TP53 and neoplasm: Differently from many tumor suppressor genes, in human cancers TP53 is actually most commonly altered by missense mutations, that not only lead to a loss/diminution of the wild type TP53 activity, but, since TP53 normally acts as a tetramer, may also function as dominant negative inhibitors over any remaining wild type TP53 activity, or even give rise to a more aggressive tumor profile through gain of function activity.