Improving the anti-tumour efficacy of Albendazole

Albendazole (ABZ) is a benzamidazole derivative that binds to β-tubulin and inhibits the polymerisation of microtubules. ABZ has a remarkable activity against a variety of tumour cell lines including colorectal, liver, and ovarian cancer cells. In pre-clinical models, ABZ has been shown to have both anti-tumour and anti-angiogenic activities. Nevertheless, poor aqueous solubility of ABZ limits its absorption, and as a result, its efficacy. Therefore, the first aim of this project was to improve the aqueous solubility of ABZ. Using a combination of ionisation with acid and complexation with hydroxypropyl-β-cyclodextrin (HPβCD), a relatively high concentration of ABZ in solution was achieved. Comparison of pharmacokinetic profiles of ABZ/HPβCD with a conventional formulation of ABZ in hydroxypropyl methylcellulose (ABZ/HPMC) in nude mice revealed that complexation with HPβCD results in a significantly higher peak plasma concentration (Cmax) and area under the curve (AUC) of ABZ and its metabolites. Moreover, in mice-bearing human colorectal cancer cells, HCT-116, ABZ/HPβCD treatment led to a significant delay in tumour growth with increase in survival of animals as compared with vehicle and ABZ/HPMC treatments.The second aim of this research was to improve the efficacy of ABZ using combination therapy. To this end, the interaction between ABZ and different chemotherapeutic agents were assessed using the Sulforhodamine B assay (SRB) and quantified by median effect analysis method. Among the tested agents, a synergistic anti-proliferative effect was observed with the combination of ABZ and 2-methoxyestradiol (2ME) in HCT-116 and DU145. Of interest, 2ME, a microtubule targeting agent binds to similar colchicine-binding site of β-tubulin as ABZ and inhibits microtubules polymerisation. Synergistic interaction of ABZ and 2ME was accompanied with the activation of extrinsic pathway of apoptosis.In vivo, the combination of low concentration of ABZ with 2ME resulted in an increase in the survival rate of mice-bearing HCT-116 tumours. This effect was accompanied by a decrease in plasma and tumour vascular endothelial growth factor (VEGF) as well as a reduction in microvessel density. In addition, combination therapy led to a significant decrease in proliferation rate of the tumour and an increase in apoptosis. Noticeably, high concentration of ABZ, in combination with 2ME, resulted in an antagonistic effect on tumour growth and survival of the animals. Taken together, the solubility and anti-tumour efficacy of ABZ was highly increased by complexation with HPβCD, leading to the conclusion that the formulation may be suitable for parenteral administration. Moreover, combination of ABZ and 2ME has shown promising results in pre-clinical model. Additionally, the finding that the combination of two microtubule-binding agents that share the same binding site can act synergistically in vitro and in vivo may lead to the development of new therapeutic strategies in cancer treatment

Abstract LB-007: Synergistic inhibition of human gastric and colorectal cancers by Bromelain and N-acetylcysteine: An in vivo study

Abstract Mucin is well understood to be an adverse prognostic factor in some cancers. We previously reported that a combination of Bromelain (BR) and N-acetylcysteine (NAC) were synergistic in dissolving pseudomyxoma peritonei mucin, had direct in vitro cytotoxic effects on some gastrointestinal cancer cells and sensitized them to some chemotherapy agents. In the present study, we aimed to evaluate the growth-inhibitory effect of BR and NAC as single agent or combination therapy in nude mice models of gastrointestinal cancer. Nude mice received 2 million and 1 million cells of MKN45 (gastric) and LS174T (colorectal) by intraperitoneal injection. At day 14 and 7 post inoculation for MKN45 and LS174T cells, respectively, animals were intraperitoneally administrated BR (3, 6 mg/kg), NAC (300, 500 mg/kg) or their combination every other day over 12 days for MKN45 and 17 days for LS174T models. At the end of the study, the animals were euthanized, the number of peritoneal nodules and their weight were collected, and the peritoneal tumors were subjected to immunohistochemistry for evaluation of MUC2. No toxicity was observed during the experiment. At necropsy, highly significant reductions in the number of tumor nodules and tumor burden were observed, in particular in the combination group, where almost complete inhibition in LS174T group was found. There was more than 95% and 70% decreases in tumor burden and tumor nodules, respectively, in LS174T group after combination treatment. For MKN45 model, the reductions in tumor burden and tumor nodules in combination groups were more than 60% and 70%, respectively. Performing immunohistochemistry on tumor samples, MUC2 staining of the LS174T xenografts showed a greater than 60% reduction of cytoplasmic staining. To the best of our knowledge, this is the first report of the in vivo use of this combination with synergistic inhibition of human gastric and colorectal cancers. The combination of BR and NAC in mucin secreting gastrointestinal tumors is interesting and could be of potential value in peritoneal cancer. Citation Format: Afshin Amini, Samar Masoumi-Moghaddam, Anahid Ehteda, Winston Liauw, Javed Akhter, Krishna Pilai, David L. Morris. Synergistic inhibition of human gastric and colorectal cancers by Bromelain and N-acetylcysteine: An in vivo study. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-007. doi:10.1158/1538-7445.AM2015-LB-007</jats:p

DIPG-14. TARGETING POLO-LIKE KINASE 1 IN COMBINATION WITH KEY ONCOGENIC DRIVERS IN DIPG: FROM SINGLE AGENT TO COMBINATION STRATEGIES

Abstract Diffuse Intrinsic Pontine Glioma (DIPG) are devastating paediatric brainstem tumours. Loss of function mutations in DIPG decrease genetic stability and impair DNA damage response pathways promoting tumourigenesis. Polo-like Kinase 1 (PLK1) is a pivotal controller of cell growth, regulating key intermediaries of DNA replication, homologous repair, the cell cycle and cell division. We have found DIPG cultures consistently overexpress PLK1 with inhibition resulting in decreased tumour cell growth, heightened cell cycle arrest and apoptosis. Single agent treatment using PLK1 inhibitors unprecedentedly doubled the median survival of animals harbouring DIPG tumours. Through gene expression analysis, we’ve showed PLK1 inhibition affected multiple pathways which control the cell cycle, cell death regulation, microtubule organization and regulation of cell migration. We found these pathways of differentially expressed genes were significantly enriched for known targets of both E2F1 and E2F4. Analysis of gene expression and proteomic studies also revealed PLK1 inhibition decreased the activation and expression of key tumour promoting mediators within multiple phases of the cell cycle, decreased expression of tumour promoters including MYC and the PI3K/mTOR pathway and reactivated tumour suppressors p53 and PTEN. Assessing these changes in the treated transcriptome and proteome, we aim to develop multiple potentially translatable combination treatment strategies for DIPG. We have performed mechanistic studies and identified synergism with PLK1 inhibitors and the epigenetic regulator panobinostat, bet/bromodomain inhibitor JQ1, dual PI3K/mTOR inhibitor bimiralisib and PI3K inhibitor BKM120. Finally, we found PLK1 inhibitors act as potent radiosensitizers, enhancing the therapeutic effects of radiotherapy in vitro and in vivo.</jats:p