View source for 42. Oncogenes, protooncogenes, oncoproteins. Growth factor and growth factor receptor oncogenes (RET, KIT, PDGFR). Overexpression of normal growth factor receptors (ERBB1, ERBB2). Organ examples.

''I recommend starting with the relevant medical biochemistry topic (27 - 28) before getting into this''.

All cancers start with some genetic damage. This genetic damage is always ''nonlethal'', meaning that the damage isn’t big enough to actually kill the cell, however it is definitely big enough to cause some serious damage. The process where cancer develops is called ''carcinogenesis''.

Nonlethal genetic damage causes mutations and can be due to many factors. Common factors include environmental agents like chemicals, radiation and viruses.

Take a step back and think about this: All tumors begin as a single progenitor cell that acquires some genetic damage, which then undergoes ''clonal expansion'', where this cell divides into two, and these two divide into four, and so on. All tumors originate from one single cell, meaning that every tumor is ''monoclonal''.

Five types of genes are normally mutated in cancers:

* Proto-oncogenes
* Tumor suppressors
* Genes that regulate apoptosis
* Genes involved in DNA repair
* Micro RNAs

Let’s talk about each of them in detail.