Naked mole-rats are very long-lived in comparison to near relative species, and have a great resistance to cancer - to the point at which researchers have not characterized and reported on any incidence of cancer in their laboratory colonies, now numbering thousands of individuals, and not for lack of searching. This is a far cry from similarly-sized rodent species, all of which have a very high rate of cancer. There has been considerable interest in the research community in recent years in identifying the underlying mechanisms of cancer resistance in naked mole-rats, with an eye to seeing whether or not they can form the basis for human therapies or enhancements.
Here researchers finally manage to find unambiguous incidence of cancer in naked mole-rats, which will hopefully go some way towards better understanding the mechanisms involved in the suppression of cancer in this species. Reading between the lines, I suspect that these researchers think that cancer incidence in naked mole-rats is very low but not as low as is presently implied in the literature, and there is perhaps a lack of rigor in this area of reporting. In any case, "highly resistant" is not the same thing as "immune":
In recent years, the use of naked mole-rats (NMRs) as animal models in aging and cancer research has increased as a result of their demonstrated extreme longevity and apparent resistance to cancer. We previously surveyed spontaneous histologic lesions in a zoo-housed NMR colony over a 10-year period, which revealed several age-related diseases and uncommon pre-cancerous lesions, consistent with their reported cancer resistance. However, overt cancer has not been formally documented in NMRs from either zoos or biomedical research facilities. Herein, we describe cancer in 2 NMRs and relate this to our previous findings of proliferative and pre-cancerous lesions found in additional zoo-housed NMRs with a brief discussion of diagnostic criteria of rodent neoplasia in a laboratory setting.
In Case No. 1, we observed a subcutaneous mass in the axillary region of a 22-year-old male NMR, with histologic, immunohistochemical (pancytokeratin positive, rare p63 immunolabeling, and smooth muscle actin negative), and ultrastructural characteristics of an adenocarcinoma possibly of mammary or salivary origin. In Case No. 2, we observed a densely cellular, poorly demarcated gastric mass of polygonal cells arranged in nests with positive immunolabeling for synaptophysin and chromogranin indicative of a neuroendocrine carcinoma in an approximately 20-year-old male NMR. We also include a brief discussion of other proliferative growths and pre-cancerous lesions diagnosed in a zoo colony. Although these case reports do not alter the longstanding observation of cancer resistance, they do raise questions about the scope of cancer resistance and the interpretation of biomedical studies in this model. These reports also highlight the benefit of long-term disease investigations in zoo-housed populations to better understand naturally occurring disease processes in species used as models in biomedical research.