Markers of drug resistance in relapsing colon cancer.

PURPOSE: 5-Fluorouracil failure and drug resistance, which often occurs during chemotherapy, is still a great obstacle to the success of human colon cancer treatment. Thus, the comparative study of markers of drug resistance in cancer cells before and after chemotherapy may be extremely helpful in the selection of the appropriate chemotherapeutic drug in colon cancer patients who fail adjuvant treatment with 5-fluorouracil. In the present study we examined the differential expression of three multidrug resistance-related proteins (i.e., P-glycoprotein, MRP, and LRP) and of topoisomerase IIalpha in a series of 20 primary colon carcinomas and their recurrences. METHODS: All markers were determined at tissue level by three-step immunohistochemistry using appropriate monoclonal antibodies, and the markers' immunopositivity was quantified by image analysis. In addition, Feulgen stain was used for the assessment of nuclear DNA content of malignant cells at their primary location. RESULTS: Some degree of aneuploidy was detected in all primary carcinomas. The immunoexpression of the three multidrug resistance-related proteins did not change significantly, either qualitatively (positivity vs negativity) or quantitatively, after chemotherapy. On the contrary, the percentages of topoisomerase IIalpha-positive malignant cells were significantly increased in the tumour recurrences by comparison to their primary locations ( P=0.011). CONCLUSIONS: According to our results, increased topoisomerase IIalpha immunohistochemical expression appears to be part of the malignant cells' phenotype in recurrent colon cancers. Therapeutic options after failure of 5-fluorouracil-based treatment could therefore include appropriate topoisomerase IIalpha-targeted drugs.

Immunodetection and clinico-pathological correlates of two tumour growth regulators in laryngeal carcinoma.

Activation of telomerase, present in the vast majority of all human cancers, is associated with elongation of chromosomal telomeres and consequent cell immortalization. Telomere length homeostasis is a dynamic process governed by the negative feedback mechanism of the telomeric repeat binding factor 1 (TRF1) which inhibits the action of telomerase in telomerase-positive cells. In an attempt to investigate markers of tumour growth as possible prognostic indicators in laryngeal cancer, we studied the expression of TRF1 and of the proliferation marker Ki67 on 96 invasive squamous carcinomas of the larynx. A standard three step immunoperoxidase staining method was applied on paraffin sections incubated with appropriate polyclonal antibodies. The percentages of Ki67- and TRF1-immunopositive cancerous cells were calculated by image analysis. Univariate and multivariate statistical analysis of the staining results were performed in order to detect any association of the examined immunomarkers with the tumours' classical clinicopathological variables including nuclear morphometric features as well as with patients' disease-free survival. Ki67 immunostaining was positively linked with advanced patients' age, nodal involvement as well as presence of early recurrence. No relation was found between proliferative fraction and TRF1 immunoexpression. TRF1 was expressed in 55.2% of all cases and was positively linked only to tumour size. Multivariate statistical analysis revealed the presence of lymph nodal metastasis and Ki67 immunopositivity index > or = 20% as significant predictors of relapse. Increased Ki67 immunostaining appears to be a promising marker of tumour aggressiveness in laryngeal cancer. After one point at the tumour's natural history, the maintenance of tumour growth does not seem to depend on cell proliferation but on TRF1 immunoexpression. Whether the latter can be used for the identification of immortalized cells in every-day practice is worth investigating.