Abstract 4890: In silico study of enzymes involved in heparan sulfate catabolic process in cancer resistant mammals
Authors: Payet Fabrizio Oliveri , Rivero Claudia Machicado 
Published: March 2024

Abstract
Some mammals such as elephants, bats, whales, and blind mole rats (Spalax) are resistant to cancer. One of the cancer protective mechanisms present in such species includes a reduced degradation of heparan sulfate (HS), an important component of the extracellular matrix (ECM), present in Spalax. Such effect occurs due to a splicing variant of heparanase, called variant 36, that lacks enzymatic activity. Consequently, both HS and ECM are very stable in Spalax’s tissues. If HS is stabilized, in cancer resistant mammals, due to the decrease of heparanase or other enzymes involved in HS catabolic process is unknown. We studied total of 9 enzymes (HPSE2, GusB, IDUA, IDS, NAGLU, SGSH, GNS, Sulf-2, HGSNAT) that regulate HS catabolism and homologs in 9 mammals. Multiple sequence alignments were done by MEGA to identify substitutions present in cancer resistant species in comparison with cancer susceptible animals. Such amino acid variants were further analyzed and both their energy stability and their functional effects were predicted by using online in silico tools including MAESTROweb, Condel, PANTHER, REVEL, and CADD. Finally, homologs with deleterious predicted variants were modelled with SWISSMODEL and their 3D structures were analyzed with Pymol and ChimeraX to identify structural features likely related to its loss of function. We found two loss of function missense variants, K264Q and W626L, in Alpha-L-iduronidase (IDUA) of Spalax. In addition, most of Brandt's bat enzymes and the N-sulphoglucosamine sulphohydrolase (SGSH) of the bowhead whale were very energy destabilizing enzymes with positive and higher ΔΔG values compared to human homologs. In the other hand, although some catalytic residues in the study enzymes are conserved in cancer resistant animals, their spatial arrangement and conformation in the 3D structure are different compared to human homologs, including E182 of IDUA which is one of the catalytic residues. In general, the secondary structure is conserved across the 9 enzymes studied but some differences were observed in cancer resistant animals including one of the beta strands near the catalytic domain in human and mice IDUA that appears as a loop in Spalax. In summary, HS stabilization could raise in cancer resistant mammals through the existence of lack of enzymatic activity not only in heparanase but also in other enzymes that participate in HS catabolic process, via a set of loss of function variants and changes in secondary and tertiary structure as well as a reduction of energy stabilization. More interestingly, such mechanism could be present in other cancer resistant mammals such as bats and bowhead whales. This study demonstrates that computational approaches are useful to study biological mechanisms of cancer resistance present in some mammals. This knowledge could be translated to humans and HS catabolic process could offer a new source of therapeutic anticancer targets.
Citation Format: Fabrizio Oliveri Payet, Claudia Machicado Rivero. In silico study of enzymes involved in heparan sulfate catabolic process in cancer resistant mammals [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4890.