Use of a Glycolipid Inhibitor to Ameliorate Renal Cancer in a Mouse Model

<div><p>In a xenograft model wherein, live renal cancer cells were implanted under the kidney capsule in mice, revealed a 30-fold increase in tumor volume over a period of 26 days and this was accompanied with a 32-fold increase in the level of lactosylceramide (LacCer). Mice fed D- threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP), an inhibitor of glucosylceramide synthase and lactosylceramide synthase (LCS: β-1,4-GalT-V), showed marked reduction in tumor volume. This was accompanied by a decrease in the mass of lactosylceramide and an increase in glucosylceramide (GlcCer) level. Mechanistic studies revealed that D-PDMP inhibited cell proliferation and angiogenesis by inhibiting p44MAPK, p-AKT-1 pathway and mammalian target for rapamycin (mTOR). By linking glycosphingolipid synthesis with tumor growth, renal cancer progression and regression can be evaluated. Thus inhibiting glycosphingolipid synthesis can be a bonafide target to prevent the progression of other types of cancer.</p></div

D-PDMP reduced tumor volume in mice.

<p>Mice (BALB/C) were pre-anesthetized and RENCA tumor cell suspension (10⁶ cells) was injected in the subcapsular space of the left kidney. Experimental treatment began two days after subcapsular tumor implantation. Mice fed by oral gavage D-PDMP (3 and 10 mg/kg body weight, MPK) daily. D-PDMP was solubilized in 5% Tween-80 in saline. Placebo mice received the vehicle (5% Tween-80 in saline 100 µl only). After 26 days, the mice were sacrificed. The right kidney served as control, and the left kidney served as placebo or drug treated with 3 and 10 MPK of D-PDMP. <b>A</b>: A marked increase in mouse kidney tumor volume is sharply decreased by feeding D-PDMP. <b>B</b>. D-PDMP (3 and 10 MPK) did not reduce total body weight in mice. <b>C</b>: The level of D-PDMP in kidney of mice treated with 3 and 10 MPK of D-PDMP were similar.</p

D-PDMP treatment altered the levels of several sphingolipids but not sphingomyelin in mice renal cancer.

<p>The level of various sphingolipids were measured by tandem LC-MS/MS. <b>A</b>: D-PDMP decreased the level of ceramide, <b>B</b>: ceramide-1-phosphate, and <b>D</b>: sphingosine-1-phosphate. D-PDMP modestly increased the level of sphingosine; <b>C</b>, <b>E</b>: sphinganine and <b>F</b>: monohexosylceramide. <b>G</b>: D-PDMP dose-dependently decreased the level of dihexosylceramide in mice renal cancer. <b>H</b>: D-PDMP did not change the level of sphingomyelin in mouse renal cancer. (* p<.05, **p<.01 N = 4).</p

D-PDMP decreased the activity of glycosyltransferases and glycohydrolase in mouse renal cancer.

<p>Measurement of lactosylceramide synthase activity in mouse kidney was conducted using UDP[14C] galactose as galactose donor and GlcCer as the acceptor, as detailed <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0063726#pone.0063726-Chatterjee3" target="_blank">[11]</a>. We observed that feeding D-PDMP dose-dependently decreased the activity of this enzyme <b>A</b>: glucosylceramide synthase activity was decreased to the same extent irrespective of whether 3 MPK or 10 MPK of D-PDMP was fed to mice with renal cancer, <b>B</b>: glucosylceramidehydrolase activity was decreased by D-PDMP treatment and <b>C</b>: lactosylceramide synthase activity was dose-dependently decreased in D-PDMP fed mice with renal cancer (N = 4; *p<.05).</p