Question

fill in the blank:

Tumor cells secrete VEGF as a ___________ signal which binds to the VEGFR on the surface of vascular endothelial cells, stimulating mitosis of these cells and producing blood vessels to supply the tumor with oxygen and nutrients.

a) autocrine

b) paracrine

c) endocrine

Answer 1

Autocrine signaling is via signaling factors that are produced by one cell that act on the same cell. When the signals produced by one cell act on neighboring cells , it is paracrine signaling. If the signals are produced by endocrine glands and act on the target tissue, it is called endocrine signaling.

When vascular endothelial growth factor is secreted by tumor cells and bind to VEGF receptors on endothelial cells, it is paracrine signaling. Tumor cells lie near the endothelial cells ijn blood vessels within the tumor. As a result, the endotehlial cell divide by mitosis and lead to formation of blood vessels. If tumor cell produced VEGF acts on tumor cells itself, it is autocrine signaling. If endocrine glands secrete VEGF and it acts on target tissues, it is endocrine signaling.

Right choice: b) paracrine.