ERBB4 and neoplasm: In results that are similar to those shown elsewhere in this report, mutations that disrupt ErbB4 kinase activity (K751M), ErbB4 cleavage by gamma-secretase (V673I), ErbB4 interactions with steroid hormone receptors (LL783/4AA), ErbB4 interactions with Bcl family proteins (L985A), and ErbB4 phosphorylation at Tyr1056 (Y1056F) all disrupt inhibition of clonogenic proliferation of (or disrupt tumor suppressor activity in) the PC-3 (Figure 6) and DU-145 (Figure 7) human prostate tumor cell lines (Table 4).