Oncogenic mutation or overexpression of oncogenic KRAS or BRAF is not sufficient to confer oncogene addiction.

Oncogene addiction is a cellular property by which cancer cells become highly dependent on the expression of oncogenes for their survival. Oncogene addiction can be exploited to design molecularly targeted drugs that kill only cancer cells by inhibiting the specific oncogenes. Genes and cell lines exhibiting oncogene addiction, as well as the mechanisms by which cell death is induced when addicted oncogenes are suppressed, have been extensively studied. However, it is still not fully understood how oncogene addiction is acquired in cancer cells. Here, we take a synthetic biology approach to investigate whether oncogenic mutation or oncogene expression suffices to confer the property of oncogene addiction to cancer cells. We employed human mammary epithelium-derived MCF-10A cells expressing the oncogenic KRAS or BRAF. MCF-10A cells harboring an oncogenic mutation in a single-allele of KRAS or BRAF showed weak transformation activity, but no characteristics of oncogene addiction. MCF-10A cells overexpressing oncogenic KRAS demonstrated the transformation activity, but MCF-10A cells overexpressing oncogenic BRAF did not. Neither cell line exhibited any oncogene addiction properties. These results indicate that the introduction of oncogenic mutation or the overexpression of oncogenes is not sufficient for cells to acquire oncogene addiction, and that oncogene addiction is not associated with transformation activity.

Correlation between synthesis of α2-macroglobulin as acute phase protein and degree of hepatopathy in rats.

The degree of hepatopathy affecting the synthesis of α2-macroglobulin (α2M) as an acute phase protein in rats was investigated. Hepatopathy was induced in Sprague-Dawley rats by intravenous administration of galactosamine at a dose of 30 mg/kg for 7 days. Inflammation was induced by intramuscular injection of turpentine oil at a dose of 2 mL/kg. Blood was collected before turpentine oil injection and at 24, 48, 72 and 96 h after injection. Serum concentrations of α2M were measured by enzyme-linked immunosorbent assay. Mean values of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in rats administered galactosamine were significantly higher than in controls. Mean values of body weight and total protein were significantly lower than in controls. Serum concentrations of α2M in the galactosamine group were significantly lower than in controls. Kinetic parameters, area under the concentration-time curve (AUC0-96) and maximum serum concentration (Cmax), were significantly lower than in controls. The cut-off value for detecting the effects on synthesis of α2M in liver was 46.9 mgˑh/mL. Seven rats (77.8%) were assessed for decreases in the synthesis of α2M due to hepatopathy. Two rats showed no influence on the synthesis of α2M, despite administration of galactosamine. AST and ALT in these two rats were ≤ 285 and ≤ 174 U/L, respectively. In conclusion, synthesis of α2M in rats is evidently suppressed in the severe stages of hepatopathy.