Immune checkpoints in oral carcinogenesis

Head and neck squamous cell carcinoma (HNSCC) is a common and aggressive malignancy. It includes the tumors arising in the head and neck area with oral cancer representing one of the most common types. Intraorally, squamous cell carcinomas arising from the tongue (OTSCC) are the most frequent. The multimodality treatment regime includes surgery, radio and/or chemotherapy depending on the spread of the disease. Unfortunately, the five-year survival rates in the Nordic countries remain between 50-60% for oral cancer, with the incidence of OTSCC increasing without clear etiology. The newest addition to the treatment regime of recurrent and/or metastasized oral squamous cell carcinoma (OSCC) patients is immune checkpoint inhibitors (ICIs), namely anti-PD-1. These ICIs provide improved survival rates, and the expression of the immune checkpoints (ICs) are being investigated as potential prognostic factors. This dissertation aimed to investigate the role of ICs in the development of oral carcinogenesis. Our first project was to explore the expression of selected ICs, indoleamine 2,3-dioxygenase 1 (IDO1), and programmed death-ligand 1 (PD-L1) in oral dysplasia, a potentially malignant oral lesion. We retrospectively gathered 63 archival oral dysplasia samples from Oulu and Tampere University Hospitals from 2005 to 2016, with 9 samples extracted during wisdom tooth extractions to act as healthy controls. The samples were stained for anti-PD-L1 and anti-IDO1 and scored for the expression of both immune checkpoints, dysplastic grade, and immune cell infiltration. The expression of the ICs was modulated during the development of dysplastic changes associated with inflammatory cell infiltration. Eight patients were followed up to 36 months and biopsies were taken more than once. The expression of ICs fluctuated over time, suggesting that they are not useful as biomarkers for malignant transformation. Since the start of our first project, several articles have been published on the prognostic value of ICs in OSCC. Our second project aimed to systematically review the prognostic value of ICs in OSCC. By the end of 2017, 12 ICs had been studied for their prognostic value in OSCC. Seven of them (ALHD1, FKBP51, PD-L1, B7-H3, B7-H4, B7-H6, and IDO1) had been reported as adverse prognostic factors and five (CTLA-4, PD-1, PD-L2, TLT-2 and VISTA) did not have prognostic value. Only two molecules, PD-L1 and B7-H3, had sufficient data for conducting a meta-analysis. PD-L1 had controversial findings as a prognostic marker, with weak evidence suggesting high B7-H3 expression was an adverse prognostic factor for overall survival. Based on the systematic review results, we aimed to validate B7-H3 as an adverse prognostic factor in OTSCC. 323 OTSCC samples from Brazil, Finland, and Norway were retrospectively gathered and stained for B7-H3. High B7-H3 expression was not significantly associated with patient survival in the whole OTSCC cohort. The immune status/phenotype of the Brazilian and Finnish cases (n=191) was analyzed by the amount of tumor infiltrated lymphocytes (TILs), classifying the cases into ‘immune hot’ and ‘immune cold’. The immune status of the patient (n=191) was significantly associated with patient survival, with immune cold patients having an adverse outcome in univariate and multivariate survival. Our findings suggest that the immune status of the tumor should be considered when investigating the prognostic value of ICs and could be an individual prognostic factor aiding in identifying potential high-risk cases. Based on studies I and II, a research question arose regarding what would be the functional effect of the ICI on lymphocyte infiltration in the presence of cancer cells and what would happen to the cross-talk between lymphocytes and cancer cells. In a newly developed microfluidic chip model, we injected OTSCC cells (HSC-3) embedded in a 3D human tumor-derived matrix “myogel/fibrin” together with different lymphocyte populations (CD4+ T, NK and CD8+ T cells). The chips were incubated with different ICIs, anti-PD-1, nivolumab or the IDO1 inhibitor, epacadostat. Study IV revealed that each subpopulation of lymphocytes responded differently to ICI therapy with the release of specific cytokines. The IDO1 inhibitor significantly increased the migration of CD4+ T and NK cells towards the OTSCC cell line. This could potentially reverse the immune cell exclusion firing up cold tumors to hot. Anti-PD-1 significantly increased the release of IL-6, IL-8, and MIP-1α from CD4+ T, NK and CD8+ T cells, respectively. The elevation of IL-6 and IL-8 serum levels after ICI therapy in patients has been associated with nonresponding tumors. The blockage of these cytokines may be a promising direction for future studies.

Grantor dc:publisher

Helsingin yliopisto

Year dc:date.issued

2022

Author dc:creator

• Sieviläinen, Meri

• suupatologia

Statement dc:rights

• Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.
• This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
• Publikationen är skyddad av upphovsrätten. Den får läsas och skrivas ut för personligt bruk. Användning i kommersiellt syfte är förbjuden.

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/10138/350042

OAI record oai:identifier

https://helda.helsinki.fi/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Ahelda.helsinki.fi%3A10138%2F350042