Many oncolytic viruses does target other cells as well however they are not strong enough to infect or spread infection in them as the immune system mechanisms in healthy cells recognizes them and initiates defenses. However, as many cancer cells often turn off immune responses in themself as part of their cancer mechanisms they cannot defend against the virus and is killed as a result. Oncyltic viruses are often insect virus as far as i remember meaning they do not have mechanisms to avoid mammal immune mechanisms. They have showed promises and is a viable means, however as far as i know they are yet to be used in human trials.

[removed]

[removed]

[removed]

[removed]

Some of them as injected inside or nearby the tumor, that by itself makes things easier. Other thing is that some of these viruses are genetically modified in such a way that they need a certain apparatus to multiply that only tumor cells have, such as a higher metabolism and a higher multiplication rate - and therefore different amount of organeles and different signaling pathways

I work and research oncolytic adenoviruses that are used for cancer treatment; the virus our lab uses makes use of two selection characteristics. The first is a modification to the casid "fiber" which only allows infection of cells over expressing integrins, which are associated with many types of tumors. The other mechanism to restrict replication to cancer cells relies on modifications to the virus genome; which in turn only allow for replication in a cell where the retinoblastoma gene is dysfunctional. The adenovirus protein normally binds to retinoblastoma to stop surveillance mechanisms that would push the cell through mitotic stages. If you remove the gene expressing this protein, the adenovirus can only replicate in retinoblastoma deficient cells. Retinoblastoma also is deficient in most cancer cells, but not in normal cells.

Don't cancer cells have their own defence mechanisms? Highly respect your work by the way!

They definitely do, which is why oncolytic virotherapy is not as simple as just direct oncolysis of tumor cells. It also relies on the highly immunogenic virus to attract T cells and other lymphocytes that may recognize the tumor to the microenvironment (antigen spreading).

It is also why these two modifications to our virus were chosen, integrins and retinoblastoma dysfunction are vital for a successful cancer cell.