Cancer is caused by a variety of defects that occur in genes that encode proteins and nucleotides to disrupt the machinery involved in cell growth. It is the progressive growth of tumors, along with anaplasia (loss of structural definition of cells), invasiveness, and metastasis, which characterize malignant diseases. Various approaches are used to eliminate or control cancer, including surgical excision of solid tumors, radiation therapy, chemotherapy, monoclonal antibody therapy, and more recently cell-based therapeutic vaccines. Each approach seeks to reduce or eliminate the burden of disease. Prevention of disease progression is the minimum desirable outcome and inhibition of tumor recurrence is the ultimate goal. Success with current therapies is highly variable from patient to patient and with a ‘cure for cancer’ still an undiscovered holy grail, novel treatment paradigms are needed to further the quest.
A rapidly growing field of cancer research is immunotherapy – harnessing of the body’s own immune system to seek out and kill cancer cells. Immunotherapies will likely become the treatment backbone in up to 60% of cancers over the next 10 years, compared to less than 3% today, with a market potential of around US$35 billion per annum.
The problem with cancer cells is that they cloak themselves in a manner that prevents their recognition by the immune system. Therapeutic cancer vaccines are a type of immunotherapy that involve programming the patient’s own immune cells firstly to recognize and destroy tumor cells and secondly to control tumor relapse by inducing immunological memory.
A further problem with mounting an immunological response is that cancer cells within primary tumors and metastatic tumors rapidly mutate, and the new genetic and protein markers (neoantigens) further elude immune surveillance. Importantly, exosomes have the full neoantigen repertoire of their malignant origin. Other strategies to capture the neoantigens from cancer patients rely on tissue biopsies to create therapies. These biopsies represent only a small snapshot of the cancer, are difficult (and sometimes impossible) to obtain, and the use of biopsies to generate personalized immunotherapies relies on expensive and time-consuming gene sequencing, neoepitope construct production, and imperfect algorithms to select what is relevant. Exosomes, by contrast, contain all the protein and genetic neoantigen fingerprints from primary and metastatic tumors in a package that may stimulate a more broad immune response than biopsy material.