PG545 enhances anti-cancer activity of chemotherapy in ovarian models and increases surrogate biomarkers such as VEGF in preclinical and clinical plasma samples
Introduction
Significant progress in understanding the molecular biology of epithelial ovarian cancer (OVCA), has not yet translated into improvements in disease outcomes. Most patients respond initially to therapy, however the majority relapse, making OVCA essentially incurable [1]. As a result, efforts are ongoing to identify novel agents that target the tumour microenvironment to impact angiogenesis, invasion and metastasis. While antiangiogenic therapy is emerging as a viable option for OVCA, other growth factors either remain functionally active or increase as a mode of resistance to anti-VEGF therapies [1]. The resistance mechanisms associated with the use of anti-VEGF therapies have been reported to include FGF-2 [2] and HB-EGF [3]. Therefore, a more effective treatment strategy would be to target key angiogenesis pathways simultaneously while reducing metastatic spread via inhibition of heparanase, an enzyme whose expression correlates with poor survival in metastatic gynaecological adenocarcinomas [4] and may contribute to the proliferation and metastasis of ovarian cancer [5]. Heparan sulfate proteoglycans (HSPG) play an important role in modulating heparan sulfate-binding growth factor (GF) signalling and heparanase activity [6], [7], in the extracellular matrix [8], and are implicated in angiogenesis and metastasis [9], [10], [11]. Thus, the development of therapeutics that inhibit these growth factors plus heparanase activity may have an advantage over existing antiangiogenic agents [12].
PG545 is a sulfated tetrasaccharide optimised for potency through the addition of a lipophilic moiety to attain potent in vivo activity, long plasma half-life and low anticoagulant potential [13], [14]. It inhibits angiogenesis via inhibition of VEGF and FGF-2 while preventing metastasis through blockade of heparanase [13], [15]. PG545 inhibits in vivo angiogenesis, attenuates tumour growth and/or metastasis in various cancer models including lung, hepatocellular, prostate, colon, melanoma, pancreatic and head and neck cancers [16], [17]. In a skin carcinogenesis model, PG545 inhibited the heparanase-dependent formation of tumour lesions providing further validation for the targeting of this enzyme in the development of cancer therapeutics [18]. It also reduced heparanase expression in a model of metastatic breast cancer [17]. However, PG545 activity in OVCA has not yet been studied. This is particularly relevant as previous investigations supporting the efficacy of anti-angiogenic agents in OVCA [19], [20], [21] would suggest an additional treatment benefit could be achieved with dual targeting of the angiogenic (VEGF) and metastatic (heparanase) pathways. Therefore, the aim of this study was to investigate the activity of PG545 in OVCA by, firstly, studying its impact on ovarian tumour cell growth, cellular migration and invasion, secondly, further define the molecular downstream signalling effects of PG545, and, thirdly, explore the impact of PG545 as a single agent and in combination with cytotoxic therapy in OVCA preclinical models. Finally, a preliminary assessment of putative biomarkers for PG545 activity was performed by analysing GFs and heparanase in the plasma samples from mice and a small cohort of advanced cancer patients treated with PG545 from a previous Phase I trial (ClinicalTrials.gov Identifier: NCT01252095). The safety and tolerability of intravenously-infused PG545 is currently being assessed in patients with advanced solid tumours (ClinicalTrials.gov Identifier: NCT02042781).
Section snippets
Cell culture
SKOV3, OV202, A2780, and ID8 cells were cultured as previously described [22], [23]. A2780 cells were obtained from Fox Chase Cancer Center and ID8 cells from Dr. Katherine Roby [24].
Growth factors & reagents
HB-EGF, HGF, FGF-2, VEGF, SDF-1, FGF-2, human recombinant VEGF165, stromal cell-derived factor-1 were purchased from R&D Systems (Minneapolis, MN). PG545 was synthesised by Progen Pharmaceuticals (Brisbane, QLD, Australia). All drugs (PG545, cisplatin (Calbiochem, Millipore, Billerica, MA), carboplatin (50 mg/5 ml,
PG545 inhibits OVCA cell viability in vitro as single agent and in combination with chemotherapeutic agents
The potential of PG545 to synergise with the chemotherapeutic agents cisplatin and paclitaxel against OVCA cells was investigated using cell viability assays. Firstly, we showed that PG545 exhibited concentration-dependent growth inhibition (Supplementary Fig. 1A and D) in A2780 and SKOV3 cell lines. In combination with cisplatin or paclitaxel, PG545 at 10 μM increased the cytotoxic effect of cisplatin or paclitaxel over a range of concentrations in A2780 and SKOV3 cell lines (Supplementary Fig.
Discussion
Multiple clinical trials have demonstrated efficacy of the antiangiogenic drug bevacizumab, in the treatment of advanced OVCA [19], [20], [21]. However, despite initial responses, once bevacizumab treatment was stopped, most patients recurred which resulted in bad prognosis. Genomic and molecular complexity of epithelial OVCA and its ability to metastasise via multiple routes (intraperitoneal, hematogenous, lymphatic) might contribute to some of the resistance against single target anti
Role of funding source
The work conducted by the laboratory head Dr. Viji Shridhar is supported in part by the grants from the National Institutes of Health CA123249, and Minnesota Cancer Alliance (MOCA) to (VS) and Gynecologic Oncology Fellowship fund to (BW) from the Department of Obstetrics and Gynecology at Mayo Clinic.
Conflict of interest statement
Edward Hammond, Keith Dredge and Darryn Bampton are employed by, or act as consultants for Progen Pharmaceuticals, which developed PG545. None of the other authors have any conflicts of interest.
Acknowledgements
The authors wish to acknowledge the technical assistance of Jacie Maguire, Takayo Ota, Jenifer Baranski, Erin Trachet (Charles River Discovery Service, Morrisville, NC), Kay Meshaw (Charles River Discovery and Imaging Services, Ann Arbor, MI) on the A2780 s.c. model, Ralf Brandt (vivoPharm, Bundoora,, VIC, Australia) for the SKOV3 model, Maree Smith, Debra Siebert and Linda Wright (TetraQ, Brisbane, Australia) for the bioanalysis of the PG545 samples.
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2020, Biochemical PharmacologyCitation Excerpt :In the PG500 series, the selected lead compound PG545 (pixatimod) consisted of a synthetic fully sulfated tetrasaccharide functionalized with a lipophilic cholestanyl aglycone. It exhibited long plasma half-life, low anticoagulant activity and a remarkable capability to reduce FGF2-induced migration of ovarian carcinoma cells [98]. In a series of synthetic HS oligosaccharides with different length and sulfation, the 12-mer 2SNS oligosaccharide emerged as the most active in counteracting FGF2 functions in competition and cell-based assays [99].
Models of ovarian cancer to test new agents
2020, Overcoming Ovarian Cancer ChemoresistanceTargeting Heparanase in Cancer: Inhibition by Synthetic, Chemically Modified, and Natural Compounds
2019, iScienceCitation Excerpt :Moreover, PG545 suppressed Wnt/β-catenin signaling by interacting with Wnt3a and Wnt7a in pancreatic tumor xenografts (Jung et al., 2015). In another advancement, PG545 in combination with paclitaxel significantly reduced tumor burden in human ovarian carcinoma model (A2780 model), supporting clinical testing of PG545 alone or in combination with other chemotherapeutic agents in patients with ovarian cancer (Winterhoff et al., 2015). Vlodavsky and Pass have recently reported (Barash et al., 2018) that PG545 markedly attenuated mesothelioma tumor growth.
Dynamic matrisome: ECM remodeling factors licensing cancer progression and metastasis
2018, Biochimica et Biophysica Acta - Reviews on CancerCitation Excerpt :Additionally, PG545 treatment resulted in an accumulation of macrophages in the tumor periphery suggesting a role for HEP inhibition in altering tumor immunity. Other groups reported PG545 to be effective either alone or in combination with chemotherapy drugs (gemcitabine, carboplatin, or paclitaxel), in reducing the growth of orthotopically injected xenografts generated using ovarian [287] or pancreatic [288] cancer cell lines. Another HEP inhibitor, SST0001, demonstrated superior results in vivo by inhibiting the growth of subcutaneously injected multiple myeloma cells [289], orthotopic pancreatic tumors [290] and pediatric sarcomas [291,292].
Circulating syndecan-1 is associated with chemotherapy-resistance in castration-resistant prostate cancer
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These authors contributed equally to this work.
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Current address: Department of Obstetrics, Gynecology and Women’s Health, University of Minnesota, USA.