Carcinoma gástrico com estroma linfoide: potencial biomarcador para imunoterapia “contra” o cancro do estômago?

O carcinoma gástrico é uma doença heterogénea do ponto de vista morfológico e molecular. Entre as variantes morfológicas, o carcinoma gástrico com estroma linfoide caracteriza-se pela abundância do infiltrado inflamatório rico em linfócitos no microambiente tumoral.

Através da investigação histopatológica, da análise digital e bioinformática (da expressão de proteínas e genes associados à resposta imunológica), os autores identificaram as características do carcinoma gástrico com estroma linfoide que são potencialmente relevantes para a aplicação de terapêuticas dirigidas contra as moléculas do checkpoint imunológico PD-1/PD-L1 (“imunoterapias”): associação com infecção por virus de Epstein-Barr e instabilidade de microsatellites, que definem dois subtipos moleculares de carcinoma gástrico com melhor resposta ao Pembrolizumab (anticorpo contra PD-1); imuno-expressão frequente (em 92% dos casos) de PD-L1, o biomarcador utilizado para seleccionar os doentes para imunoterapia; abundante infiltrado inflamatório intra- e peritumoral; enriquecimento de vias moleculares associadas à resposta T citotóxica e ativação de checkpoints imunológicos. Os resultados permitiram atribuir à infecção por virus de Epstein-Barr um papel determinante na constituição e promoção de um microambiente tumoral ativo do ponto de vista imunológico, com potencial aplicação terapêutica.

Autores e afiliações:

Irene Gullo^1,2,3,4, Patrícia Oliveira^3,4, Maria Athelogou⁵, Gilza Gonçalves^2,3,4,6, Marta L Pinto^4,7,8, Joana Carvalho^3,4, Ana Valente^3,4, Hugo Pinheiro^3,4,9, Sara Andrade^3,4,10, Gabriela M. Almeida^3,4, Ralf Huss⁵, Kakoli Das¹¹, Patrick Tan^11,12,13, José C. Machado^2,3,4, Carla Oliveira^2,3,4, Fátima Carneiro^1,2,3,4

¹Department of Pathology, Centro Hospitalar de São João, Al. Prof. Hernâni Monteiro, 4200-319 Porto, Portugal

²Department of Pathology, Faculty of Medicine of the University of Porto (FMUP), Al. Prof. Hernâni Monteiro, 4200-319 Porto, Portugal

³Institute of Molecular Pathology and Immunology at the University of Porto (Ipatimup), Rua Júlio Amaral de Carvalho 45, 4200-135 Porto, Portugal

⁴Instituto de Investigação e Inovação em Saúde (i3S), University of Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal

⁵Definiens AG, Bernhard-Wicki Str 5, 80636 Munich, Germany

⁶Department of Biomedical Sciences and Medicine, University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal

⁷INEB-Institute of Biomedical Engineering, University of Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal

⁸ICBAS-Institute of Biomedical Sciences Abel Salazar, University of Porto, Rua Jorge de Viterbo Ferreira 228, 4050-343 Porto, Portugal

⁹Hospital Senhora da Oliveira, Rua dos Cutileiros 114, 4835-044 Guimarães, Portugal

¹⁰ Department of Biomedicine, Faculty of Medicine of the University of Porto (FMUP), Al. Prof. Hernâni Monteiro, 4200-319 Porto, Portugal

¹¹ Cancer and Stem Cell Biology Program, Duke-NUS Medical School, 8 College Road, 169857, Singapore

¹² Genome Institute of Singapore, Biopolis, 60 Biopolis St, 138672, Singapore

¹³ Cancer Science Institute of Singapore, National University of Singapore, 14 Medical Dr, 117599, Singapore

Abstract:

Background: Gastric cancer with lymphoid stroma (GCLS) is characterized by prominent stromal infiltration of T-lymphocytes. The aim of this study was to investigate GCLS biology through analysis of clinicopathological features, EBV infection, microsatellite instability (MSI), immune gene-expression profiling and PD-L1 status in neoplastic cells and tumor immune microenvironment.

Methods: Twenty-four GCLSs were analyzed by RNA in situ hybridization for EBV (EBER), PCR/fragment analysis for MSI, immunohistochemistry (PD-L1, cytokeratin, CD3, CD8), co-immunofluorescence (CK/PD-L1, CD68/PD-L1), NanoString gene-expression assay for immune related genes and PD-L1 copy number alterations. CD3+ and CD8+ T-cell densities were calculated by digital analysis. Fifty-four non-GCLSs were used as control group.

Results: GCLSs displayed distinctive clinicopathological features, such as lower pTNM stage (p = 0.02) and better overall survival (p = 0.01). EBV+ or MSI-high phenotype was found in 66.7 and 16.7% cases, respectively. GCLSs harbored a cytotoxic T-cell-inflamed profile, particularly at the invasive front of tumors (p < 0.01) and in EBV+ cases (p = 0.01). EBV+ GCLSs, when compared to EBV− GCLSs, showed higher mRNA expression of genes related to Th1/cytotoxic and immunosuppressive biomarkers. PD-L1 protein expression, observed in neoplastic and immune stromal cells (33.3 and 91.7%, respectively), and PD-L1 amplification (18.8%) were restricted to EBV+/MSI-high tumors and correlated with high values of PD-L1 mRNA expression.

Conclusions: This study shows that GCLS has a distinctive clinico-pathological and molecular profile. Furthermore, through an in-depth study of tumor immune microenvironment—by digital analysis and mRNA expression profiling—it highlights the role of EBV infection in promoting an inflamed tumor microenvironment, with putative therapeutic implications.

Revista: Gastric Cancer, 2018

Link: https://link.springer.com/article/10.1007/s10120-018-0836-8