Detection and quantification of poly-ADP-ribosylated cellular proteins of spleen and liver tissues of mice in vivo by slot and Western blot immunoprobing using polyclonal antibody against mouse ADP-ribose polymer

Altered BRCA1 and BRCA2 responses and mutation of BRCA1 gene in mice exposed chronically and transgenerationally to aqueous extract of betel nut (AEBN)

The Brca1 and Brca2 tumor suppressor genes are involved in the maintenance of genomic integrity as they facilitate error free DNA repair. This study was designed to understand the role of Brca1 and Brca2 in betel nut (BN) induced chronic and transgenerational carcinogenesis in mice. Young male and female Swiss Albino mice were chronically as well as transgenerationally exposed to aqueous extract of betel nut (AEBN) in drinking water (2 mg ml(-1)) for up to 24 weeks. In chronically exposed mice, the levels of Brca1 and Brca2 proteins were elevated to approximately 1.4-fold over the age matched controls after 2 weeks of exposure to AEBN, followed by a decline below the controls. In transgenerationally exposed mice, both Brca1 and Brca2 proteins remained below the controls from the onset of AEBN exposure and rapidly declined further, indicating a loss of tumor suppressor protection. Nucleotide sequencing of exon 11 of Brca1 and exon 27 of Brca2 did not reveal mutation in liver nodules of chronically exposed mice, while a G → C mutation Brca1 was observed in liver nodules as well as in solid tumors developing in transgenerationally exposed mice. Thus, the genomic instability arising due to the lowering in the levels of Brca1 and Brca2 proteins and mutation in exon 11 of Brca1 gene contributed to the increased risk of cancer in mice exposed transgenerationally to AEBN.

ADP-ribose polymer--a novel and general biomarker of human cancers of head & neck, breast, and cervix

Background

Poly-ADP-ribosylation, a reversible post-translational modification of primarily chromosomal proteins, is involved in various cellular and molecular processes including carcinogenesis. ADP-ribose polymer or poly-ADP-ribose adducts are enzymatically added onto or stripped off the target chromosomal proteins during this metabolic process. Due to this, the chromatin superstructure is reversibly altered, which significantly influences the pattern of gene expression. We hypothesize that a decrease in the concentration of total poly-ADP-ribose adducts of peripheral blood lymphocyte (PBL) proteins strongly correlates with the incidence of human cancer.

Results

Using a novel immunoprobe assay, we show a statistically significant (P ≤ 0.001) reduction (~ 42 to 49%) in the level of poly-ADP-ribose adducts of PBL proteins of patients with advanced cancers of head & neck (H & N) region (comprising fourteen distinct cancers at different sites), breast and cervix in comparison to healthy controls.

Conclusions

These findings imply potential utility of the poly-ADP-ribose adducts of PBL proteins as a novel and general biomarker of human cancers with potentials of significant clinical and epidemiological applications.

Altered p53 response and enhanced transgenerational transmission of carcinogenic risk upon exposure of mice to betel nut

Alteration of p53 protein level, and possible mutation of the p53 gene during carcinogenesis in mice exposed chronically (P) and transgenerationally to 2mg/ml aqueous extract of betel nut (AEBN) in drinking water, were studied. Exons 5 and 7 of the p53 gene were not mutated under both chronic and transgenerational exposure, but, p53 protein response was altered. In P mice, p53 protein was initially upregulated in comparison to age-matched controls, reaching 2.5 folds in the liver after 6 weeks of exposure. Subsequently, p53 protein declined to control level after 16 weeks, with concomitant preneoplastic nodulation of the liver. After 24 weeks, p53 protein was below control level, and preneoplastic nodules were well-developed. The level of p53 protein in transgenerationally exposed mice remained invariant in comparison to age-matched controls. Liver nodulation was significantly advanced, developing in F1 mice after 8 weeks, F2 mice after 6 weeks and F3 mice after 4 weeks of exposure. Anomalies not observed in P mice, developed in transgenerationally exposed mice, albeit, non-significantly. Thus, AEBN exposure enhanced transgeneration transmission of carcinogenic risk.

In vivo exposure of swiss albino mice to chronic low dose of dimethylnitrosamine (DMN) lowers poly-ADP-ribosylation (PAR) of bone marrow cell and blood lymphocyte proteins

Efforts to identify an easy and convenient biomarker of carcinogenesis with potentials of application in mass screening program continue. In a series of investigations on mice exposed to different carcinogens, poly-ADP-ribosylation (PAR) of cellular proteins of different tissues has been shown to be a potential biomarker of carcinogenesis. Because blood based biomarker of carcinogenesis offers significant advantage in its use in a cancer screening program, this investigation was undertaken to find correlations between initiation of carcinogenesis and PAR of bone marrow cell (BMC) and blood lymphocyte (BL) proteins in mice chronically exposed to low dose of dimethylnitrosamine (DMN) for up to four weeks in vivo. The exposure was either alone or in combination with 3-aminobenzamide (3-AB), an inhibitor of PAR. Total PAR of cellular proteins and of histone H1 protein were monitored by slot and Western blot immunoprobe assays, respectively. The PAR of total cellular proteins as well as of histone H1 was down-regulated in duration of exposure dependent manners. The results suggest that BMC and BL mirrored status of PAR in other tissues. This finding opens up the possibility of using PAR as a biomarker of carcinogenesis in a blood based test utilizing immunoprobe assay of cellular PAR.

Progressive reduction in poly-ADP-ribosylation of histone proteins during Dalton's lymphoma induced ascites tumorigenesis in mice

Poly-ADP-ribosylation (PAR) reaction, which primarily modifies histone proteins, is postulated to have decisive influence in carcinogenesis. Therefore, it has been suggested as a biomarker of carcinogenesis. Dalton's lymphoma induced ascites tumorigenesis in mice provides a convenient model to study PAR of histone proteins during late stage of cancer development. Using a Western blot immunoprobe assay of cellular PAR, this report shows that PAR of liver and spleen histone proteins was progressively and significantly reduced during Dalton's lymphoma induced ascites tumorigenesis in mice. Implication of the findings in early detection of cancer has been discussed.