SQAP (sulfoquinovosylacylpropanediol), a lipid-based radiosensitizer commercialized as Lavurchin, showed no direct cytotoxicity against canine hemangiosarcoma cells in vitro but significantly suppressed tumor growth in three patient-derived xenograft models. This suggests its anti-tumor activity comes not from killing HSA cells but from remodeling the tumor microenvironment around them.
Researchers at Hokkaido University transplanted surgically resected splenic hemangiosarcoma tissue from three dogs into immunocompromised mice and treated the resulting tumors with SQAP at two dose levels. Both doses suppressed growth significantly across all three models, with no difference between them. Gene expression analysis showed far more SQAP-responsive transcriptional changes in mouse host cells surrounding the tumor than in the canine tumor cells themselves, with enrichment in pathways related to angiogenesis, hypoxia, and stromal remodeling.
In two of three models, SQAP reduced host-derived blood vessel density and increased smooth muscle coverage of remaining vessels, consistent with a shift toward more structurally mature vasculature. Hemangiosarcoma is an endothelial cancer that forms chaotic vascular structures to sustain itself, making vascular remodeling a relevant mechanism. SQAP also altered macrophage-associated marker profiles in and around tumors, though the direction varied by model — consistent with the known role of tumor-associated macrophages in HSA progression but not yet well enough characterized to draw firm conclusions.
The study is preclinical and exploratory. The mice were immunocompromised, so SQAP’s interaction with a functioning immune system remains untested. Structural vascular changes were measured but functional perfusion was not, and the response varied across models.
Prior work on SQAP has shown it can enhance both radiation and chemotherapy response in other cancer types, and a recent paper demonstrated it interferes with DNA repair pathways in canine cancer cells. Whether SQAP combined with radiation or doxorubicin would improve outcomes in hemangiosarcoma has not been tested.
