A nuclear-directed human pancreatic ribonuclease (PE5) targets the metabolic phenotype of cancer cells

Abstract

Ribonucleases represent a new class of antitumor RNA-damaging drugs. However, many wild-type members of the vertebrate secreted ribonuclease family are not cytotoxic because they are not able to evade the cytosolic ribonuclease inhibitor. We previously engineered the human pancreatic ribonuclease to direct it to the cell nucleus where the inhibitor is not present. The best characterized variant is PE5 that kills cancer cells through apoptosis mediated by the p21(WAF1/CIP1) induction and the inactivation of JNK. Here, we have used microarray-derived transcriptional profiling to identify PE5 regulated genes on the NCI/ADR-RES ovarian cancer cell line. RT-qPCR analyses have confirmed the expression microarray findings. The results show that PE5 cause pleiotropic effects. Among them, it is remarkable the down-regulation of multiple genes that code for enzymes involved in deregulated metabolic pathways in cancer cells.

Keywords: antitumor drug; human pancreatic ribonuclease; metabolism of cancer cells; microarray profiling; tumor cell death.

Figure 1. PE5 down-regulated enzymes belonging to deregulated metabolic pathways in cancer

Green, name of the enzymes down-regulated by PE5; blue, metabolites that are the main source of energy for cancer cells depending on their status; blue arrows, catabolic pathways; blue dashed arrows, potential gluconeogenesis not still proved in cancer cells (see text for more details); red arrows, biosynthetic pathways critical for cancer cell grow and division; PPP, pentose phosphate pathway; TCA, tricarboxylic acid; G6P, glucose-6-phosphate; OAA, oxaloacetate; PEP, phosphoenolpyruvate; 2PG, 2-phosphoglycerate; 3PG, 3-phosphoglycerate; HMG-CoA, 3-hydroxy-3-methylglutaryl-coenzyme A; R5P, ribose-5-phosphate. Enzymes: ACACA, acetyl-CoA carboxylase alpha; ACAT, acetyl-CoA acetyltransferase; ACL, ATP citrate lyase; ASAH1, N-acylsphingosine amidohydrolase (acid ceramidase) 1; DHCR24, 24-dehydrocholesterol reductase; ENO1, enolase 1, (alpha); FASN, fatty acid synthase; GPT, alanine aminotransferase; G6PD, glucose-6-phosphate dehydrogenase; HADHA, hydroxyacyl-CoA dehydrogenase/3-ketoacyl-CoA thiolase/enoyl-CoA hydratase (trifunctional protein), alpha subunit; HMGCR, HMG-CoA reductase; HMGCS, HMG-CoA synthase; IDH2, isocitrate dehydrogenase 2 (NADP+), mitochondrial; LDHA, lactate dehydrogenase A; LPL, lipoprotein lipase; MDH1, malate dehydrogenase 1, NAD (soluble); MDH2, malate dehydrogenase 2, NAD (mitochondrial); ME1, malic enzyme 1, NADP+-dependent, cytosolic; ME3, malic enzyme 3, NADP+-dependent, mitochondrial; MSMO1, methylsterol monooxygenase 1; PC, pyruvate carboxylase; PCCB, propionyl CoA carboxylase, beta polypeptide; PCK2, phophoenolpyruvate carboxykinase 2 (mitochondrial); PDH, pyruvate dehydrogenase complex; PGAM1, phosphoglycerate mutase 1 (brain); PGM1, phosphoglucomutase 1, PHGDH, phosphoglycerate dehydrogenase; PK, pyruvate kinase; PSAT1, phosphoserine aminotransferase 1; SPTLC3, serine palmitoyltransferase, long chain base subunit 3; TM7SF2, transmembrane 7 superfamily member 2.

Figure 2. Potential links between PE5 down-regulated oncogenes and up-regulated tumor suppressors and deregulated metabolic pathways through signaling pathways

The PE5 down-regulated oncogenes and the PE5 up-regulated tumor suppressors are shown in the blue boxes while the potential signaling pathways are indicated in the empty boxes. The deregulated metabolic pathways are inhibited by both the down-regulation of the oncogenes and the up-regulation of the tumor suppressor (see text for more details). Genes: BCL2L11, BCL2-like 11 (apoptosis facilitator); CLU, clusterin; MET, met proto-oncogene (hepatocyte growth factor receptor); MXD1, MAX dimerization protein 1; NFKBIA, nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha; TGM2, transglutaminase 2 (C polypeptide, protein-glutamine-gamma-glutamyltransferase); WWOX, WW domain containing oxidoreductase.