Monoclonal antibodies against the viral and human cellular myb gene product.

Retroviruses code for oncogenes which cause tumors in animals. The viral oncogenes have evolved from normal cellular proto-oncogenes, to which they are closely related. The viral and cellular oncogenes differ in point mutations and size, the viral genes often being truncated and, in some cases, fused to unrelated cellular genes. These differences may be responsible for the transforming function of the viral oncogenes. In human tumor cells, activated cellular oncogenes resembling the viral oncogenes have been identified. They also carry mutations and/or deletions, and in many cases are overexpressed from amplified genes. It is of interest to determine whether these activated cellular oncogenes are characteristic of certain tumors and whether their gene products can serve as tumor markers. To date, nearly two dozen viral oncogenes have been identified. Some of them are closely related to each other, and on the basis oftheir sequence homology, cellular location, and associated enzymatic activities, they can be roughly classified into three groups. The largest group is the src gene family, which consists of tyrosine-specific protein kinases that are predominantly located at the inner side of the plasma membrane. Another group consists of protein kinases which are not tyrosinebut serine-/