Cause of or cause for

Hi everyone.
1.It's a main cause of cancer.
2.lt's a main cause for cancer.
I guess (1) is correct but why? What's the difference between ' cause of' and 'cause for'?
* Can we replace 'cause' by ' reason'?
4.It's a main reason of cancer.
5.It's a main reason for cancer.
*Aside from the sentences above, does the word 'reason' take the preposition 'for' or 'of' after it?
Thanks in advance