INHBE and skin neoplasm: While Act mice never developed tumors in the absence of an oncogenic stimulus (Antsiferova et al, 2011), the double‐transgenic progeny (HPV8/Act mice) showed a strong increase in the incidence of spontaneously developing skin tumors compared to HPV8/wt animals (Fig 1F), demonstrating that activin potentiates the oncogenic action of the HPV8 transgene.