metallothionein and Rectal-Neoplasms

The study aimed at the evaluation of the effects of radiotherapy on expression of metallothionein (MT) isoforms, both in the form of quantitative alterations in mRNA, and differences in expression of MTI/II proteins in rectal tumours.. Material for the study originated from 21 patients with rectal cancer at stage II or III. Material for immunohistochemical studies [MTI/II, Minichromosome Maintenance Protein 3 (MCM3), Ki-67] and real-time polymerase chain reaction (PCR) (mRNA of MT1F, MT1X and MT2A) was sampled twice: during rectoscopic examination before the start of the preoperative radiotherapy (samples A) and from the post operative specimen, following radiotherapy (samples B).. The level of mRNA expression for each of the studied MT isoforms was higher in cancer cells subjected to irradiation. The most extensive differences were observed for the MT2A isoforms (p=0.09). No differences were disclosed between samples A and B in expression of MT I/II protein. The material sampled after radiotherapy manifested a tendency for reduced proliferative activity of the tumour cells: the decrease of MCM3 expression was significant (p=0.022), while in the case of Ki-67, the difference approached statistical significance (p=0.096).. Application of radiotherapy to rectal adenocarcinoma cells is followed by an increase in MT mRNA expression level, affecting first of all the MT2A isoform. However, we failed to note an increased expression of MTI/II protein coded by the gene. Moreover, application of radiotherapy was followed by a decrease in expression of MCM3 protein. Our results cannot clearly confirm induction of MT after irradiation of human adenocarcinoma cells. The role of MT in radioprotection remains ambiguous.

Topics: Adenocarcinoma; Aged; Aged, 80 and over; Cell Cycle Proteins; DNA-Binding Proteins; Female; Gene Expression; Gene Expression Profiling; Humans; Immunohistochemistry; Ki-67 Antigen; Male; Metallothionein; Middle Aged; Minichromosome Maintenance Complex Component 3; Nuclear Proteins; Protein Isoforms; Real-Time Polymerase Chain Reaction; Rectal Neoplasms; RNA, Messenger

Metallothioneins (MT) are low-molecular weight, metal-binding proteins that play a role in cellular proliferation and differentiation, as well as in cellular defense mechanisms. They act as scavengers of free radicals produced by irradiation. A number of in vitro and in vivo studies have linked overexpression of cellular MT with tumor cell resistance to radiation. This is the first study that investigates whether MT expression is involved in the radioresistance of rectal carcinoma.. Using a mouse monoclonal antibody, MT expression was analyzed by immunohistochemistry on surgical samples (n = 85) from 85 patients with locally advanced rectal carcinoma who were treated preoperatively with a hyperfractionated and accelerated radiotherapy schedule and on tumor biopsies (n = 13) obtained before treatment. The potential correlations between MT expression and pathologic variables and survival were examined.. MT were expressed strongly in both the cytoplasm and nucleus of tumor cells in 7 biopsy and 42 surgical samples. A comparison of MT expression in biopsy and surgical specimens showed that MT expression did not change after irradiation in most cases. Against all expectations, MT were expressed more frequently in tumors from responders than in those from the nonresponders (P = 0.02). There was no correlation between MT expression and tumor stage, histology after radiotherapy, or survival.. These findings do not Cansupport the hypothesis that MT overexpression at the end of radiotherapy is a marker for radiation resistance.

Topics: Adult; Aged; Aged, 80 and over; Animals; Antibodies, Monoclonal; Biomarkers, Tumor; Dose Fractionation, Radiation; Female; Humans; Immunohistochemistry; Male; Metallothionein; Mice; Middle Aged; Neoplasm Recurrence, Local; Rectal Neoplasms

Rectal carcinomas of previously untreated patients were analyzed for oxygen status using a computerized polarographic needle electrode histograph. Microvessel density and expression of c-jun, vascular endothelial growth factor (VEGF) and several resistance-related proteins (glutathione S-transferase-pi, GST; thymidylate synthase, TS; metallothioneine, MT) were determined using immunohistochemistry. To examine whether a relationship exists between intratumoral vessel density and tumor oxygenation, microvessel counts were determined in a 400x field using factor-VIII-related antigen and were correlated with the corresponding pO2 values. Linear regression analysis revealed a significant relationship between vessel density and oxygenation status of the tumors. Expression of c-jun, VEGF and resistance-related proteins was correlated with microvessel counts and pO2 values. Significantly lower vessel counts were found in GST- and MT-positive tumors and in tumors with overexpression of c-jun and VEGF than in negative tumors. In addition, significantly lower pO2 values were found in c-jun- and VEGF-positive tumors as well as a tendency for pO2 values to be lower in tumors where MT, GST and TS were expressed. These data show that expression of c-jun, VEGF, and resistance-related proteins is linked with poor vascularization and low oxygenation status in rectal cancer.

Topics: Glutathione Transferase; Humans; Metallothionein; Neovascularization, Pathologic; Oxygen; Rectal Neoplasms; Thymidylate Synthase