This English doctor is apparently one of those terminally online twitter-heads who tweets constantly, so it was hard to find any context for this one tweet. However the original tweet appears to be referring to oncoviruses in general, not any specific "cancer virus".

I think this is the same SV40 the Japanese man is talking about. Wikipedia does say: "Due to its high tissue tropism, biotechnology companies seek to utilize modified SV40 based vectors as a viral vector for gene therapy." ... So maybe this isn't that surprising? Assuming it's the same SV40 we're talking about, there's also an article specifically about its possible link to cancer.

What I found more interesting was his last question: "The plasmid DNA map submitted by Pfizer to the EMA (European Medicines Agency) does not appear to include SV40. Why did they hide it?"

This English doctor is apparently one of those terminally online twitter-heads who tweets constantly, so it was hard to find any context for this one tweet. However the original tweet appears to be referring to oncoviruses in general, not any specific "cancer virus".

I think this is the same SV40 the Japanese man is talking about. Wikipedia does say: "Due to its high tissue tropism, biotechnology companies seek to utilize modified SV40 based vectors as a viral vector for gene therapy." ... So maybe this isn't that surprising?

What I found more interesting was his last question: "The plasmid DNA map submitted by Pfizer to the EMA (European Medicines Agency) does not appear to include SV40. Why did they hide it?"