Drug-Loaded Nanomicelles Conjugated To Mucin Antibodies For Direct Targeting Of Ovarian Cancer Cells Expressing Mucin Antigens – Prof Viness Pillay
Prof Viness Pillay
- Wits Medical School, Department of Pharmacy and Pharmacology, University of the Witwatersrand
Drug-Loaded Nanomicelles Conjugated To Mucin Antibodies For Direct Targeting Of Ovarian Cancer Cells Expressing Mucin Antigens.
Ovarian cancer (OC) is a challenging disease to treat and since it presents with few early symptoms, it is usually diagnosed late when in advanced stages. This study innovatively focuses on the combinatorial use of mucins such as MUC1, MUC4 and MUC16 for the design and development of a novel OC cell-targeting intraperitoneal drug delivery system to drastically improve the current chemotherapy of OC. The proposed mechanism of innovation is by employing antibody-conjugated nanomicelles to target mucin antigens expressed on OC cells. To our knowledge this has not been explored before. Ovarian tumors exhibit diverse and altered cell surface antigens such as, HE4, CA72-4, EGFR, SMRP and mucin (MUC16) that discriminate them from normal ovary cells and other normal cells lining the peritoneum. MUC16 is a known cell surface antigen in OC and since it is shed into the serum, it is widely used for diagnosing and managing epithelial OC. Mucins are synthesized in epithelial cells within the human body and protect epithelial cells from infection and injury by maintaining their hydrated and lubricated surfaces. During malignant transformation, the glycosylation of the mucin peptide backbone is altered, resulting in novel carbohydrate epitopes or the exposure of the peptide backbone. This change in mucin expression results in the loss of polarity of the epithelial cells and the subsequent increase in synthesis results in large quantities of mucin being either shed or secreted by tumor cells for metastasis and adhesion forming secondary tumor nodules. MUC16, a serum marker for OC, has been shown to facilitate the immune escape of OC cells. The non-specific distribution of chemotherapeutic drugs to tissues other than the tumor is one of the major undesirable side-effects of chemotherapy and this study therefore attempts to overcome this limitation by using MUC16 antibody-conjugated antineoplastic drug-loaded nanomicelles to target OC cells.
This research relates to the CANSA defined sphere of “Early diagnosis of Cancer” and “Prevention of Cancer”. It also touches on population health geared towards providing a new medical product that will ultimately lead to actual and measurable improvements in the treatment of ovarian cancer of the population which is currently sub-optimally treated and exacerbates the burden of disease.
Merging the research areas of Gynecological Oncology, Nanotechnology and Pharmaceutical Sciences for the design of the antibody-conjugated antineoplastic drug-loaded nanomicelles to target ovarian cancer cells constitutes the following specialist area of research:
- Oncology (treatment of ovarian cancer to ensure optimal health)
- Pharmaceutics (design of a biodegradable nano-enabled device as an intraperitoneal implant for site-specific delivery of antineoplastic drugs in treating ovarian cancer
Patients diagnosed with Ovarian Cancer (OC) are usually at an advanced stage (stage III or IV) when peritoneal spread has occurred. They have to undergo aggressive cyto-reductive surgery, chemotherapy and/or external beam radiotherapy. Paclitaxel (Abraxane®), doxorubicin (Doxil®) and carboplatin are standard chemotherapeutic drugs used for the treatment of OC. However, their use is limited by numerous debilitating side-effects, poor bioavailability and chemo-resistance. Several strategies have been explored for improving the bioavailability of these drugs with the use of nanotechnology. Polymeric nanomicelles of 20-100nm are able to increase the bioavailability of chemotherapeutic drugs to the tumor site. However, they do not provide superior cancer-cell targeting capability and there is no effective curative therapy. The use of intraperitoneal chemotherapy to improve treatment in post-operative OC patients has yielded controversial clinical outcomes that discourage its use as a treatment option compared to IV chemotherapy. However, the National Cancer Institute has recently proposed to make intraperitoneal chemotherapy part of the standard treatment in OC (http://ctep cancer gov/highlights/ovarian html 2006). In contrast, several studies have demonstrated the benefits of using intraperitoneal administration over IV and the combination of the two rather than IV alone.
The work reported here proposes an implantable intraperitoneal drug delivery device to provide therapy in OC is based on the fact that OC is also largely confined to the peritoneal cavity and as OC cells spread within the peritoneal cavity, they form secondary nodules by seeding to mesothelium-lined structures. Therefore, in light of improving the efficacy of intraperitoneal chemotherapy, this project developed an intraperitoneal implant comprising antineoplastic drug-loaded antibody-bound nanomicelles for specific targeting of OC cells expressing mucin antigens. It is important to note that the surface epithelium of ovaries is the only region in the ovaries that expresses mucins and since most OC are of epithelial origin, mucins can be exploited as attractive targets for the delivery of chemotherapeutic drugs. The change in mucin expression during the transformation of normal ovarian surface epithelium to cancer is an important step towards disease progression. It has been shown that OC cells that express MUC16 have an additional advantage to escape immune surveillance. This advantage enables OC cells to interact and adhere to the visceral mesothelium lining the peritoneum and organs found in the abdomen so that secondary tumor sites can be successfully established.
In this project we used the changes in mucin expression (specifically MUC16) in the malignant transformation of OC cells to enhance intraperitoneal chemotherapy via an implantable drug delivery device. The antibodyconjugated nanomicelles were encapsulated in a temperature and pH (peritoneal fluid pH ~ 7) sensitive hydrogel which was implanted via intraperitoneal injection. Once injected, the stimuli-responsive hydrogel transitioned into a semi-solid gel-like platform for affecting the release of the functionalized ‘smart’ nanomicelles. Following the release of the long-circulating antibody-bound nanomicelles (<100nm) in the peritoneal fluid, these targeted MUC16 antigen that is significantly over-expressed on OC cells at the primary tumor site (Stage I and II), those circulating in the peritoneal fluid and lastly, cancer cells forming nodules at distant sites in the peritoneal cavity (stage III and stage IV). The anti-mucin antibody-conjugated nanomicelles were internalized through endocytosis by tumor cells and thereby facilitated intracellular delivery of chemotherapeutic drugs, thus maintaining sustained and enhanced drug exposure to ovarian tumor cells. The nanomicelles are optimal for deeper penetration into tumor nodules considering that the pore size of most peripheral human tumors is approximately 200-600nm. This targeting system will help reduce the tumor load responsible for adhesion at the sites of secondary metastasis (peritoneal and abdominal surfaces). Several studies that are in advanced stages of development and in various phases of clinical trials also attempt to provide monoclonal antibody-mediated chemotherapeutics by utilizing various conjugates and antibodies linked directly to drug molecules. However, none of these strategies utilize the concept of linking antibodies to nanomicelles. We strategically chose to attach the anti-MUC16 antibody to a nanomicelle structure due to its potential pharmaceutical stability of the resultant targeting complex and also the fact that anti-MUC16 is extensively used in OC as a biomarker. Thus, with our technology we would merge the concepts of pharmaceutical nanotechnology and mucin biomarkers for the design of an effective strategy to treat OC via the intraperitoneal route.
- Design and Characterization of Endostatin-Loaded Nanoparticles for In Vitro Antiangiogenesis in Squamous Cell Carcinoma. Adeyemi, SA; Pillay, V. et al. Journal of Nanomaterials 2017.