Mitochondrial Function Differences between Tumor Tissue of Human Metastatic and Premetastatic CRC.

Most colorectal cancer (CRC) patients die as a consequence of metastasis. Mitochondrial dysfunction could enhance cancer development and metastatic progression. We aimed to evaluate the adaptations associated with mitochondrial function in tumor tissues from stages III and IV of human CRC and whether they could ultimately be used as a therapeutic target in metastatic colorectal cancer (mCRC). We analyzed the protein levels by Western blotting and the enzymatic activities of proteins involved in mitochondrial function, as well as the amount of mitochondrial DNA (mtDNA), by real-time PCR, analyzing samples of non-tumor adjacent tissue and tumor tissue from stages III and IV CRC patients without radio- or chemotherapy treatment prior to surgery. Our data indicate that the tumor tissue of pre-metastatic stage III CRC exhibited an oxidant metabolic profile very similar to the samples of non-tumor adjacent tissue of both stages. Notable differences in the protein expression levels of ATPase, IDH2, LDHA, and SIRT1, as well as mtDNA amount, were detected between the samples of non-tumor adjacent tissue and tumor tissue from metastatic CRC patients. These findings suggest a shift in the oxidative metabolic profile that takes place in the tumor tissue once the metastatic stage has been reached. Tumor tissue oxidative metabolism contributes to promote and maintain the metastatic phenotype, with evidence of mitochondrial function impairment in stage IV tumor tissue.

Mutant p53 induces SIRT3/MnSOD axis to moderate ROS production in melanoma cells.

The TP53 tumor suppressor gene is the most frequently altered gene in tumors and mutant p53 isoforms can acquire oncogenic properties referred to as gain-of-function (GOF). In this study, we used wild-type (A375) and mutant p53 (MeWo) melanoma cell lines to assess the regulation of the mitochondrial antioxidant manganese superoxide dismutase (MnSOD) by mutant p53. The effects of mutant p53 were evaluated by qPCR, immunoblotting, enzyme activity assay, cell proliferation assay, reactive oxygen species (ROS) assay after cellular transfection. We demonstrate that mutant p53 induces MnSOD expression, which is recovered by the ROS scavenger N-acetyl-l-cysteine. This suggests MnSOD induction as a defense mechanism of melanoma cells to counterbalance the pro-oxidant conditions induced by mutant p53. We also demonstrate that mutant p53 induces the expression of Sirtuin3 (SIRT3), a major mitochondrial NAD+-dependent deacetylase, stimulating MnSOD deacetylation and enzymatic activity. Indeed, the restoration of SIRT3 reverses MnSOD activity decrease by mutant p53 knock-down. Finally, MnSOD knock-down further enhances mutant p53-mediated ROS increase, counteracting mutp53-dependent cell hyperproliferation. This indicates that SIRT3 and MnSOD act to maintain ROS levels controlled to promote cell proliferation and survival, providing new therapeutic opportunities to be further considered for clinical studies in cancer patients bearing mutant TP53 gene.

Non-tumor adjacent tissue of advanced stage from CRC shows activated antioxidant response.

Colorectal cancer (CRC) is a leading cause of malignant cancer-related morbidity and mortality, with a higher incidence in developed countries and a high mortality rate mainly attributable to metastases. The aim of the present study was to determine the metabolic adaptations related to oxidative stress in tumor tissue from advanced stages (III and IV) of CRC and whether they could be used as potential biomarkers for clinical applications. To tackle this aim, we have analyzed the protein expression levels related to oxidative stress and the enzymatic activities of MnSOD and catalase, comparing samples of non-tumor adjacent tissue and tumor tissue of CRC patients in stages III and IV. The results showed no differences between stage III and IV in tumor tissues for any of the proteins studied. However, some differences were found between samples of non-tumor adjacent tissue and tumor tissue for some of the antioxidant enzymes. Overwhelmingly, the greatest differences were detected when comparing samples of non-tumor adjacent tissue from stage III and stage IV. To the best of our knowledge, this is the first study where differences between the non-tumor adjacent tissues of CRC patients from different cancer stages were determined. This study suggests that the parameters analyzed should be evaluated as biomarkers for the evolution of CRC. Furthermore, tumor tissue status should not be of sole importance for the prognosis of CRC, as the non-tumor adjacent tissues could also merit consideration.

Initial activation status of the antioxidant response determines sensitivity to carboplatin/paclitaxel treatment of ovarian cancer.

BACKGROUND/AIM: Ovarian carcinoma is the main cause of gynecological cancer related deaths. The aim of this study was to determine the activation status of the antioxidant response in samples of ovarian serous carcinoma from paraffin-embedded biopsies and compare them with the response of patients to carboplatin-paclitaxel treatment. MATERIALS AND METHODS: Estrogen receptor alpha (ERα), antioxidant enzymes, and uncoupling protein (UCP) levels were analyzed by western blotting and the presence of estrogen receptor beta (ERß) was investigated by immunohistochemistry (IHC). RESULTS: Lower levels of ERα, antioxidant enzymes and UCPs were found in patients resistant to treatment in comparison to the carboplatin/paclitaxel-sensitive ones; IHC revealed a greater presence of ERß in sensitive patients. CONCLUSION: These results indicate that patients resistant to treatment have a lower level of antioxidant response activation compared to sensitive patients, fact which may be related to the efficacy of this treatment.