Who discovered the first tumor suppressor gene?

The first tumor suppressor gene, known as RB1, was discovered by researchers including Dr. Alfred Knudson in the 1970s. Knudson proposed the "two-hit hypothesis" to explain the genetic basis of retinoblastoma, a rare eye cancer in children, leading to the identification of the RB1 gene on chromosome 13. This groundbreaking work laid the foundation for understanding the role of tumor suppressor genes in cancer development.