BIOL3108 Lecture Notes - Lecture 22: Basal-Cell Carcinoma, Micrometastasis, Tumor Microenvironment
Document Summary
About the formation of secondary tumours, at a distance from the initial, primary tumour. 90% of cancer deaths are caused by metastasis. Secondary growths in brain, liver, bones and lungs. Some tumours frequently metastatic (e. g. : pancreatic, breast, colon) Some tumours never metastasise (e. g. : basal cell carcinoma) Some primary tumours home to specific sites (tropism) No evidence for new genetic mutation in the metastasis process -> but there is a very strong selection for the classical driven mutations present in the primary tumour. The secondary tumour is usually quite homogenous compared to the primary tumour or typical tissue, which typically has very varied/heterogeneous mutations. Requires degradation of basement membrane ecm -> comprised of collagen iv, laminin. Degradation occurs via matrix metalloproteases (mmps) of which are secreted by the tumour cells. Tumours that have an intact basement ecm do not undergo local invasion -> don"t develop distant metastasis. Occurs commonly in squamous cell carcinomas -> known to commonly metastasise.
