous PBL and SCLC cell lines. rIFN-gamma changed neither HLA-class II antigen nor SCLC-specific antigen expression under the same experimental conditions. In vitro immunization of allogeneic peripheral blood lymphocytes with rIFN-gamma-treated SCLC cells induced allo-specific killer cells which lysed rIFN-gamma-treated more strongly than non-treated SCLC cells. These results suggest that reduced HLA-class I antigen expression of SCLC could protect the cancer from attack of killer T cells in spite of the higher sensitivity to PBL or LAK cells.

Two monoclonal antibodies against small-cell lung cancer show existence of synergism in binding

Murine IgG1 monoclonal antibodies (mAbs), ITK-2 and ITK-3, were generated against a small-cell lung cancer (SCLC) cell line. Enzyme-linked immunosorbent assay using a variety of established cell lines as substrates, immunoperoxidase staining of freshly frozen tissue sections, and fluorescence-activated cell sorter analysis of peripheral blood leukocytes showed that these mAbs recognize a part of the SCLC-associated cluster 1 antigen. In immunoprecipitation studies, both ITK-2 and ITK-3 bound to a 145-kDa glycoprotein of SCLC cell membrane extracts, as did MOC-1 and NKH-1, which both recognize the cluster 1 antigen. However, because the binding of 125I-labeled ITK-2 to SCLC cells was not inhibited by MOC-1 or NKH-1, the binding site of ITK-2 on SCLC cells appeared to be different from that of either MOC-1 or NKH-1. Unexpectedly, binding of 125I-labeled ITK-2 to SCLC cells increased in the presence of ITK-3. This ITK-3-induced increase in ITK-2 binding was due partly to an increase in the number of binding sites for ITK-2 on SCLC cells. Addition of ITK-3 may, therefore, improve the effectiveness of ITK-2-based tumor detection or therapy.