Pronounced tumour regression after radiotherapy is associated with negative/weak glucose transporter-1 expression in rectal cancer.

UNLABELLED: The aim of this study was to assess glucose transporter-1 (GLUT-1) expression as a predictor of disease outcome in rectal cancer treated by preoperative radio- or chemoradiotherapy. PATIENTS AND METHODS: Operative samples from 175 rectal cancer patients and 78 preoperative biopsies were analysed for GLUT-1 expression using immunohistochemistry. Forty-six patients received long-course radiotherapy, with/without chemotherapy and tumour regression grade was analysed in these specimens. RESULTS: Negative GLUT-1 expression was seen in 25/78 (32%) of the preoperative biopsies and in 38/78 (49%) of the operative samples. There was no significant correlation of GLUT-1 with common clinicopathological factors. A trend towards longer disease-free survival (DFS) for the long-course radiotherapy group patients was seen with negative/weak GLUT-1 staining intensity (p=0.066) and excellent tumour regression grade (p=0.068) in operative samples. Disease-free survival (p=0.068) and disease-specific survival (p=0.024) of the patients with excellent tumour regression were longer than among the patients with moderate or less regression. CONCLUSION: A trend towards longer DFS among patients in favour of negative/weak GLUT-1 staining in the operative samples after long-course radiotherapy is demonstrated.

Preoperative radiotherapy downregulates the nuclear expression of hypoxia-inducible factor-1alpha in rectal cancer.

OBJECTIVE: To assess the value of hypoxia-inducible factor-1alpha (HIF-1alpha) expression as a predictor of disease outcome in rectal cancer treated by preoperative radio- or chemoradiotherapy. MATERIAL AND METHODS: Operative samples from 168 rectal cancer patients and 79 respective preoperative biopsies were analyzed for nuclear HIF-1alpha protein expression using immunohistochemistry by three approaches: (a) positive/negative, (b) the percentage of HIF-positive cancer cells and (c) staining intensity. The patients had received either short- (n = 75) or long-course radiotherapy with or without chemotherapy (n = 39) or no treatment preoperatively (n = 54). RESULTS: HIF-1alpha staining was positive in 70% of the diagnostic biopsies but negative in most of the post-radiotherapy specimens (60%). HIF-1alpha expression in the biopsies was downregulated in 56% of samples taken after preoperative treatment, while negative HIF-1alpha expression was upregulated in 25% of samples. Patients who had HIF-negative tumours after long-course radiotherapy had significantly (P = 0.001) better disease-specific survival (DSS) in univariate analysis. In the multivariate (Cox) regression model, HIF-1alpha lost its significance and only being in the preoperative treatment group was an independent predictor of disease-free survival. In a similar Cox model, disease recurrence and the number of metastatic lymph nodes were independent predictors of DSS. CONCLUSIONS: HIF-1alpha expression was positive in most of the preoperative biopsies but downregulated in most of the operative samples, implicating that preoperative radiotherapy downregulates HIF-1alpha expression in rectal cancer. Negative HIF expression after preoperative long-course radiotherapy was associated with significantly better DSS.

Expression of carbonic anhydrase IX suggests poor outcome in rectal cancer.

The aim of the study is to assess the value of carbonic anhydrase isozyme IX (CA IX) expression as a predictor of disease-free survival (DFS) and disease-specific survival (DSS) in rectal cancer treated by preoperative radio- or chemoradiotherapy or surgery only. Archival tumour samples from 166 patients were analysed for CA IX expression by three different evaluations: positive/negative, proportion of positivity and staining intensity. The results of immunohistochemical analysis were confirmed by demonstrating CA IX protein in western blotting analysis. Forty-four percent of the operative samples were CA IX positive, of these 34% had weak and 66% moderate/strong staining intensity. In univariate survival analysis, intensity of CA IX expression was a predictor of DFS (P=0.003) and DSS (P=0.034), both being markedly longer in tumours with negative or weakly positive staining. In multivariate Cox model, number of metastatic lymph nodes and CA IX intensity were the only independent predictors of DFS. Carbonic anhydrase isozyme IX intensity was the only independent predictor of DSS, with HR=9.2 for dying of disease with moderate-intense CA IX expression as compared with CA IX-negative/weak cases. Negative/weak CA IX staining intensity is an independent predictor of longer DFS and DSS in rectal cancer.

Hypoxia-activated autophagy accelerates degradation of SQSTM1/p62.

Sequestosome 1 (SQSTM1/p62) is a multifunctional protein involved in signal transduction, protein degradation and cell transformation. Hypoxia is a common feature of solid tumours that promotes cancer progression. Here, we report that p62 is downregulated in hypoxia in carcinoma cells and that the expression is rapidly restored in response to reoxygenation. The hypoxic p62 downregulation did not occur at the mRNA level and was independent of the hypoxic signal mediators hypoxia-inducible factor (HIF) and von Hippel-Lindau tumour suppressor protein as well as the activity of HIF-prolyl hydroxylases and was not mediated by proteosomal destruction. Autophagy was activated in hypoxia and was required for p62 degradation. The hypoxic degradation of p62 was blocked by autophagy inhibitors as well as by the attenuation of Atg8/LC3 expression. Downregulation of p62 was required for hypoxic extracellular regulated kinase (ERK)-1/2 phosphorylation. Attenuation of p62 in normoxia activated and forced expression of p62 in hypoxia blocked the activation of ERK-1/2. The results demonstrate that hypoxic activation of autophagy induces clearance of p62 protein and implies a role for p62 in the regulation of hypoxic cancer cell survival responses.