While I can't speak to whether there are enzymes for the proper copy/paste I do have a set of random cancer related bits I've picked up over the years.

There are some basic, well-known nutritional interventions that are generally important/critical for DNA repair processes. The 2 main ones are Vitamin D and Magnesium. Ensuring adequate amount of these tend to be helpful (most folks aren't getting enough sun and greens).

Other than that, a steady and adequate source of the substrates seems to be important: ie protein (nitrogen), and phosphates.

One of the interesting bits about some cancer cells is that while they simply haven't gone through apoptosis, physical sheer stress incurred from physical activity (exercise) can cause cancer cells that travel beyond the tumor point (before it becomes metastatic) to finally self destruct.

It seems important to me that the best strategy for cancer is the compounding of many different strategies that optimize the body's innate defenses to run optimally.

It does seem that ketogenic diets may have adjuvant properties, but there is yet to be a clinical trial that demonstrates it, so it's basically stuck in paper and R&D stages as to whether being in a ketogenic state can be one of the last areas that may help cancer patients extend lifetime from say 1 year to 2 years.