NAD Synthesis Pathway Interference Is a Viable Therapeutic Strategy for Chondrosarcoma

Abstract

Nicotinamide phosphoribosyltransferase (NAMPT) and nicotinic acid phosphoribosyltransferase (NAPRT) are rate-limiting enzymes in the NAD synthesis pathway. Chondrosarcoma is a malignant cartilage forming bone tumor, in which mutations altering isocitrate dehydrogenase-1 and -2 (IDH1 and IDH2) activity have been identified as potential driver mutations. Vulnerability for NAD depletion has been reported for -mutant cells. Here, the potency of NAMPT inhibitors as a treatment of chondrosarcoma was explored. Eleven chondrosarcoma cell lines were treated with NAMPT inhibitors, in which the effect on cell viability, colony formation, and 3D collagen invasion was assessed. The expression level of NAMPT and NAPRT transcripts in chondrosarcoma cells was determined by qRT-PCR. Methylation of the NAPRT promoter was evaluated using a previously published dataset of genome-wide methylation. In addition, a methylation dataset was used to determine methylation of the NAPRT promoter in 20-mutated cartilage tumors. Chondrosarcoma cells showed a dose-dependent decrease in cell viability, 3D collagen invasion, and colony formation upon treatment with NAMPT inhibitors, in which nearly half of the cell lines demonstrated absolute ICs in the low nanomolar range. Increasing ICs correlated to increasing NAPRT expression levels and decreasing NAPRT promoter methylation. No correlation between mutation status and sensitivity for NAMPT inhibitors was observed. Strikingly, higher methylation of the NAPRT promoter was observed in high-grade versus low-grade chondrosarcomas. In conclusion, this study identified NAMPT as a potential target for treatment of chondrosarcoma. Chondrosarcoma patients, especially those of high histologic grade with lower expression and hypermethylation of NAPRT, may benefit from inhibition of the NAD synthesis pathway. .

NAD- and NADPH-Contributing Enzymes as Therapeutic Targets in Cancer: An Overview

“…In vitro studies have shown promising results using a NAMPT inhibitor in cancer cells, especially the IDH1/2 mutant cancer cell lines (Table 1). MGG119, MGG152, BT142 primary glioblastoma cell lines; HT1080, 30T and SW1353 chondrosarcoma cell lines; SNU484, SNU668, SNU1750, MKN1 and Hs746T gastric cancer cell lines which have mutations in IDH1 [7][8][9], were sensitive to NAMPT inhibition. NAMPT inhibitors not only have shown promising effect as single-agent therapy, but were also found to sensitize other modalities of cancer treatment in both in vitro and in vivo experiments [45,[55][56][57], as shown in Tables 2 and 3.…”

“…IDH mutations have been associated with several cancers, in particular, WHO grade II/III and secondary glioblastoma multiforme (GBM), acute myeloid leukemia (AML), intrahepatic cholangiocarcinoma, gastric cancer and cartilaginous tumors [9,[82][83][84][85]. Most of mutant IDH1 tumors have a single, missense mutation at codon 132 that changes arginine to histidine (IDH1 R132H ).…”

“…On the other hand, nicotinate phosphoribosyltransferase (NAPRT) also produces NAD through the nicotinic acid pathway [1,6]. However, recent studies have shown that isocitrate dehydrogenase (IDH) mutations may result in downregulation of NAPRT [7][8][9].…”

“…CpG islands or loss of exon 1 expression in NAPRT [7][8][9]39,40]. As a consequence, inhibition of NAPRT enzyme activity forces these cells to mainly depend on the NAD salvage pathway to generate NAD ( Figure 1) [7].…”

Is the IDH Mutation a Good Target for Chondrosarcoma Treatment?

“…Glutaminolysis and NAD synthesis pathways are potentially other vulnerable targets in the context of IDH mutated chondrosarcomas, but their clinical applications remain to be determined [46,47].…”