Pitfalls in the assessment of MGMT expression and in its correlation with survival in diffuse astrocytomas: proposal of a feasible immunohistochemical approach.

Immunohistochemical studies showed that O(6)-methylguanine-DNA methyltransferase (MGMT) protein expression is negatively associated with survival in glioblastomas treated with alkylating agents in accordance with previous results of methylation-specific PCR. Implementation of this data in routine clinical diagnostics is limited due to often inappropriate study designs, e.g. pooling of tumor entities, WHO grades or primary and secondary glioblastomas, disregard concerning the infiltration zone or various epidemiological factors. The aim of our study was to evaluate MGMT expression and its prognostic value taking into consideration the aforementioned deficiencies. For this, 162 astrocytic tumors WHO II-IV (36 diffuse astrocytomas WHO II, 51 anaplastic astrocytomas, 75 primary glioblastomas) as well as 25 glioblastoma infiltration zones and 19 glioblastoma relapses were analyzed for immunohistochemical MGMT protein expression using tissue microarray technique. Expression of MGMT significantly decreased from WHO grade II (25.6%) to glioblastoma (16.8%, p = 0.01) with lowest levels in grade III tumors (10.2%, II/III p < 0.0001). Significant negative associations of MGMT and survival were detected for WHO grade II and IV (p = 0.003 and 0.013). The optimal cut-off value of MGMT positive nuclei in primary glioblastomas discriminating patients with significantly different survival rates was at 15% (Log-Rank p = 0.0002). Individual relapse tumors showed changes of MGMT expression to a varying degree. The infiltration zone demonstrated a significant increase of MGMT (p < 0.0001). We conclude that immunohistochemical MGMT assessment has potential as a powerful diagnostic tool but analysis should only be performed in a grade dependent manner, before radio-/chemotherapy and with special attention to the infiltration zone of diffuse astrocytomas.

A multivariate analysis of adhesion molecules expression in assessment of colorectal cancer.

BACKGROUND AND OBJECTIVES: Adhesion molecules are implicated in the progression of colorectal cancer (CRC). Despite the evidence of association between their expression and patients' prognosis, the data have not been examined simultaneously in a same study; thus, the relative clinical value remained largely unknown. The aim of this study was to identify the adhesion factors that display the most significant prognostic value for CRC patients to guide clinical decision-making regarding appropriate treatment. PATIENTS AND METHODS: We examined by immunohistochemistry, the expression of E-cadherin and its associated catenins, alpha(alpha)-catenin and beta(beta)-catenin, DCC, and CD44 and its partner, MT1-MMP in a series of 140 CRC tissues at intermediate Stage II and Stage III to determine their prognostic significance. RESULTS: Clinicopathological survey indicated an inverse relationship between E-cadherin expression and tumor differentiation, and an association between CD44 expression and venous invasion. Univariate and multivariate analyses showed that loss of expression of E-cadherin and CD44 significantly correlated to poor survival, especially in Stage II. Combination studies indicated that loss of E-cadherin and loss of CD44 had the worst impact on patient prognosis, particularly in colon cancer. CONCLUSION: Immunohistochemical staining of E-cadherin and CD44 may help to identify a subgroup of high-risk patients with Stage II CRC, especially in colon cancer, who may need intensive follow-up and appropriate therapeutic strategy.