Thus, ErbB4 kinase activity, ErbB4 cleavage by gamma-secretase, ErbB4 interactions with steroid hormone receptors, ErbB4 interactions with Bcl family proteins, and interactions with effectors via binding to ErbB4 phospho-Tyr1056 all appear to be critical for the tumor suppressor activity of the constitutively-active ErbB4 Q646C EGFP-TVV construct. The gene discussed is ERBB4; the disease is neoplasm.