Selective elimination of younger erythrocytes in blood circulation and associated molecular changes in benzo (a) pyrene induced mouse model of lung cancer.

Background: Anemia is a common feature in cancer patients. The present research was conducted to explore the mechanisms of induction of anemia in a mouse model of lung cancer.

Methods: The lung cancer was induced by treating orally with BaP (50 mg/kg body weight, twice a week for four weeks). The erythrocyte kinetics were studied using a double in vivo biotinylation (DIB) technique. ROS production and apoptosis analysis were done by staining with the CMH2DCFDA stain and anti-mouse Annexin V antibody, followed by flow cytometry. The expression of antioxidant, apoptotic, anti-apoptotic and inflammatory genes was analyzed by quantitative PCR (RT-qPCR).

Results: BaP-induced tumour reduced body weight and induced persistent haemolytic anaemia. The kinetics data suggest that, though reticulocyte production was enhanced, the proportion of young erythrocytes did not increase in the same proportion. The young aged erythrocytes were selectively eliminated from blood circulation, but intermediate and old aged erythrocytes persisted for a longer duration. The tumour progression leads to a significant increase in ROS production and apoptosis in the erythrocytes. The molecular data suggests that the expression levels of antioxidants (SOD1, catalase, and GPX1) and erythropoietin (Epo) were significantly increased. The anti-inflammatory genes Interleukin-6 (IL-6), Interleukin-10 (IL-10) were significantly decreased.Apoptotic genes Bax, and caspase 3 were significantly decreased while Bcl 2 was significantly increased in the blood of tumour-bearing mice.

Conclusions: The overall data suggest that erythrocyte turnover is severely modulated with the progression of tumor. The apoptosis, ROS levels, antioxidant, anti-apoptotic, and Epo gene expressions were increased, but proapoptotic and anti-inflammatory gene expression were suppressed.