Discussion It has been shown that HO-1 is an inducible enzyme, whose expression is often increased by those oxidative stresses, which produce reactive oxygen
species.3,14 In spite of the cytoprotective affects of HO-1 on healthy tissues following their exposure to harmful stimuli, it can also protect tumor cells. Such a protection can result in the progression Inhibitors,research,lifescience,medical of the disease. Different studies have shown that higher levels of HO-1 expression are associated with faster growth of tumors, as indicated by bigger volumes of nodules or by more numerous cancer cells.11,15 Although some studies have reported a selective decrease in the expression of HO-1 in a few malignant cells such as adenocarcinoma or tongue squamous carcinoma, most studies have shown that the expression of HO-1 is strongly up-regulated in various tumors. Therefore, it seems that HO-1 represent a molecular target in some cancers. The current Inhibitors,research,lifescience,medical study was designed to determine the expression pattern of HO-1 gene in five cancer cell lines that are highly prevalent in . Until now, only limited data are available on the expression of HO-1 in the cell lines investigated here. Among Inhibitors,research,lifescience,medical the cell line studied, HEPG2 cell line showed the highest expression of HO-1 based on the level of mRNA measured. The increased
expression of HO-1 mRNA in HEPG2 cell line in the present study is in agreement with the high levels of expression of HO-1 in tissues of hepatocellular carcinoma described by Doi and colleagues.16 Thus, based on these results, we suggest HEPG2 cell line is the best model for future analysis Inhibitors,research,lifescience,medical of biology and regulation of HO-1 in hepatocellular carcinoma cell lines. The gene of HO-1 was found by RT-PCR to be expressed in MCF7 cell line as well as in A549 cell line. Human lung adenocarcinoma A549 cells constitutively express HO-1, which help them to resist against toxic compounds Inhibitors,research,lifescience,medical and antitumor drugs.17 Concerning MCF7, our results are in line with the results obtained by Hill et al. who reported overexpression
of HO-1 protein in MCF-7 cells.18 A moderate level of HO-1 expression could be observed in myeloid leukemia-derived cell line K562. Given the up-regulation of HO-1 expression in myeloid leukemia cell line and based on the function of HO-1 as a survival factor in chronic myeloid leukemia,19 it can be suggested that there is an authentic Dacomitinib pattern of HO-1 expression related to chronic myeloid leukemia. Based on our results the LS174T cell line was the only one amongst the investigated cancer cell lines to reveal no HO-1 expression. In contrast to our results, Fang and co-workers indicated that up-regulation of HO-1 expression in colon cancer was a main factor for resistance against anticancer therapy, since the HO-1 inhibitors or targeted knocking down of the HO-1 expression made the cultured tumor cell lines much more sensitive to anticancer therapy.20 This discrepancy could be due to difference in the colon cell lines.