# Ceramide-Rich Platforms Functionalize Gemcitabine Uptake

> **NIH NIH R01** · SLOAN-KETTERING INST CAN RESEARCH · 2024 · $384,644

## Abstract

Our data indicate that in select settings activation of acid sphingomyelinase (ASMase)/ceramide signaling in
tumor endothelial cells by radiation and certain chemotherapies synergizes with direct tumor cell damage to
impact outcome. ASMase is a lysosomal hydrolase preferentially expressed in endothelial cells up to 20-fold
compared with other mammalian cells. Mechanistically, endothelial ASMase activation leads within min to
formation of plasma membrane ceramide-rich platforms (CRPs), macrodomains that organize apoptotic signaling
programs. Support for our concept derives from studies showing xenografts of all histologies, when implanted in
asmase-/- host mice become resistant to gemcitabine, paclitaxel, etoposide, and high single dose radiotherapy,
effects reversed by exclusive adenoviral asmase gene delivery to tumor microvasculature. We recently
discovered VEGF is the principal inhibitor of endothelial ASMase, and that anti-angiogenic drugs de-repress
ASMase, amplifying tumor responses to anti-cancer therapies, but only under specific conditions. We found
irrespective of t1/2 or anti-angiogenic class, these drugs enhance endothelial apoptosis and tumor response only
if scheduled at 1-2h preceding chemotherapy, as ASMase can be de-repressed for only 1-2h. Based on these
data, the MSK Sarcoma Service performed a Phase II trial that showed sphingolipid-based timing of
bevacizumab vs. conventional synchronous timing improved metastatic sarcoma response to the cytidine
analogue gemcitabine from 38 to 93% (p=0.0024; Tap and Kolesnick, unpublished). The current application will
help establish the mechanism by which temporal delivery of a short-acting anti-angiogenic drug simultaneously
enhances gemcitabine-induced endothelial and tumor cell apoptosis. The overarching hypothesis of this
application is that the principal nucleoside transporter in mammalian cells, ENT1, required for gemcitabine
uptake, is not constitutively “on” as generally accepted but must insert into CRPs on endothelial and tumor cells
for functionalization. This new membrane-based mechanism of gemcitabine action will be explored in 3 aims
designed to examine mechanism of ENT1 functionalization via CRPs in both endothelial and sarcoma cells,
VEGF inhibition of ASMase-generated CRPs, and pharmacologic strategies to enhance endothelial ASMase-
ceramide signaling in vivo to improve ENT1-mediated gemcitabine uptake and cell death. A major concept to be
explored is that gemcitabine-induced ASMase secreted by endothelium triggers “bystander” gemcitabine uptake
via ENT1 in tumor cells. As such, these investigations potentially define failure to stimulate ASMase/ceramide
signaling as mediating a new form of chemoresistance. It is anticipated that information derived from studies
proposed here will inform a planned follow up clinical trial for advanced sarcoma to be performed by the Sarcoma
Service at MSK.

## Key facts

- **NIH application ID:** 10754234
- **Project number:** 5R01CA255336-04
- **Recipient organization:** SLOAN-KETTERING INST CAN RESEARCH
- **Principal Investigator:** Richard N Kolesnick
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $384,644
- **Award type:** 5
- **Project period:** 2021-01-01 → 2025-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10754234

## Citation

> US National Institutes of Health, RePORTER application 10754234, Ceramide-Rich Platforms Functionalize Gemcitabine Uptake (5R01CA255336-04). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10754234. Licensed CC0.

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