In contrast, the absence of HSP70 in the homozygous KO animals almost completely blocked mammary tumor development: within >100 weeks no tumors appeared in 10 out of 11 animals, and in one HSP70−/−neu+/− mouse a tumor appeared by 88 weeks of age, which is far later than tumor appearance in control animals. The gene discussed is HSPA1A; the disease is neoplasm.