Impact of heparanase‐2 (Hpa2) on cancer and inflammation: Advances and paradigms.

HPSE2, the gene‐encoding heparanase 2 (Hpa2), is mutated in urofacial syndrome (UFS), a rare autosomal recessive congenital disease attributed to peripheral neuropathy. Hpa2 lacks intrinsic heparan sulfate (HS)‐degrading activity, the hallmark of heparanase (Hpa1), yet it exhibits a high affinity toward HS, thereby inhibiting Hpa1 enzymatic activity. Hpa2 regulates selected genes that promote normal differentiation, tissue homeostasis, and endoplasmic reticulum (ER) stress, resulting in antitumor, antiangiogenic, and anti‐inflammatory effects. Importantly, stress conditions induce the expression of Hpa2, thus establishing a feedback loop, where Hpa2 enhances ER stress which, in turn, induces Hpa2 expression. In most cases, cancer patients who retain high levels of Hpa2 survive longer than patients bearing Hpa2‐low tumors. Experimentally, overexpression of Hpa2 attenuates the growth of tumor xenografts, whereas Hpa2 gene silencing results in aggressive tumors. Studies applying conditional Hpa2 knockout (cHpa2‐KO) mice revealed an essential involvement of Hpa2 contributed by the host in protecting against cancer and inflammation. This was best reflected by the distorted morphology of the Hpa2‐null pancreas, including massive infiltration of immune cells, acinar to adipocyte trans‐differentiation, and acinar to ductal metaplasia. Moreover, orthotopic inoculation of pancreatic ductal adenocarcinoma (PDAC) cells into the pancreas of Hpa2‐null vs. wild‐type mice yielded tumors that were by far more aggressive. Likewise, intravenous inoculation of cancer cells into cHpa2‐KO mice resulted in a dramatically increased lung colonization reflecting the involvement of Hpa2 in restricting the formation of a premetastatic niche. Elucidating Hpa2 structure–activity‐relationships is expected to support the development of Hpa2‐based therapies against cancer and inflammation. [ABSTRACT FROM AUTHOR]