Aldehyde dehydrogenase has been characterized as a cancer st

Aldehyde dehydrogenase has been characterized as a cancer stem cell marker, which plays a key role in various biological processes in tumor, including cell proliferation, invasiveness and chemoresistance. Recent data of Abourbih et al reported that ALDH1 expression did not correlate with primary tumor grade, stage or with the clinical outcome but ALDH1 membrane expression was significantly higher in low stage as compared to high stage of RCC tumors. Interesting is also that metastatic tumors expressed significantly lower amounts of ALDH1 than primary tumors [21]. During disease progression and metastasis, tumor insulin receptor inhibitor lose the expression patterns of the normal epithelium from which they originate, and therefore healthy kidney has been shown to express large amounts of ALDH1. This confirm that metastases may form altered pathways than the primary tumors, which would clarify differences in enzymes expression [21]. In our previous study we found that the total activity of aldehyde dehydrogenase in cancer cells of RCC is at the same level as in normal renal tissue [10]. These findings are similar to our results in serum patients with renal cancer. There is no significant difference between ALDH activity in serum cancer patients and healthy controls. We also found that renal cell cancer patients have significantly higher total activity of alcohol dehydrogenase and its class I isoenzyme in the serum. But proteomic analysis conducted by Sun et al provide that ADH protein is down regulated in clear cell RCC compared with corresponding normal kidney tissue [6]. One possible explanation for increased ADH activity could be that with disease progression, tumor cells lose the expression patterns of the normal epithelium from which they originate. Moreover differences in ADH and ALDH activity between cancer cells and healthy tissue may be one of the factors intensifying carcinogenesis. Increase in ADH activity with normal ALDH activity suggests that cancer cells have a greater capability for ethanol oxidation and less ability to remove acetaldehyde. Numerous experiments have shown that acetaldehyde has direct mutagenic and carcinogenic effect because of interferes with DNA synthesis and repair and forms of stable adducts [22]. Many recent data revealed that kidney alcohol dehydrogenase activity increased significantly after ethanol administration what affected the capacity of the kidney to prevent NADH accumulation in the cytosol. The kidney was not able to balance the NADH excess even though an increase in malate dehydrogenase, lactate dehydrogenase, aspartate and alanine transaminase activities was noted [23]. Moreover, after long-term ethanol consumption kidney reduce decreasing glutathione/oxidized glutathione ratio, what indicate oxidative stress [24]. These results showed specific changes in kidney antioxidant system and glutathione status as a consequence of long-term ethanol administration. Chronic ethanol consumption leads to induction of cytochrome P450 2E1 associated with an increased production of reactive oxygen species, which are an important factor in ethanol-related carcinogenesis. Cancer cells can also release isoenzymes to the serum, what can be helpful in malignant diagnosis. In our data, increase in ADH I activity can origin from the renal cancer cells. These findings are similar to studies of Jelski et al in gastrointestinal tract cancers. Liver and colorectum cancer cells exhibits increased activity of ADH I what is the reason of elevated activity of this isoenzyme in the serum of cancer patients. In esophagus and stomach neoplasma, cancer cells have increased activity of ADH IV and patients have elevated ADH IV activity in serum [7]. ADH and ALDH play a significant role in the metabolism of many biologically important substances, including retinoic acid (RA). ADH catalyzes the oxidation of retinol to retinal, which is converted to retinoic acid by ALDH. Enzyme, which especially plays a role in RA synthesis is ADH class I. In situ hybridization showed that class I ADH mRNA was localized in kidney, where significant retinoic acid levels were detected [25]. Retinoic acid is particularly essential because of its profound effects on cellular growth and differentiation. Depletion of systemic and tissue-specific retinoid acid may have consequences for cell proliferation, differentiation and possibly malignant transformation [26]. Disturbances between ADH and ALDH activities in cancer cells of renal cell carcinoma can lead to disorders in RA synthesis what can be a factor entangled in kidney carcinogenesis.