Molecular Pharming for Cancer Vaccines and Treatment

Dear Colleagues,

Cancer is among the leading causes of mortality worldwide and the major causes of cancer-related deaths include colorectal, lung, breast and prostate cancer. Treatment of cancer has significantly improved over the last few decades with conventional strategies such as surgery, radiotherapy, chemotherapy that provide cancer patients with a significantly high survival rate. Notwithstanding, cancer has not yet been eradicated and effectual, long-term cancer treatment is still challenging due to tumor recurrence, metastasis and emergence of multi-drug resistance. Many cancer interventions such as immunotherapeutic drugs have been approved by the US FDA for cancer treatment. Anti-cancer vaccines could be prophylactic that precludes infections with viruses that cause cancer or could be therapeutic to treat already established cancers.

In recent times, plants are being increasingly used in the prophylaxis and treatment of cancer due to their high safety and lack of human pathogens, longer shelf-life, patient compliance with non-invasive oral administration, ability to stimulate the oral mucosa as the first line of immune defense and ability to be manufactured at a large scale and at low costs. Efforts to reduce the incidence of infection using plant-made vaccines to combat oncolytic viruses such as HPV, HBV and HCV are of great use in developing nations where this would make a big difference to the quality of life in millions impacted by these viruses. The production of vaccines and monoclonal antibodies in a manner that requires minimum processing or medical infrastructure strongly supports the consideration of plant-derived biologics as a means to enable these countries. Plants have been developed in various ways for production of anticancer biopharmaceuticals. Initially, vaccine antigens of interest were stably expressed using transgenic plants whose nuclei or chloroplast DNAs were transformed by the integration of the transgene. Subsequently, transient expression systems were designed using agrobacterium-based infiltration and by the use of plant viral expression vectors. Significantly, deconstructed viral vectors have been developed that enable ease of manipulation and are biocontainable as different parts of the viral genome are divided into modules that upon entry into plant cells can recombine into a fully functional replicon. There are both advantages and pitfalls to either approach and decisions on which platform to use are based on the nature and future use of the anti-cancer protein produced. Transgenic technology can be used in situations where the antigens can be easily stored as seed and subsequently scaled up based on need. In other instances, virus-like particles (VLPs) could be useful for rapidly generating vaccines against cancer-causing infectious viruses. Plants have also been used to produce subunit or full protein vaccines, monoclonal antibodies and plant virus nanoparticles against cancer. 

Nowadays, plants are routinely being used as effectual production platforms for the development of anti-cancer biologics leading to novel immunotherapeutics, anti-cancer vaccines and drug-delivery modalities. Several immunogens based on tumor-associated antigens and biosimilar / biobetter antibodies have been generated and optimized for expression in plants. Plant viral nanoparticles particularly those derived from tobacco mosaic virus or cowpea mosaic virus have shown great promise as immunotherapies triggering tumor-associated immune cells and as carriers of drugs delivering conjugated chemotherapeutics directly into the tumors.  Advancements have also been made in developing lectins that are capable of selective recognition of cancer cells. The level of simplicity at which plant systems can be applied for the production of the above products presents a viable opportunity to further generate inimitable and exciting anti-cancer biologics. 

Aim of the special issue

This special issue of ‘Vaccines’ invites original research articles and reviews concerning the current state of the art of plant-derived technologies to preclude or treat cancers. This issue addresses plant-based production systems that preclude solid tumors, lymphomas and infection by oncogenic viruses along with plant-based cancer immunotherapy (monoclonal antibodies) for use in developing countries.  Also addressed by this current issue are plant-derived pharmaceuticals that have been developed to fight cancer. The recent discovery of plant virus nanoparticles (VNPs) that target and penetrate solid tumors is particularly exciting. Plant viral nanoparticles can be produced in a facile manner with drugs functionalized to their surfaces, enabling them to easily home in and block tumor progression.

Dr. Srividhya Venkataraman
Prof. Dr. Kathleen Hefferon
Guest Editors

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• genetic engineering
• plant molecular pharming
• plant virus VLPs
• VNPs
• monoclonal antibodies
• anti-cancer vaccines
• immunotherapeutics
• drug delivery
• solid tumors