Associations between neoplasia incidence and telomere biology
We compiled neoplasia incidence rates in 7 species of mammals from a
medically curated postmortem database published by Boddy et al. (2020)
in addition to 15 species from various sources in the literature
reviewed by Albuquerque et al. (2018) and shown in Table S10. In all
studies, the number of individuals with abnormal growth including both
benign and malignant tumors (neoplasia) out of the total number of
necropsies were used to define the neoplasia prevalence rate (%). For
the large treeshrew (Tupaia tana ) neoplasia rate is unknown, so
we used the estimate reported for the closely related common treeshrew
(Tupaia glis ). Due to small samples sizes, neoplasia data were
combined in Boddy et al. (2020) for the Asian and African elephant
(Elephas maximus and Loxodonta africana ), so we used the
average TL, mass and lifespan of the two species, which are similar
(Table S9), in subsequent analyses. Boddy et al. (2020) also provided
estimates of lifetime prevalence of malignant neoplasms (invading
surrounding normal tissue) of 29 mammal species, allowing us to test if
neoplasia prevalence is generally a good predictor of malignancy
prevalence (i.e. cancer rate in %). Most neoplasia data are from wild
animals kept in captivity with no age or sex information, and not all
tissues were investigated during necropsies, thus the data only provide
crude estimates of the natural rate of spontaneous cancers.
Species mean telomere length measured using the TRF method allows
comparisons of absolute TLs and were collected from both Gomes et al.
(2011) and Seluanov et al. (2007) to increase sample size (Table S10).
Six overlapping species in these two studies show that the TL
measurements are highly correlated (R²=0.9431), but consistently higher
in Seluanov et al. (2007). We therefore used an ordinary linear
regression of TLs of the overlapping species to adjust measurements of
the four species (Table S10) from Seluanov et al. (2007) to match Gomes
et al. (2011) using the formula: 0.6617 x TL - 2.4454 kb. Telomerase
activity was measured using different methodologies, so we can only
report whether telomerase was present (1) or absent (0) in the somatic
cells of the species. We then test phylogenetic bivariate associations
between neoplasia rate and TL, telomerase expression, adult body mass
and maximum lifespan (obtained from the AnAge database, Tacutu et al.,
2018), and whether TL and/or telomerase expression predict neoplasia
rates (response variable) using phylogenetic multiple regression as
described above.