And then there is this from page 12 of this study: https://doi.org/10.1...ell.2018.02.008
"The ability of NMN to promote angiogenesis raises the question of whether it might stimulate tumor growth. Mice treated with NMN or NR for extended periods show no evidence of increased tumor burden (Mills et al., 2016; Zhang et al., 2016). Indeed, during the course of our studies, no increase in tumor burden was seen with NMN-treatment or in a DEN-induced model of hepatocarcinoma (Figures S7J and S7K), although more study is warranted."
First: LawrenceW and others: please do not post links to sites designed to evade c0py-right laws. Whatever one thinks of the ethics of such sites, you could bring a whole world of pain onto Longecity if a publisher decided to crack down on us for such. It was also not necessary in this case: as you can see from the direct link with which I've replaced the offending one, the paper is already free in full text.
Anyway: This statement is a mixture of things that aren't true and that are not actually as informative as one might think. It's just not true that the NR late-life life extension study (Zhang et al., 2016) "show[ed] no evidence of increased tumor burden:" I specifically asked the authors about pathology and cause of death, and they didn't do necropsies — they just counted dead mice.
It's true that the Imai long-term NMN study (Mills et al., 2016) showed no evidence of increased tumor burden, but this isn't very convincing: these were still young adult mice when the study ended, well before the ages at which cancer becomes evident in in reasonably well-husbanded wild-type mice. What you want to look for is an effect starting a few months out from then, during and after the 'knee' in the survival curve, and preferably to the end of life.
As far as their own substudy goes:
"DEN (diethylnitrosamine)-induced hepatocellular carcinoma model: WT mice were treated with DEN (25 mg/kg) at 14 days of age via intraperitoneal injection. Mice were weaned at 21 days of age, fed normal chow diet and treated with NMN (2 g/L) via drinking water for 20 weeks. Mice were killed and the number of surface tumors per liver was counted. Pictures of liver with tumor nodes and number of surface liver tumors (n = 10). "
That's certainly evidential, but I'm not sure how convincing it is: it's artificial, and very short-term. Also, if they're just looking at the number of surface tumors per liver, they wouldn't catch any metastases (which might be expected to increase from angiogenesis or increased SASP), You might also expect any effect on the original tumor to be most likely in a tumor type where NAMPT is commonly expressed, but this review does not mention the liver as amongst these: "colorectal, ovarian, breast, gastric, prostate, well-differentiated thyroid cancer, melanoma, glioma, and endometrial carcinoma."