UroToday- ErbB3 is a growth factor receptor involved in cell proliferation, differentiation, angiogenesis, survival and apoptosis. The activation of ErbB3 requires ligand binding and phosphorylation by other tyrosine kinases. A study examining cellular distribution of ErbB3 in prostate cancer (CaP) specimens was performed by Dr. Koumakpayi and associates from Montreal, Canada and appears in the online version of the BJU International. They found that patients negative for nuclear ErbB3 staining had an increase in biochemical recurrence (BCR) after radical prostatectomy (RP).

A cohort of 55 men with positive surgical margins (PSM) following RP was included in the study, none had adjuvant treatment. Clinical and pathologic variables were included in the multivariable analysis. Immunohistochemical staining for ErbB3 was performed with a polyclonal antibody and quantified by 2 observers who scored 10 randomly selected tumor regions of each specimen. The staining intensity was scored as 0 for absence, 1 for weak, 2 for moderate and 3 for strong ErbB3 staining of the membranes and cytoplasm. The percentage of CaP cells with moderate to strong nuclear ErbB3 staining was also quantified. Nuclear ErbB3 staining >25% was scored as positive.

The median time to BCR was 33 months and 78% of men had experienced a BCR at the time of the study. ErbB3 staining in normal prostate glands next to cancerous regions was mostly cytoplasmic, whereas CaP areas had both cytoplasmic and nuclear staining. The results demonstrate that 28 of the 55 patients (51%) had moderate to strong cytoplasmic staining, whereas 20 (36%) were positive for nuclear ErbB3. There was a correlation between nuclear ErbB3 expression and BCR within 3 years but there was no correlation between cytoplasmic ErbB3 expression and any clinicopathological variables. The cytoplasmic expression of ErbB3 had no correlation with BCR at 3 year. The probability of remaining BCR-free at 3 years was 0.65 for men with nuclear ErbB3 and 0.34 for nuclear ErbB3-negative men. Multivariable regression showed that only nuclear ErbB3 and lymph node invasion retained their prognostic value as independent markers.

Koumakpayi IH, Diallo JS, Le Page C, Lessard L, Filali-Mouhim A, B├ęgin LR, Mes-Masson AM and Saad F

BJU Int. ePub: May 26, 2007
doi: 10.1111/j.1464-410X.2007.06992.x

Reported by UroToday Contributing Editor Christopher P. Evans, M.D

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