title: Boosting Anti-Cancer Immunity with a Novel Chimeric Molecule
Creators: name: Gajurel, Damodar
Publisher: name: Griffith University
Year: 2017
Subjects: subject: Chimeric molecule
subject: Cancer therapies

description: High mortality, second only to cardiovascular causes, and high morbidity (physical as well as psychological) from cancer are unacceptable. Despite many years of multi-modality (conventional) treatment with surgery, radiotherapy, and chemotherapy, the status of cancer management, especially lung cancer, is still not satisfactory and alternate management strategies need to be developed. Anti-tumour immunotherapy is being explored as a potential new form of cancer therapies. Cancer vaccines, as forms of immunotherapy, have been developed and tested in clinical trials. Unfortunately, almost all of them did not achieve expected clinical responses. One of the reasons for this failure has been attributed to the poor immunogenicity/antigenicity of those vaccines. It has been suggested that whole tumour cells, harbouring all known and unknown cancer antigens, would better serve as vaccine antigens by circumventing the probability of tumour antigen loss due to tumour immune editing than selected single antigens used in most of those failed trials. The fact that even histologically similar types of tumours can harbour divergent antigens in different patients also explains the failure of clinical trials using allogeneic cancer cell vaccines suggesting that personalized tumour vaccines using autologous whole tumour cells would most likely ensure clinical success of cancer vaccines. But, at the same time, studies have shown that, in contrast to isolated single antigens, whole cancer cells also contain self-antigens that could lead, if not to outright immune tolerance, then to poor immune response, necessitating the use of immune-potentiating adjuvants to garner sufficient anti-tumour immune stimulation, i.e. enhanced immunogenicity. Therefore, combining autologous whole cancer cells with the appropriate immune-potentiating adjuvant in various novel ways could ensure a highly immunogenic and clinically effective vaccine. Considering the above facts, this study has been initiated to design a lung cancer vaccine with improved immunogenicity by conjugating a known strong and safe immune-potentiating adjuvant, i.e. unmethylated cytosine-phosphate-guanine oligodeoxynucleotide (CpG ODN) to whole A549 human lung cancer cell (as vaccine antigens) with the help of cross-linker bis-sulfosuccinimidyl suberate (BS3) in a novel way. Studies have shown that bi-directionally active NHS-ester moiety of BS3 covalently attach to the surface of the cancer cell membrane on one side and to one end of CpG ODN on the other side forming a novel chimeric molecule with 100-fold enhanced immune-potentiating capacity compared to their use in physical and temporal isolation. The formation of this covalently stable chimeric molecule using A549 whole lung cancer cells with CpG ODN, for the first time, was confirmed using fluorescein molecule tagged CpG ODNs and a scanning laser confocal microscope. The immunogenicity of this novel chimeric molecule was tested in vitro by measuring the level of the cytokines interleukin 6 (IL-6) and tumour necrosis factor alpha (TNF-α) released after exposure to U937 differentiated macrophages. The results of the level of the cytokines confirm that quantitatively more IL-6 and TNF-α, as surrogate markers for anti-cancer immune response, were released with the incorporation of the novel chimeric molecule than its control. The chimeric molecule induced the release of about 4500 pg/ml of TNF-α. This was very close to the amount of TNF-α (about 5000 pg/ml) released by 100 ng/ml of lipopolysaccharide (LPS) used as positive control. The negative control i.e. unconjugated CpG ODN and macrophages, released only around 500-600 pg/ml of TNF-α (i.e. our novel chimeric molecule induced nine times more cytokine release than its control. The difference in means of the cytokines released by them was also statistically significant (p &lt; 0.05). The results indicated that this novel chimeric molecule is highly immunogenic and could be further tested in animal models as the next step towards the development of a personalized anti-lung clinical cancer vaccine.