How could a saved person, that has eternal life abiding in them, kill themselves? It is impossible.
Not everyone that saith unto him Lord Lord will enter the kingdom of heaven. Do you think that suicide is, as Jesus said, "doing the will of your Father which is in heaven"? I think not.
Also, depression and cancer are curses which came from the law. This part is where God talks about what happens if you don't hearken to his voice to do what he commands:
depression and madness: Deu 28:28 The LORD shall smite thee with madness, and blindness, and astonishment of heart:
cancer: Deu 28:27 The LORD will smite thee with the botch of Egypt, and with the emerods, and with the scab, and with the itch, whereof thou canst not be healed.
bad luck, cowardice: Deu 28:25 The LORD shall cause thee to be smitten before thine enemies: thou shalt go out one way against them, and flee seven ways before them: and shalt be removed into all the kingdoms of the earth.
Plus, we also know that Saul from the old testament, an evil man, as well as Judas Iscariot, killed themselves, which gives further credence to the theory that suicides go to hell.
1Sa 31:4 Then said Saul unto his armorbearer, Draw thy sword, and thrust me through therewith; lest these uncircumcised come and thrust me through, and abuse me. But his armorbearer would not; for he was sore afraid. Therefore Saul took a sword, and fell upon it.
We (the church) have had the cure to cancer for 2 thousand years now. His name is Jesus.