Abstract P2-04-04: Developing targeted therapeutic microbubbles for enhanced epigenetic drug delivery for breast cancer
Authors: Alataki A , Abou-Saleh R , McLaughlan JR , Markham AF , Evans SD , Coletta PL , Valleley EM 
Published: February 2018

Abstract
Background: In recent years, there has been great interest in developing drugs that modify epigenetic changes as new therapies for breast cancer (BC). There is evidence that aberrant epigenetic inactivation of genes, essential for normal cell growth, is involved in cancer. These modifications are potentially reversible therefore re-activation of genes in response to epigenetic drugs can result in inhibition of tumour growth or sensitisation to other anti-cancer therapies. Epigenetic drugs are in clinical trials for BC but have some drawbacks: while some can be highly effective in vitro, their poor stability could compromise their clinical use. Also, high doses required to induce an effect in patients could increase off-site toxicity. As a result there is an urgent need to develop novel systems for the delivery and release of these drugs.
Objectives: Our aim is to develop targeted microbubbles (MBs) to enhance therapeutic effects in vitro and in vivo. Ultrasound (US)-mediated drug delivery using MBs is proposed as a non-invasive approach for localised drug administration.
Methods: We developed assays using low doses of a DNA methyltransferase inhibitor, called decitabine (DAC), for determining its delivery and effect in vitro and in vivo. VEGFR2 was assessed as a targeting molecule for therapeutic delivery to tumour vasculature in vitro and in a human BC xenograft model. We have generated therapeutic MBs with DAC using a flow-focussing microfluidic platform and conducted in vitro and currently performing in vivo studies to observe tumour and tissue responses.
Results: Treatment of triple-negative BC (TNBC) cells with low DAC doses revealed restoration of epigenetically dysregulated tumour suppressor genes. These genes were used as biomarkers for the assessment of DAC effects in a human TNBC mouse model. To evaluate the use of a targeting molecule for drug delivery, specific binding of VEGFR2-targeted MBs on VEGFR2+ve mouse endothelial cells was verified by a flow assay. VEGFR2 expression was assessed longitudinally in xenograft tissue and demonstrated significantly higher VEGFR2 expression in the vasculature of smaller size tumours, indicating the time that delivery of targeted MBs would be most effective. DAC-loaded liposomes or co-administration of DAC and MBs in combination with US using a specifically designed US transducer, were tested in vitro. Currently, investigation of the potential of US-triggered drug delivery enhancing efficacy of DAC in vivo is being carried out. In addition, combination treatments have been performed in vitro, showing increased sensitisation of cells to anthracycline treatment after priming with DAC.
Conclusions: It may be feasible to combine US, MBs and epigenetic therapy in a pre-clinical setting to improve drug efficacy, particularly for drugs that are rapidly degraded within the body. MB delivery may have the potential to reduce the dosage required, thus reducing off-site side effects in patients.
Citation Format: Alataki A, Abou-Saleh R, McLaughlan JR, Markham AF, Evans SD, Coletta PL, Valleley EM. Developing targeted therapeutic microbubbles for enhanced epigenetic drug delivery for breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-04-04.