What stimulates the pollen tube to grow

Synergids stimulates the pollen tube to grow.

In homeostasis fashion, cells undergo balanced cell division and programmed cell death (apoptosis) through regulated signalling.This maintains tissue integrity. On the one hand, Proto-oncogenes promotes cells proliferation. On the other hand, tumors suppressors inhibit cell growth and division especially in cells with damaged dna.
Therefore mutations on these oncogenes could result to uncontrolled cell proliferation. Cancer cells also overexpress angiogens that results to proliferation of blood vessels in tumors. This contributes to their metastasis in the body.