Viral oncogene product of avian sarcoma virus S2 was reported to have two alterations from proto-src product; a substitution of its extreme carboxyl terminus with a peptide of helper viral protein and a point mutation which altered the 501st amino acid from arginine to lysine. However, the following data suggest that lysine⁵⁰¹ is more common in proto-src product than arginine⁵⁰¹. Proto-src from two independent embryos which we analyzed encoded lysine for the 501st amino acid. Rous sarcoma virus and S1, another isolate which had transduced proto-src, also coded for lysine at the same position. Thus, in the case of S2, the oncogenic activation of the src gene appeared to be achieved with only an alteration at its carboxyl terminus and enhanced expression by long terminal repeats.

View full abstract

A sensitive radioimmunoassay for human c-myc protein was developed by using an amino-terminal fragment of c-myc protein, c-myc(11-24). Immunoreactive c-myc protein was found to be present in 3 human tumors (HL-60, N231, Lu-65), which are known to have c-myc gene amplification. In contrast, c-myc protein was undetectable in 1 human tumor (H69) without c-myc gene amplification as well as in human heart tissues.

View full abstract

The biochemical basis for the cytotoxicity of 5-fluorouracil is still controversial; it is not clear whether the mechanism involves interference with DNA metabolism or incorporation of the drug into RNA. To distinguish between these two possibilities, we took advantage of a mutant strain of the mouse mammary tumor cell line FM3A that is deficient in thymidylate synthase, which is widely believed to be the target of 5-fluorouracil. We demonstrated that the target of the cytotoxicity of 5-fluorouracil was not thymidylate synthase; instead, the cytotoxicity was positively correlated with drug incorporation into RNA under conditions where thymidine increased the incorporation of 5-fluorouracil into RNA concentration-dependently.

View full abstract

The details of family histories naturally change as time passes. Thus, the family histories at the time of first consultation are incomplete, particularly in the cases of younger cancer patients whose disease is indicated as having a genetic background on the basis of epidemiological studies. The necessity for follow-up of the family history is illustrated by presenting some clinical cases as examples.

View full abstract

In order to further analyze the biological effects of phenobarbital (PB) and nafenopin (NAF) on rat hepatocarcinogenesis, four experiments were undertaken. In the first one, their “promoting” effect on an ongoing carcinogenic process was analyzed. Rats were initiated by diethylnitrosamine treatment (I) and submitted two weeks later to a selection procedure (S). One week after 2-acetylaminofluorene (2-AAF) release, the animals received for up to 56 weeks a basal diet or a diet containing 0.05% of PB or 0.1% of NAF. The quantitative analysis of the gamma-glutamyl-transferase-positive lesions showed that, 8 to 19 weeks after I, PB enhanced the development of preneoplastic lesions whereas NAF inhibited it as compared to a group receiving a basal diet. However, both compounds enhanced the incidence and the yield of liver cancer starting 27 weeks after I (67% and 95%, respectively, vs 10%). In the second experiment, the effect of chronic administration of PB and NAF given after I without S or after S without I was analyzed. Within a period of observation of 27 to 32 weeks, the incidence of cancer was 10% after I/PB and 75% after I/NAF. No cancer developed after S/PB, S/NAF or NAF alone. The third experiment was designed to test whether NAF had an initiating or selecting effect. The results of the quantitative analysis of he gamma-glutamyl-transferase-positive lesions showed that as compared to diethylnitrosamine, NAF had no initiating effect. When NAF replaced 2-AAF in the selection procedure, few gamma-glutamyl-transferase-positive lesions and no cancer were detected 8 and 32 weeks, after I. The fourth experiment indicated that NAF could not prevent the remodeling of preneoplastic lesions induced in the I/S protocol. Even though they both have a “promoting” effect in liver carcinogenesis as evidenced by the increased incidence and yield of cancer, PB and NAF act differently.

View full abstract

An N-ras transforming gene was detected in human rectal carcinoma-derived cells (7060) and molecularly cloned. The genetic lesion responsible for the transforming activity of the 7060 oncogene was localized to a single nucleotide transition from A to T in codon 61 of the predicted protein. This lesion in the second exon results in substitution of histidine for glutamine at this position. We also found an EcoRI restriction fragment length polymorphism, consisting of two alleles, of the human c-myb gene. The 7060-transformed epithelial cells showed the homozygous phenotype, while normal fibroblasts of the same patient showed the heterozygous phenotype. This suggests a relationship between the phenotypic change in the c-myb locus and the induction of the 7060 tumor.

View full abstract

Cancer prevalence statistics are necessary for cancer control programs. Although a long-term cancer registry keeps files which cover incidence, prevalence and cured cases, the latter two categories are difficult to distinguish from each other. The Connecticut and the Finnish Cancer Registries therefore defined the sum of these two groups as “prevalence.” The authors estimated the numbers and rates of survivors from cancer (“prevalence”) in Japan as of January 1, 1985, based on the number of cancer patients for all sites diagnosed since 1960. 1) The number of cancer patients in Japan diagnosed during the period from 1960 to 1984 was estimated to be 4, 686, 352 (both sexes). 2) Of these, the number of cancer survivors as of January 1, 1985 was estimated to be 952, 870 (both sexes). 3) Among the survivors, 430, 940 were diagnosed in the final five years from 1980-84. 4) The results were compared with those reported from the USA and Finland.

View full abstract

Yoshida sarcoma cells were incubated with each of 4 different saturated and 17 different unsaturated fatty acid methyl and ethyl esters in order to modify the fatty acid composition of the cell membrane, and a possible correlation between the lipid fluidity of the cell membrane and the metastatic efficiency was studied. Almost all the unsaturated fatty acids used were incorporated into the tumor cell membrane, resulting in an increase of fluidity. In contrast, the incorporation of saturated fatty acids brought no change in fluidity. Exogenous treatment of the cells with palmitoleic acid (16:1, cis) induced a remarkable increase of membrane lipid fluidity resulting in easier passage of modified cells through capillary vessels, which was detected in an in vitro perfusion test of the lung. Intravenous injection of the modified cells resulted in fewer metastatic foci in the lung as compared with that of unmodified cells. A similar effect on lung metastasis was also observed in exogenous modification of the cells by linoleic acid (18:2, cis) or linolenic acid (18:3, n-3). On the other hand, although exogenous eicosapentaenoic acid (20:5, n-3) and docosahexaenoic acid (22:6, n-3) treatments induced a slight increase in the lipid fluidity of the cells, intravenous injection of the cells produced a significant increase in their metastatic potential in the lung. Interestingly, the treatment with 20:5 and 22:6 produced increased stickiness of the cells to a glass surface and reduced cellular passage through the vessels as detected by the lung perfusion test. Thus, the present results suggested that selective modification of membrane fatty acid may be a useful method for artificial regulation of the ability of circulating tumor cells to pass through vessels.

View full abstract

The biosynthetic pathways of pyrimidine nucleotides were studied in cells obtained from 10 patients with acute leukemia (AL), 3 with chronic myelocytic leukemia in blastic crisis (CML-crisis) and 4 with chronic myelocytic leukemia (CML) and from 8 controls. In the de novo pathway, synthesis of intermediates was analyzed with NaH[¹⁴C]O₃ as a tracer. In the salvage pathway, the formation of nucleotides and free bases was studied with [³H]nucleosides (uridine, cytidine, thymidine, deoxyuridine, and deoxycytidine) tracers. Radioactivities of nucleotides were significantly lower in AL and CML-crisis cells than in CML and control cells in both pathways. These results suggest that the proliferative rate of cells was lower in the former cases than in the latter. Biosynthetic activities of nucleotides in the salvage pathway were about 100-300 times higher than those in the de novo pathway. It was calculated however, that as much as 70% of the amount of nucleic acids necessary for AL cells can be supplied by de novo biosynthesis, while in normal bone marrow cells the figure was about 30%. The greater part of pyrimidine biosynthesis can be carried out through the de novo pathway. In particular, AL cells with a longer generation time seemed to depend more on de novo biosynthesis than do normal bone marrow cells. This finding could be important in connection with the design of antileukemic agents.

View full abstract

The effects of bleomycin (BLM) on the survival of Burkitt lymphoma cells grown in vitro and in vivo were studied. Cells at the early plateau phase in culture were much more resistant to BLM than at the exponential phase. The late plateau-phase cells showed the highest sensitivity to the drug among the three phases of growth. After exposure to BLM, no recovery in survival was found for the cells in culture. Burkitt tumor in nude mice grew exponentially with about a threefold longer cell cycle time than the cells in culture, but the age-distribution of cells in the tumor was similar to that of the exponentially growing culture. The cells in the tumor were killed by BLM in a biphasic manner and did not show any significant recovery in survival after an injection of the drug, as found with the cells in culture. These findings indicate a deficiency in the repair of potentially lethal damage in Burkitt cells induced by BLM; this may be one of the reasons for the high sensitivity of the lymphoma to the drug.

View full abstract

An adriamycin (ADM)-resistant variant (K562/ADM) of human myelogenous leukemia K562 was established. K562/ADM was stable for 2 months in medium without ADM, and was 130-fold more resistant to ADM as compared to the parent K562. Twenty clones were isolated from K562/ADM by the limiting dilution technique. Five clones with different ADM sensitivity were selected and characterized further. The extent of clonal resistance to ADM was parallel to the extent of resistance to vincristine (VCR), except for one clone, KA-15. The majority of clones, including K562/ADM, accumulated far smaller amounts of daunomycin (DAU) or VCR as compared to the parent K562. However, a highly resistant clone did not necessarily accumulate less DAU in the cells, indicating that the mechanism of ADM resistance cannot be explained solely by a defect of ADM accumulation. All clones rapidly transported DAU and VCR from the cells. K562/ADM expressed on the cell surface three distinct glycoproteins with molecular weights of 180, 000, 83, 000 and 65, 000 daltons. No change was detected in the actin and tubulin contents of K562 and clones. K562/ADM and its clones expressed double minute chromosomes and contained homogeneously staining regions in the chromosomes.

View full abstract

Proteose-peptone-induced intraperitoneal neutrophils from rats were activated in terms of tumor cytotoxicity by pretreatment with culture supernatants from a human T cell leukemia line, Jurkat (culture sup). Culture sup-treated neutrophils showed cytotoxicity against various tumor cell lines. The cytotoxicity of culture sup-treated neutrophils was dependent on the number of neutrophils and the concentration of culture sup. Cytostasis by activated neutrophils was observed very early in the assay incubation period (within 6hr), but cytolysis first occurred at 24hr after the start of incubation. Factor(s) in culture sup responsible for the activation of cytotoxic neutrophils were stable to temperature and pH treatments, and their molecular weight was higher than 10, 000. The responsible factor(s) for activation of cytotoxic neutrophils were different from interleukin-2, serum-derived factor, and bacterial lipopolysaccharide.

View full abstract

The content of macrophage colony-forming cells (M-CFC) and the serum colony-stimulating activity (CSA) were investigated in mice after intravenous administration of Lactobacillus casei YIT9018 (LC9018). In normal BALB/c mice, 500μg of LC9018 increased both femoral and splenic M-CFC; the highest levels were found a few days and a week, respectively, after the administration. LC9018 also induced an increase in splenic M-CFC in C3H/HeJ mice as well as in C3H/HeN mice, unlike lipopolysaccharide (LPS), which was ineffective in C3H/HeJ mice. In Meth A-bearing BALB/c mice, LC9018 (250μg×5) suppressed the growth of tumor cells and increased femoral and splenic M-CFC to much greater extents than Lactobacillus plantarum YIT0102 (250μg×5) did. LC9018 induced a rise of serum granulocyte-macrophage CSA in the same way as LPS. Sera taken 6hr after LPS administration, when transferred to normal mice, induced increases in femoral and splenic M-CFC. However, sera taken 6hr after LC9018 administration increased neither femoral nor splenic M-CFC. These results indicate that LC9018 modulates myelopoiesis at least at the stage of the proliferation of M-CFC in a different way from LPS, and this ability may be related to its antitumor activity.

View full abstract

The roles of killer-helper factor (KHF) and accessory cells bearing I-region associated antigen (Ia) in the generation of cytotoxic T lymphocytes (CTL) were analyzed. Peanut agglutinin-binding (PNA⁺) thymocytes from C3H/HeN mice generated efficient CTL responses against 2, 4, 6-trinitrophenyl(TNP)-modified syngeneic spleen cells in the presence of cell-free supernatant (CFS) derived from purified protein derivatives(PPD)-stimulated Mycobacterium tuberculosis-primed BALB/c spleen cell culture (PPD-CFS). The KHF which is present in PPD-CFS devoid of the activities of IL-1 or IL-2 was required in conjunction with IL-2 for generation of CTL in PNA⁺ thymocytes. In contrast, PNA^- thymocytes as well as spleen cells could generate CTL in the absence of helper factors. However, a significant CTL response against Ia-negative syngeneic tumor cells was not induced from either PNA⁺, PNA^- thymocytes or spleen cells in the absence of Ia-positive accessory cells. Moreover, the treatment of spleen cells with relevant anti-Ia antiserum plus complement before TNP-modification abrogated the stimulatory capacity of TNP-spleen cells. In both cases, the addition of Ia-positive accessory cells restored the impaired capacity of TNP-modified stimulator cells. The addition of IL-1 to the culture of PNA^- thymocytes or spleen cells stimulated with TNP-X5563 cells in the absence of accessory cells restored the CTL generation. In contrast, the addition of IL-1 to the culture of PNA⁺ thymocytes was ineffective. The role of Ia-positive accessory cells in the generation of CTL in a subpopulation of thymocytes is discussed.

View full abstract

The B lymphocytes from pleural effusion of a gastric cancer patient were fused with murine myeloma cells (X63-Ag8.653). Thirty-four out of 62 clones were found to secrete human monoclonal antibodies (23 IgGs and 11 IgMs) by means of enzyme-linked immunosorbent assay. Fourteen monoclonal antibodies were tested for histological reactivity with cancer and normal tissues by immunoperoxidase staining. Among them, two monoclonal antibodies reacted rather specifically with gastrointestinal cancerous tissues. The human monoclonal antibody (HMoAb) 3B7 (IgG) reacted strongly with 4 out of 5 gastric carcinoma tissues and 2 out of 5 colonic carcinoma tissues, but did not react with non-cancerous tissues (stomach, colon, liver, pancreas and lung). In addition, HMoAb 3B7 reacted heterogeneously with autologous gastric carcinoma tissue sections. The hybridoma 3B7 has continued producing human monoclonal antibody for 12 months after fusion. By chromosomal analysis, it was shown that hybridoma 3B7 retains both human and mouse chromosomes. HMoAb 3B7 may be useful for research on tumor-associated antigens and therapeutic techniques.

View full abstract