Research demonstrates a bat species' resistance to cancer, pinpoints key genes

By Hugo Francisco de SouzaReviewed by Susha Cheriyedath, M.Sc.Feb 18 2024

In a recent study published in the journal Nature Communications, researchers investigated seven species of bats to verify hypotheses about their potent cancer resistance empirically. A combination of in vitro and in vivo techniques revealed that one species, Myotis pilosus, displayed particular cancer resistance despite researchers intentionally activating the ontogenetic genes in their primary cells. Analysis of this phenomenon using transcriptomic and functional tests suggested that the unexpectedly potent downregulation of HIF1A, RPS3, and COPS5 genes and the loss of a COPS5-promoting enhancer along the HIF1A sequence may be the key behind M. pilosus' extreme cancer resistance.

Study: Experimental evidence for cancer resistance in a bat species. Image Credit: Rudmer Zwerver / Shutterstock

Bats are proof that not all animals are built equal

Bats are considered one of the best-adapted mammalian groups in terrestrial and particularly arboreal environments. Bats come in all spaces and sizes, from the penny-sized Kitti's hog-nosed bat to the six-foot-wide-wingspan flying fox and all 1,400 species in between. When accounting for the fact that bats comprise approximately 20% of all known mammalian species, their success becomes evident.

Scientists have studied bats to pinpoint the secrets of their success. Thus far, they believe the evolutionary dominance of bats to be attributable to a few crucial adaptations, most notably their evolution of actual flight, echolocation, high viral resistance, and commendable longevity. Their longevity, in particular, is extraordinary and comparable to genuine relative size-age outliers like the naked mole rat and blind mole rat. Indeed, 18 out of 19 size-corrected mammalian species with natural lifespans longer than our medically-assisted ones are bats, with some species like Myotis myotis living eight times longer (41 years) than expected by size alone.

Given the observed evolutionary interplay between cancer and longevity, bats are hypothesized to mirror naked mole rats and elephants in having evolved adaptations that prevent cancer onset and proliferation. Unfortunately, this hypothesis remains untested within an empirical scientific framework. Verifying this hypothesis and elucidating the mechanisms responsible would provide crucial insights into natural cancer resistance and the potential for developing novel anticancer therapeutics.

About the study

In the present study, researchers used somatic tissues (e.g., skin grafts) and genetic material from seven bat species to investigate their cancer resistance in vitro and in vivo. The included species were Chinese and comprised the big-footed bat (Myotis pilosus; MPI), the least horseshoe bat (Rhinolophus pusillus; RPU), the Szechwan myotis (Myotis altarium; MAL), the greater horseshoe bat (Rhinolophus ferrumequinum; RFE), the great leaf-nosed bat (Hipposideros armiger; HAR), the Chinese rufous horseshoe bat (Rhinolophus sinicus; RSI), and the Leschenault's Rousette (Rousettus leschenaultii; RLE).

Researchers additionally used tissues from Mus musculus, the typical rat lab, as controls for all experiments. To gain insights into the resistance of sampled tissue to malignant transformation, systematic investigations of the tumor resistance of primary fibroblasts were carried out by priming fibroblasts to express oncogenic HRAS(G12V) and SV40 large antigen (SV40 LT) genes, followed by protein level quantification using immunoprecipitation assays. These Vitro assays were supplemented from luciferase immunofluorescence assays carried out in genetically modified murine (MSF^HRAS\SV40LT) and MPI (MPI-SF^HRAS\SV40LT) fibroblasts.

Once the atypical cancer resistance of MPI fibroblasts was established, researchers investigated the mechanism underlying observed resistance using transcriptome sequencing of fibroblasts, thereby identifying differential expression patterns of fibroblast-associated genes. Analyses included the signed weighted gene co-expression network analysis (WGCNA), the in-tandem computing of the module eigengene (ME), and the de-novo development of a protein-protein interaction network derived from the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database.

To test if observed cancer resistance could be a function of specific gene downregulation, CRISPR-Cas9 gene-editing technologies were used to inhibit the expression of genes known to affect cancer resistance, including HIF1A, COPS5, RPS3, EP300, and EIF5B in MSF^HRAS\SV40LT. Finally, to elucidate the molecular basis underpinning natural gene downregulations, conserved non-coding elements (CNEs) were analyzed via the creation of a de-novo MPI genome followed by the Assay for Transposase-Accessible Chromatin using Sequencing (ATAC-seq assay).

Study findings – not all bats are built equally, either

Both in vitro and in vivo fibroblast assays revealed that MPI fibroblasts were significantly more resistant to cancer and cancer-associated proliferation than controls and the other six investigated bat species. MPI fibroblast colonies were consistently found to be substantially smaller than those of the other tested cohorts, validating its profound anticancer properties. Repeating these experiments using other tissue types (intestine and tail tissues) provided comparable results, validating these findings and the hypothesis of bats displaying natural cancer resistance.

Transcriptomic protein expression quantification assays present that the relative expression levels of MPI HIF1A, EP300, EIF5B, COPS5, and RPS3 genes were significantly lower (downregulated) compared to the other cohorts, suggesting oncogene downregulation as the mechanism of action underpinning observed fibroblast results.

"Our results showed that the suppression of HIF1A, COPS5, and RPS3 expression significantly inhibited cell proliferation (P < 0.05; two-tailed Student's t tests. However, the downregulation of EP300 and EIF5B had no remarkable effect on cell proliferation. Notably, these two genes were up-regulated during aging in the long-lived bat (Myotis myotis), suggesting their potentially pleiotropic roles in the bat lifespan."

CNE analysis revealed a total of 437,414 CNEs across all evaluated species, 20,231 of which displayed accelerated evolution in MPI. ATAC-seq assays refined these results and highlighted that mutations in CNE143336, a potential regulatory element, could result in substantial transformation resistance via HEK 293T and NIH 3T3 gene modulation. Finally, cell-derived xenograft models revealed the essential role of COPS5 genes in malignant transformation resistance.

Conclusion

The present study empirically verifies preexisting hypotheses regarding bats' natural anticancer resistance. It elucidates the mechanisms underpinning MPI's remarkable anti-malignant-transformation potential using a combination of immunological, transcriptomic, and gene-editing techniques. Study findings highlight the role of gene downregulation and epigenetics as the basis for the natural cancer resistance of some bat species.

It is essential to mention that while MPI was found to outcompete other investigated bats in the current study substantially, this does not invalidate their anticancer potential via other untested mechanistic routes. Identifying additional mechanisms by which these surprisingly long-lived animals combat cancer may allow us to devise new ways for humanity to follow suit.