Loss-of-function mutations in glypican-3 (GPC3), one of the six mammalian glypicans, causes the Simpson-Golabi-Behmel overgrowth syndrome (SGBS), and GPC3 null mice display developmental overgrowth. Because the Hedgehog signaling pathway positively regulates body size, we hypothesized that GPC3 acts as an inhibitor of Hedgehog activity during development. Here, we show that GPC3 null embryos display increased Hedgehog signaling and that GPC3 inhibits Hedgehog activity in cultured mouse embryonic fibroblasts. In addition, we report that GPC3 interacts with high affinity with Hedgehog but not with its receptor, Patched, and that GPC3 competes with Patched for Hedgehog binding. Furthermore, GPC3 induces Hedgehog endocytosis and degradation. Surprisingly, the heparan sulfate chains of GPC3 are not required for its interaction with Hedgehog. We conclude that GPC3 acts as a negative regulator of Hedgehog signaling during mammalian development and that the overgrowth observed in SGBS patients is, at least in part, the consequence of hyperactivation of the Hedgehog signaling pathway.

Conservation, creation, and destruction of polarization in nuclear magnetic polarization-transfer experiments are discussed. In general, polarization is not conserved during NMR pulse experiments, although a useful reciprocity relation is formulated. The features of polarizationtransfer experiments are illustrated by liquid-and solid-state NMR.

Metastatic breast cancer is a major cause of death for women in the US, and breast cancers that metastasize to the brain have a particularly poor prognosis. To treat brain metastases of Her-2 positive breast cancers a number of Her-2 targeting drugs are now clinically available, including lapatinib, neratinib and tucatinib, among others. However, in part as a consequence of poor penetration of many drugs into the brain, combinations of standard chemotherapy plus targeted agent have only modest impact on progression free survival for such patients. We have developed preclinical models of human Her-2 positive breast cancer brain metastases to help address these issues. We selected human MDA-MD-361 and BT474 breast cancer cells lines by in vivo passaging in SCID mice, followed by molecular tagging of the derived variants (MDA361R and BT474R respectively), and then the stereotactic implantation of such cells into the brain of female SCID mice. Using luciferase-tagged BT474R we implanted 75,000 cells into the brains of the mice, and thereafter confirmed by luminescence the growth of the cells, which allowed for randomization of the mice to receive control saline (n=7), metronomic gemcitabine (100mg/kg/3days; i.p.; n=8), neratinib (40mg/kg/3 days; p.o.; n=7), or the combination of gemcitabine plus neratinib (n=8), which continued for 5 months largely in the absence of overt toxicity. The gemcitabine plus neratinib combination prolonged survival over the controls (150 days vs 65 days, p<0.5), although eventually all mice succumbed to disease. Tumors cells have been isolated from these therapy-administered mice for further characterization. Neratinib alone did not result in an increase in survival compared to controls, whereas metronomic gemcitabine improved survival but was inferior to the combination. We confirmed these findings using MDA361R tagged with human chorionic gonadotropin (hCG), which allows for the growth of cells to be monitored by assessment of hCG in the mouse urine, and these cells were implanted intracranially into female SCID mice. After urine hCG levels confirmed the presence of growing cells in the brain, the mice were randomized to the above 4 therapies (n=4/group), which showed an increase in survival of the combination compared to controls. These results point to intriguing effects of chemotherapy when used at continuous low (metronomic) doses, that in these studies involved gemcitabine administration every 3 days, and which in these models can be effectively combined with neratinib to suppress the growth of Her-2 positive breast cancer cells implanted into the mouse brain. These results highlight promising combination that could be used to suppress Her-2 positive breast cancer brain metastatic growth, and the developed models should facilitate the study of this subset of breast cancers. Citation Format: Serina Batson, Alejandro Sanchez, Hector M. Padilla, Diana L. Prospero, Brenda Lugo, Valeria V. Lopez, Daniella E. Estrada, Nydia De Avila, Saeedeh Darvishi, Arlene Levario, Shan Man, Ping Xu, Robert S. Kerbel, Guido Bocci, Giulio Francia. Metronomic gemcitabine plus neratinib effectively inhibits the growth of human Her-2 positive breast cancer cells intracranially implanted into immunodeficient mice. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3998.