Protein A-activated macrophages induce apoptosis in Ehrlich's ascites carcinoma through a nitric oxide-dependent pathway.
Protein A (PA) of Staphylococcus aureus has been demonstrated to possess anti-tumor activity against a wide variety of tumors. In the current study we endeavored to obtain a mechanistic insight into PA-mediated Ehrlich's ascites carcinoma (EAC) killing. Our results indicate that PA stimulates generation of nitric oxide (NO) from murine peritoneal macrophages. Nitric oxide in turn induces cytotoxic damage to the tumor cells. Analysis of the morphological features and cell cycle phase distribution pattern of nuclear DNA revealed an induction of apoptosis (appearance of sub-G0/G1 population) in EAC after PA treatment. We have further elaborated the alterations in the expressions of the proto-oncoproteins p53 and Bax, together with a change in the ratio of Bcl-2/Bax in the treated tumor cells, which favor apoptosis. PA-induced apoptosis and changes in the expression of oncoproteins in the tumor cells was prevented by the suppression of NO release by the addition of L-NAME, the competitive NOS inhibitor, suggesting a possible mechanism by which PA exerts its anti-tumor activities involving nitric oxide through the alteration in the expressions of pro-apoptotic proteins.
Chattopadhyay
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Animal Physiology Section, Bose Institute, P-1/12 CIT Scheme VII M, Calcutta 700 054, India.
Das
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D000818:Animals; D017209:Apoptosis; D002286:Carcinoma, Ehrlich Tumor / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects; D004247:DNA / Q000032:analysis; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D017737:Macrophages, Peritoneal / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism; D008297:Male; D051379:Mice; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000097:blood / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013205:Staphylococcal Protein A / Q000276:immunology* / Q000494:pharmacology / Q000627:therapeutic use / Q000633:toxicity; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051028:bcl-2-Associated X Protein
C494827:Bax protein, mouse; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D013205:Staphylococcal Protein A; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D009569:Nitric Oxide; D004247:DNA; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D019331:NG-Nitroarginine Methyl Ester