Off topic:How do I validate my findings?

Question

[Na Sed]

I am working on effective miRNA-mRNAs interactions in cancer A. So I just do statistical tests for tumor samples.

Now, I have been asked to validate my findings, claimed effective miRNA-mRNA interactions, using Normal samples. However, I do not have normal samples!

I remember that I saw somewhere or heard from someone that in such case which I do not have normal samples, I can consider an unrelated cancer and do the same tests on this cancer. Then, I can compare the results of both of them and count how many interactions are common between two cancers. If there is no common interactions, or just a few common interactions, I can say my findings are significant and reliable.

Now I have three questions:

1. What do you think about the bolded paragraph? Is it correct?
2. Is it rational if I run my tests on a related cancer and expect to have many common miRNA-mRNA interactions? If so, how many interactions must be common to say that my results are reliable and significant?
3. Is it rational if I run my tests on normal samples from a different tissue? In this case, must I do expect to have no common interactions between the cancer and these normal samples?

PS. If you know some references in this context, I appreciated if you introduce to me.