Can you explain gene regulating proteins to me like I’m in the 5th grade?

A friend of mine was recently diagnosed with Glioblastoma. It’s a very aggressive brain cancer.

A different friend of mine just sent me an article about some research being done. The article states that The reactivation of a dormant retrovirus, HML-2, may contribute to the aggressiveness of glioblastoma, a type of brain tumor.

Researchers discovered that the virus influences the stemcell state of the tumors, thereby promoting a more resistant form of cancer. HML-2 was found to affect stem cell programming via a gene-regulating protein named OCT4.

If the above is true, does that mean the virus is contagious and only people with the right genes would have a problem? Or, the right protein to activate the gene? Where does the protein come from?

Is the gene in the person from birth, or it’s a gene in the cancer?