Action, reaction or cause and effect is the base of everything, both in physical as well as metaphysical form. To explain effect of emotions on chemicals and electric impulse in brain, I consider any living being comprising of three main parts. One physical body having physical mind (brain), two metaphysical body (identical to physical one, name it soul) and three the real unconceivable self (life force, name it the God).
Part three is just inactive but provides the kick start of the various functions existing in both metaphysical and physical systems (bodies). As regards the effect, physical matter affects the physical & metaphysical body of the living being and reversably metaphysical mind affects the physical mind (brain) resulting in different types of chemical and electric impulses. To the extent cause and effect basis I would say based on Karmic balance carry over on to the next birth's genes, DNA, RNA is fixed before hand.
Thus, I am sure the emotions can develope as well as cure various types of diseases including cancer. The power of mind (thought) is limitless. Only ones should have technique of taming it to suit one's requirements.
