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Purpose: Oxidative stress has impacts on the KRas and Nrf2/Keap1 pathways, which have multiple interactions with each other and play important roles in colorectal cancer (CRC). This study investigated the expressions of proteins in the KRas and Nrf2/Keap1 pathways and their associations with clinicopathological features in CRC., Methods: The protein levels of Nrf2, Keap1, Bach1, p62, HO1, KRas, Erk, Raf1 and PI3K in both the tumour and normal tissues of 60 CRC subjects were determined by Western blot and their T/N (tumour/normal tissue) ratios were correlated with clinicopathological features., Results: The T/N ratios of proteins in the KRas and Nrf2/Keap1 pathways had correlation patterns and proximity profiles in cluster dendrograms different in CRC with different status of lymphovascular invasion (LVI) or lymph node/distant metastases. The Keap1 protein T/N ratio was a significant predictor (odd ratio: 2.24; 95% confidence interval: 1.26 - 4.38) of LVI, which in turn predicted metastases (11.0; 3.49 - 39.8)., Conclusion: The interactions between the KRas and Nrf2/Keap1 pathways may be affected differently by LVI and metastases, and the protein T/N ratio of Keap1 may be helpful for predicting LVI in CRC.

Introduction: The Nrf2 (nuclear factor erythroid 2-like 2; NFE2L2)/Keap1 (Kelch-like ECH-associated protein 1) pathway and the TXN (thioredoxin)/GSH (glutathione) system interact mutually and regulate cellular redox with impacts on cancer metastasis and S-glutathionylation of protein, which is an indicator of cell distress. This study investigates the levels of proteins in the Nrf2/Keap1 pathway and the TXN/GSH system and SGP (S-glutathionylated protein) in CRC (colorectal cancer) with or without metastasis., Materials and Methods: The protein levels of Nrf2, Keap1, Bach1 (BTB domain and CNC homolog 1), TXN, TXNRD1 (thioredoxin reductase 1), GSR (glutathione reductase) and SGP with molecular weight 31-172 kDa in the normal and tumour tissues of 64 CRC subjects were determined by Western blot., Results: The protein levels and their T/N (tumour/normal tissue) ratios of the Nrf2/Keap1 pathway, the TXN/GSH system and SGP were correlated to different extents in the tissues of CRC subjects with or without lymph node/distant metastasis. The T/N ratios of SGP (odd ratio: 0.19; 95% CI: 0.04-0.74) and lympho-vascular invasion (4.2; 1.39-13.73) were significant predictors for metastasis., Conclusions: SGPs have protein levels correlated with those of the Nrf2/Keap1 pathway and their T/N ratios are a negative predictor for metastasis in CRC.

Background: Both mitochondria and the Nrf2/Keap1 pathway are targets of cancer therapy. Reactive oxygen species released from mitochondria can activate Nrf2, and the Nrf2/Keap1 pathway affects glycolysis, oxidative phosphorylation, mitochondrial biogenesis and mitophagy., Objective: This study investigates the associations between the expressions of proteins in the Nrf2/Keap1 pathway and those related to mitochondrial function and glycolysis in colorectal cancer (CRC) with or without metastasis., Methods: The protein levels of HO1, Nrf2, Keap1, Bach1, p21, p62, NRF1, LC3, ATP5B, HSP60 and GAPDH in the normal and tumor tissues of 60 CRC subjects were determined by Western blot., Results: The Keap1 protein levels, the ATP5B/HSP60 ratio and the BEC index were higher in the tumor than in the normal tissues of CRC with or without metastasis. The following clusters were found in the dendrogram: Nrf2 and p21 with ATP5B and GADPH in all the tissues and with NRF1 in all except the tumor tissues with metastasis; Bach1 with ATP5B and GAPDH in the tumor tissues; Keap1 with p62 in all the tissues, with LC3 in the tumor tissues and with NRF1 and HO1 in the tumor tissues with metastasis., Conclusions: Nrf2, Keap1, Bach1 and p21 have the association with the proteins related to mitochondrial functions different among the tissues of CRC with or without metastasis.

Heme oxygenase 1 (Hmox1) plays an important role in the growth and spread of tumor, and its expression is regulated positively by Nrf2 [nuclear factor (erythroid-derived 2)-like 2; NFE2L2] and negatively by kelch-like ECH-associated protein 1 (Keap1) and by BTB and CNC homology 1 (Bach1). Both Hmox1 and Nrf2 contribute to distant metastasis of cancer. The mRNA levels of Hmox1, Nrf2, Keap1, and Bach1 in the tumor and normal tissues of 84 subjects with colorectal cancer (CRC) were determined by real-time polymerase chain reaction. The tumor had lower Hmox1 but higher Bach1 mRNA levels than the normal tissue. The correlations of Hmox1 with components of the Nrf2 pathway were not significant in the tumor tissue of CRC subjects with distant metastasis. The ratio of Hmox1/Nrf2 mRNA level (by percentage) in the tumor tissue was lower in the subjects with distant metastasis (97.4% (84.4-111.1%)) than in those without (101.0% (92.7-136.5%)) and was a predictor for distant metastasis in CRC (odds ratio: 0.83; 95% confidence interval: 0.68-0.97) along with serum carcinoembryonic antigen (1.0027, 1.006-1.064). The mRNA level of Hmox1 in the tumor tissue of CRC is not correlated with that of the Nrf2 pathway molecules, and its ratio to the Nrf2 level may be useful for suggesting distant metastasis in CRC., Competing Interests: The authors declare that they have no competing interests.

Oxidative stress is a contributing factor in the carcinogenesis of colorectal cancer. The Nrf2 [nuclear factor (erythroid-derived 2)-like 2; NFE2L2] pathway is one of the major cellular defense mechanisms against oxidative stress. This study investigated the expression of the Nrf2 pathway in colorectal cancer. Formalin-fixed paraffin-embedded tissue arrays consisting of the tumor, adjacent normal, and distant normal tissues from the resected specimens of 83 colorectal cancer patients were subjected to immunohistochemical (IHC) staining with antibodies against Nrf2, kelch-like ECH-associated protein 1 (Keap1), p21, P62, Parkinson protein 7 (Park7), prohibitin, BTB and CNC homology 1 (Bach1), CD34 and 8-hydroxy-2'-deoxyguanosine (8-OHdG). The mean IHC density of each IHC staining was digitally analyzed. The results showed that molecules of the Nrf2 pathway were actively expressed, with different expression profiles among the tumor and normal tissues. The oxidative stress, represented by the mean IHC staining density of 8-OHdG, did not differ but was correlated with the expressions of different Nrf2 pathway molecules to a varied extent in tumor and normal tissues of colorectal cancer. Keap1 [estimate, 0.49; 95% confidence interval (CI), 0.19-0.79] and Bach1 (estimate, 0.24; 95% CI, 0.11-0.38) were significant predictors for the expression of 8-OHdG and had the closest proximity to Nrf2 in the cluster dendrogram of the tumor and distant normal tissues, respectively. Advanced stage (estimate, 14.9; 95% CI, 2.99-26.8) and current smoker (estimate, 15.6; 95% CI, 1.92-29.3) were significant predictors with high estimates for Bach1 in the adjacent and distant normal tissues, respectively. In colorectal cancer, the molecules of the Nrf2 pathway have different expression profiles and a difference in their importance, especially Keap1 and Bach1, related to Nrf2 and oxidative stress among tumor and normal tissues.