Covers growth factors as cell messengers that signal through receptors and drive the G1-S transition, including their routes of diffusion and role in stem cell reprogramming. It then describes tumour suppressors Rb and p53, proto-oncogenes and oncogenes with c-Myc, HER2 and FGFR, and the main oncogenic RNA and DNA viruses such as HTLV-1, HPV, EBV and HBV. Mnemonics for each section are included.
Topic 29 of 105 in the MU Sofia syllabus for Biology (Medicine, Year 1). The free AceMed note covers it in 6 sections, about 1,044 words (8 min of reading), with 11 flashcards.
Growth Factors – The Cell’s Green Light for Growth
Tumor Suppressor Genes – The Cell’s Brakes
Proto-oncogenes and Oncogenes – When Good Genes Go Bad
Oncogenic Viruses – When Infection Leads to Cancer
MNEMONICS
Growth Factors – The Cell’s Green Light for Growth
Growth factors are proteins that serve as messengers between cells, helping to regulate key processes such as growth, healing, and cell differentiation. Here's how they work:
Bind to specific receptors on the surface of target cells to trigger intracellular signaling cascades.
Their effects vary depending on the type—e.g., EGF, FGFs, and VEGFs stimulate skin, connective tissue, blood vessel, and nerve cell regeneration.
Once bound, they activate intracellular enzymes that transmit signals to the nucleus.
These signals lead to the production of proteins that promote the G1-S transition in the cell cycle (the point where a cell commits to division).
Signaling routes include:
Endocrine, paracrine, autocrine, and intracrine diffusion.
Direct contact with receptor proteins embedded in membranes or extracellular matrix.
They are vital in stem cell regulation, helping:
Induce differentiation into specific tissues (e.g., retinal cells for transplantation).
Reprogram adult cells into induced pluripotent stem cells (iPSCs) using Yamanaka factors (Oct3/4, Sox2, Klf4, and c-Myc).
These factors act as the “GO” signals for the cell cycle, working alongside cyclin-CDK complexes to ensure timely progression through cell division.
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