PubMed · 4283947
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G B Pliss. Carcinogenic properties of benzidine.. https://pubmed.ncbi.nlm.nih.gov/4283947/
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The G12 subfamily of heterotrimeric G proteins, comprised of the alpha-subunits Galpha12 and Galpha13, has been implicated as a signaling component in cellular processes ranging from cytoskeletal changes to cell growth and oncogenesis. In an attempt to elucidate specific roles of this subfamily in cell regulation, we sought to identify molecular targets of Galpha12. Here we show a specific interaction between the G12 subfamily and the cytoplasmic tails of several members of the cadherin family of cell-surface adhesion proteins. Galpha12 or Galpha13 binding causes dissociation of the transcriptional activator beta-catenin from cadherins. Furthermore, in cells lacking the adenomatous polyposis coli protein required for beta-catenin degradation, expression of mutationally activated Galpha12 or Galpha13 causes an increase in beta-catenin-mediated transcriptional activation. These findings provide a potential molecular mechanism for the previously reported cellular transforming ability of the G12 subfamily and reveal a link between heterotrimeric G proteins and cellular processes controlling growth and differentiation.
We studied ganglioside expression in 12 human metastatic brain tumors metastasized from colon (4), renal (3), lung (2), esophagus (1), pancreas (1), and mammary (1) carcinomas. GM3 was the major common ganglioside expressed in brain metastatic tumor tissues, and GT1b was also present in all the metastatic brain tumor tissues. The latter was identified by TLC-immunostaining and characterized structurally by secondary ion mass spectrometry combined with 'Far-Eastern blot'. The immunohistochemical analysis of frozen tissue sections confirmed localization of GT1b in the tumor cell membrane or cytosol. GT1b was shown to be expressed both in the primary colon carcinoma and the metastasis of a single patient by immunohistochemical procedure. In systemic carcinomas without brain metastasis, GM3 was a common major component, but no GT1b was detected. These findings indicate that GT1b is a brain metastasis-associated ganglioside. We speculate that the presence of GT1b would be a useful marker for estimating metastatic potentials to the brain.
BACKGROUND: Infection with human papillomavirus (HPV) type 16 has been implicated as a risk factor for esophageal squamous cell carcinoma in three seroepidemiologic studies. We conducted a larger, population-based study to verify this association and to investigate possible confounding factors. METHODS: We performed a nationwide case-control study in Sweden of HPV16 or HPV18 infection and risk of esophageal squamous cell carcinoma or esophageal/gastroesophageal adenocarcinoma. Tumors were strictly classified by their location and histologic type. Case subjects with incident cancers and population-based control subjects donated blood samples and were interviewed in person about potential confounding factors. An enzyme-linked immunosorbent assay was used to detect HPV seropositivity. Multivariate analyses were conducted to study relationships between HPV seropositivity, level of education, smoking (all tobacco) status, alcohol consumption, and cancer risk. RESULTS: We compared 121 case subjects with esophageal squamous cell carcinoma and 173 case subjects with adenocarcinoma of the esophagus or gastroesophageal junction with 302 population-based control subjects. The age- and sex-adjusted odds ratios (ORs) for squamous cell carcinoma were 1.0 (95% confidence interval [CI] = 0.5-2.0) for persons seropositive for HPV16 and 0.5 (95% CI = 0.2-1.1) for persons seropositive for HPV18 in comparison with seronegative individuals. The corresponding ORs for adenocarcinoma were 1.2 (95% CI = 0.7-2.2) and 0.2 (95% CI = 0.1-0.7), respectively. Adjustments for smoking status, alcohol consumption, and level of education did not alter the results. CONCLUSIONS: We found no evidence of a positive association between HPV16 or HPV18 infection and either form of esophageal cancer. Our results do not support conclusions from previous studies.