Targeting of Hsp32 in Solid Tumors and Leukemias: A Novel Approach to Optimize Anticancer Therapy (Supplementry Material)

Abstract

Heat shock protein 32 (Hsp32), also known as heme oxygenase-1 (HO-1), is a stress-related anti-apoptotic molecule, that has been implicated in enhanced survival of neoplastic cells and in drug-resistance. We here show that Hsp32 is expressed in most solid tumors and hematopoietic neoplasms and may be employed as a new therapeutic target as evidenced by experiments using specific siRNA and a Hsp32-targeting pharmacologic inhibitor. This Hsp-32 targeting drug, SMA-ZnPP, was found to inhibit the proliferation of neoplastic cells with IC(50) values ranging between 1 and 50 microM. In addition, SMA-ZnPP induced apoptosis in all neoplastic cells examined. Furthermore, SMA-ZnPP was found to synergize with other targeted and conventional drugs in producing growth-inhibition. Resulting synergistic effects were observed in all tumor and leukemia cells examined. Interestingly, several of the drug partners, when applied as single agents, induced the expression of Hsp32 in neoplastic cells, suggesting that synergistic effects resulted from SMA-ZnPP-induced ablation of a Hsp32-mediated survival-pathway that is otherwise used by tumor cells to escape drug-induced apoptosis. Together, Hsp32 is an important survival factor and target in solid tumors and hematopoietic neoplasms, and may be used to optimize anticancer therapy by combining conventional or targeted drugs with Hsp32-inhibitors. Based on these data, it seems desirable to explore the value of Hsp32-targeting drugs as anti-cancer agents in clinical trials.

Heme Oxygenase-1 Promoter Polymorphism is a Predictor of Disease Relapse in Pancreatic Neuroendocrine Tumors

“…Several studies have shown that in different tumors the role of HO-1 as to tumor development and progression is distinct [29][30][31][32][33]. Interestingly, Yamaya et al have reported SGTn allele to be associated with longevity in healthy Japanese [34].…”

Targeting of Leukemia-Initiating Cells to Develop Curative Drug Therapies: Straightforward but Nontrivial Concept

“…Multidrug resistance genes have also been described to play a role in LSC in AML [67]. Further mechanisms underlying intrinsic resistance of LSC may be an abnormal expression or upregulation of survivalrelated molecules (often stress-related or after drug exposure), abnormal expression of signalling molecules or transcription factors, and the lack/loss of death regulators [56][57][58][59][60][61]68,69] (Table 2). In addition, the local organ-specific microenvironment, tissue hypoxia, and the interaction with the ´stem cell niche´ (LSC-related microenvironment) may contribute to resistance of LSC [70][71][72].…”

HO-1/CO system in tumor growth, angiogenesis and metabolism — Targeting HO-1 as an anti-tumor therapy

“…Inhibitors of heme oxygenases CrMP and CrPP -the highest activity (IC 50 below 0.1 μM), the highest specificity against HO-1  SnPP -still potent, but less active (IC 50 = 0.1 µM for HO-2, 0.47 µM for HO-1, hence more specific against HO-2)  ZnPP -IC 50 = 2.65 µM for HO-2 and 5.45 µM for HO-1 -hence more specific against HO-1 than SnPP  Other: SnDP, SnMP, ZnDP, ZnBG  None is selectively specific for HO-1  Photosensitizing effects  Inhibition of: nitric oxide synthase, soluble guanylyl cyclase, cytochrome P450  Limited bioavailability  Induction of HO-1 expression  Direct binding to DNA through purinerich regions  Only SnPP and SnMP tested in limited clinical studies[145], reviewed in[115]  ZnPP  PEG-ZnPP -water soluble; claimed more available  SMA-ZnPP -water soluble; higher and more efficient intracellular uptake; but similar inhibition of HO-1 as PEG-ZnPP  The same as for other metalloporphyrins  Inhibition of IDO  Inhibition of cyclin D1  Inhibition of WNT/beta-catenin  Inhibition of angiogenic genes like Ang1, HGF, Flt-1, IGF-1, Met, FGF-2R  No clinical studies[117,121,125,126,146]  Water soluble in contrast to metalloporphyrins  Non-competitive (unlike metalloporphyrins)  Not specific for HO-1A C C E P T E D M A N U S C R I P T Some much more specific against HO-1 than HO-2  Shown to be active against experimental tumors (e.g. Can inhibit cytochrome P450  Not tested in clinical studies (but…”