Low Incidence along with Low mRNA Levels of in Prostate and Colorectal Cancers Compared to Glioblastoma.

The presence as well as the potential role of EGFR in tumors other than glioblastoma still remains a controversial subject with many contradictory data published. Previous analyses, however, did not consider the level of mRNA expression in different tumor types. Appropriately designed protocol for Real-time quantitative reverse-transcription PCR (Real-time qRT-PCR) was applied to analyze and mRNA expression in 155 tumor specimens. Additionally, Western Blot (WB) analysis was performed for selected samples. Stable cell lines showing EGFR expression (CAS-1 and DK-MG) were analyzed by means of WB, immunocytochemistry (ICC) and fluorescence hybridization (FISH). Our analyses revealed expression in 27.59% of glioblastomas (8/29), 8.11% of colorectal cancers (3/37), 6.52% of prostate cancers (3/46) and none of breast cancers (0/43). Despite the average relative expression of varying greatly among tumors of different tissues (approximately 800-fold) or even within the same tissue group (up to 8000-fold for GB), even the marginal expression of mRNA can be detrimental to cancer progression, as determined by the analysis of stable cell lines endogenously expressing the oncogene. EGFR plays an unquestionable role in glioblastomas with high expression of this oncogene. Our data suggests that EGFR importance should not be underestimated even in tumors with relatively low expression of this oncogene.