Back in the day, I worked in a lab studying the effects of an alternative NF-kB pathway on osteoclast differentiation (osteoclasts eat up bone) and growth. One of the papers demonstrated that certain anti-cancer drugs (used in breast cancer, not the ones described in this paper however) drove up regulation of that pathway, leading to increased bone resorption (thus causing osteoporosis). Now, clinically, this was probably managed fairly well with bisphosphonates, however it raises the question of whether or not these types of combo regimens are going to lead to similar types of side effects.

Regardless of that, if the results in this article are trialed, I suspect this will go exceedingly well for therapies that immunotherapies have been hard pressed to treat (alluded to in the conclusion, of course). Kudos to the group, well done.

So... this involves injecting live (but injured) cancer cells back into the body?

I think this is going to be hard to get approved.

That was the methodology for the research. The paper shows that specifc types of chemotherapy related damage can trigger desirable immunological responses, so I'd guess the end goal would be a regular chemotherapy regimen that trigger that response. The end of the abstract hints at that by saying the research provides a strategy for increased efficacy, rather than claiming to be a potential treatment or adjuvant.

Is this similar to using MRNA to create spike protein to trigger antibody response to COVID?

Same kind of idea - trick the body into creating something that will help itself, but somewhat different mechanism.

No.

Mononucleiosis actually takea advantage of DNA damage response for reproduction, which is why it leads to drastically higher rates of autoimmune disorders and immune/bone cancers