when a person dies of cancer, what makes the heart stop beating, and the person stop breathing?

My father died of pancreatic cancer over 15 years ago. I went through his entire ordeal with him and my family and I can tell you this. It is not the cancer itself that stops the breathing. It is the cell death. and the cell death attacks the lungs first, then the hearts dies. At the end is the brain. However once the lungs stop there is no more pain. yahoo or goggle (death process) Or process of death.

I'm an MD - cancer specialist for 20 years (now retired), so I've seen the deaths of many of my patients with advanced cancers  - - been there at the bedside.  
The body just seems overwhelmed in the end - exhausted - like it has been climbing a long hill and just can't make one more step, one more breath, or one more heartbeat.  
Usually people are not awake at the end.  Oxygen delivery to the brain is decreased so that most are mercifully unconscious.  
Often the breathing becomes irregular and stops before the heart stops.  Often there is an infection - such a pneumonia -contributing.  Sometimes there is hemorrhaging (bleeding) which is usually quicker.

This is a very good and thoughtful question - - what is the last gasp, the final straw?  It's a combination of factors that leads to the body simply being worn out.  Usually poor nutrition contributes to weakness, but force feeding end stage cancer patients usually just prolongs their agony at the end.  It is usually a blessing to see this death process end.  Death appears much more restful and relaxed compared to the last struggle.  I fear the discomforts of dying more than I do death.

I gave your question a star, because I was wondering the same thing. My mom is in the final stage of pancreatic cancer, and we haven't been told exactly what happens. Thanks to the retired Dr for explaining