Answer the following question given this paragraph: 

Many cancerous cells are the products of normal cells that have lost the ability to regulate the cell cycle. The genes that encode the proteins involved in cell cycle regulation have mutations. One category of genes, called oncogenes, accelerate the cell cycle. Some cancers can be inherited, such as breast cancer (due to mutations in the BRCA1 and BRCA2 genes). Approximately five to ten percent of cancers are entirely hereditary. Other cancers are triggered by an environmental stimulus, such as through the relationship between tobacco smoke and lung cancer, or ultraviolet radiation and skin cancer.


Q: What type of cells are often the product of normal cells that have lost the ability to regulate the cell cycle?


A:
cancerous cells