MICA: Immunotherapy for oral cancer prevention and treatment

Worldwide, oral cancer (OSCC) is the eighth most common cancer and a major global health concern, with an annual incidence of around 398,000 and more than 222,000 deaths worldwide. OSCC is often difficult to treat; surgery and radiotherapy remain the standard treatments but, despite improvements, are associated with significant morbidity and a relatively static 5-year survival rate of around 50-60%.

Around 15-80% of OSCC develop from a precursor lesion (OPL), most commonly a white patch (leukoplakia). The current gold standard for determining leukoplakia management is pathological diagnosis of dysplasia, with transformation rates of 24.1% being reported in severe dysplasia. At present, the only effective treatment is surgical excision. However, studies indicate that this is not likely to reduce the risk of recurrence or malignant change. It is clear that more effective treatments are required for both premalignant lesions and established OSCC.

Immunotherapy represents the most promising new cancer therapy for several decades. These treatments harness the power of the patient's immune system to fight the cancer, in the same way that the immune system might fight a virus. Cancers are recognised by the immune system as "foreign' because they express proteins (antigens) not usually found in normal tissues. Some patients have a strong immune response against their cancer; this can be seen in the tumour tissue as immune cells (lymphocytes) attacking the cancer cells. However, most cancers are not well recognised by the immune system, and the immune system needs to be stimulated to respond. If we identify the abnormal proteins on the cancer cells, then we can design vaccines against these antigens to generate an immune response against the cancer cell (just like vaccinating against a virus); recent studies have shown that premalignant lesions in the cervix can be successfully cleared through vaccination. This type of cancer is caused by a virus (human papillomavirus) and vaccines are designed to target viral proteins. By contrast, in most cancers and premalignant lesions targetable antigens are unknown.

This proposal aims to identify common tumour associated antigens (TAA; cancer testis antigens and others) expressed in OPL and OSCC as part of a therapeutic strategy to develop vaccines to treat and prevent this disease. Expression of cancer testis antigens have been described in OPL, and preliminary work by the Cancer Research Malaysia (CRM) team have identified two antigens, MADGED4B and FJX1 that are commonly expressed in both OPL and OSCC. We will extend this analysis, examining global gene expression in cases of dysplasia and with OSCC to identify common tumour antigens, focusing on those found early in the disease process, before cancer develops. We will use these antigens to make vaccines using a novel vaccine design developed by the University of Southampton team (UoS), and test these in a humanised mouse cancer models. The vaccine is based on a plant virus that produces a powerful immune response in a similar way to human viruses; but is safe, cheap and readily mass-produced in plants. This is attractive for low-to-middle income economies such as Malaysia, where OSCC is especially prevalent, but conventional treatment is unattainable for many patients. A cost-effective vaccine strategy that can target OPL before cancer develops and also treat OSCC would transform the management of this disease worldwide.

Oral cancer (OSCC) is common worldwide with more 220,000 deaths annually. Studies report that ~15-80% of OSCCs develop from pre-existing, premalignant precursor lesions (OPL), most commonly a white patch (leukoplakia). The global prevalence of leukoplakia is estimated to be 2.6%, with reported rates of malignant transformation of 3.5%.

Immunotherapy is a highly promising new cancer therapy, with checkpoint inhibitors such as anti-PD1, predicated on boosting pre-existing anti-tumour immunity. Vaccines developed to generate immune responses against specific tumour antigens are also producing promising clinical results, notably in pre-malignant cervical dysplasia, suggesting a similar strategy could be used to target OPL.

This project aims to identify shared antigens overexpressed in OPL and OSCC using transcriptomic microarrays. OPL transcriptome data will be compared with RNA sequencing datasets of OSCC (UoS & TCGA) to identify common antigens expressed across the disease process. For example, MAGED4B and FJX1 have already been shown by the CRM team to be overexpressed in both OPL and OSCC. The common antigens will be taken forward for vaccine construction using a novel plant viral particle platform developed by the UoS team. This safe single-strand RNA containing vaccine acts through engagement of TLR7/8 to activate immune mechanisms closely resembling those of a pathogenic viral infection, inducing a cytotoxic CD8 T-cell response of high magnitude and durability as well as tumour-specific CD4 T-cells. Vaccines will be tested in the HLA-A2 humanized mouse model (B6.Cg-Tg(HLA-A/H2-D)2Enge/J) using murine tumour cell lines (B16/F10 melanoma and 4NQO-derived oral cancer lines) expressing human HLA-A2 and transfected with selected target antigens).This study will establish proof-of principle of new prophylactic vaccines, which can be produced at low cost, to manage patients with OPL, and inform design of future immunotherapy trials for OSCC prevention.

Oral squamous cell carcinoma (OSCC) is the eighth most common cancer worldwide, with a annualincidence of 398,000 and over 220,000 deaths, yet it remains an understudied tumour type. This has impacted on clinical outcome, with 5-year patient survival rates remaining relatively static at 50-60% for the past several decades. Management of patients is often by a costly multidisciplinary approach involving surgery and/or radiotherapy followed by reconstruction and rehabilitation. Treatment results in considerable physical and psychological morbidity and may not prolong life for many of the patients. Early detection of cancer affords a better chance for patient survival. Many cancers including OSCC are preceded by an oral premalignant lesion (OPL) which permits for early detection and intervention. At present, the only available treatment is surgical excision that comes often with functional and aesthetic consequences of resection. While surgery may have a short-term beneficial effect, observational studies indicate that this is not likely to reduce the risk of later recurrence (in up to 35% of patients) nor malignant transformation at another or even at the same site. It is clear that more effective treatments are required for both premalignant lesions and established OSCC.

Immunotherapy is rapidly gaining its place as a mainstream treatment of solid cancers; antibodies targeting the immune checkpoint inhibitor PD1, show efficacy in around 25% of OSCC patients. However, this is a costly treatment, and most patients do not benefit. While there is intriguing potential for the development of patient-specific vaccines based on an individual's tumour mutanome, the costliness and technical difficulty of such an approach means that, even if successful, it is unlikely to benefit most patients. Identifying common tumour antigens that are shared between patients, expressed in the premalignant phase of disease and expressed in different cancer types could lead to the production of generic cancer vaccines that would be provide a cheap and widely available treatment for OPL and OSCC. This project aims to identify common OPL and OSCC antigens, including novel tumour antigens already identified by the Cancer Research Malaysia team, and construct plant virus-based vaccines, using technologies developed by the University of Southampton team for preclinical testing. These vaccines are cost-effective, can be readily mass-produced in plants, and are ideally suited for healthcare delivery in low and middle income countries (LMICs).

The data from the proposed programme will establish proof-of-principle for a new, cost-effective prophylactic vaccine concept to manage a large and economically important group of patients worldwide. These data will be used to inform design of the next group of randomized immunotherapy trials on patients with oral pre-malignancy where no successful intervention is currently available. The development of immunotherapies that can successfully prevent the cancer transformation will have significant economic impact and quality-adjusted life year (QALY) cost-benefit. Most importantly, if cancer is preventable, life expectancy of general public will be extended.