In cancer cells, the growth is out of control. It begins with a mutation in a portion of DNA, which leads to the production of abnormal proteins. A mutation in genes involved in cell growth (proto-oncogenes), differentiation or mitosis, can result in uncontrolled growth. The proto-oncogene becomes an oncogene (1). These abnormal proteins can behave as growth stimulating factor or cell division promoting protein. So, more growth stimulating factors are produced and thus an imbalance between growth stimulating and growth inhibiting factors occurs.
On the other hand, a tumor suppressor gene (e.g. p53, p16) can be mutated (2). This results in inactivation of the gene or in formation of abnormal and thus nonfunctional protein, leading to decreased amounts of growth inhibiting factors and proteins that inhibit cell division. A mutation in a tumor suppressor gene makes oncogene activation more likely.
What is NOT true?
Extra info: Close Proto-oncogenes regulate normal cell division. When these genes are mutated, they can disregulate cell division.
Compared with benign tumours, neoplastic tumours do NOT show:
Extra info: Uniform cell mass is a feature of benign tumour
What is true about a tumor suppressor gene?
Extra info: Tumor suppressor genes appear in all cells, are not controlled by oncogenes and certainly do not code for proteins which stimulate cell division.