Abstract 5070: Chemokine expression signatures in infiltrated vs non-infiltrated tumors
Authors: Pabla Sarabjot , Conroy Jeffrey , Nesline Mary , Glenn Sean , Burgher Blake , Qin Maochun , Andreas Jonathan , Giamo Vincent , Lenzo Felicia L. , Omilian Angela , Bshara Wiam , Papanicolau-Sengos Antonios , Wang Yirong , Ernstoff Marc , Gardner Mark , Morrison Carl 
Published: August 2018

Background: Previous studies in animal models have shown that expression of specific chemokines determines immune cell infiltration in the tumor microenvironment. More specifically, low expression of CXCL9/10/11, CXCR3, and CCL5, coupled with high expression of CCL2, CCR2, CCR4, CCR5, CCL22, CXCL12, and CXCR4, leads to an exclusion of effector T-cells in the tumor microenvironment while allowing the entry of Treg and MDSC(s).

Methods: 300 formalin-fixed, paraffin-embedded (FFPE) metastatic cutaneous melanoma samples were evaluated by the RNA-seq component of a comprehensive immune profile panel to measure transcript levels of chemokine genes. Resultant data was QC filtered, normalized and ranked based on an assorted reference population of various tumor types. CD8 expression was used to categorize tumors as inflamed (CD8 Rank ≥ 75), borderline ≥ 25 CD8 Rank &lt; 75) and immune deserts (CD8 Rank &lt; 25). T-cell infiltration is defined by CD8 immunohistochemistry with following definitions: Noninfiltrated - Sparse number of CD8+ T-cells that infiltrate nests of neoplastic cells and represent less than 5% of the tumor. Infiltrated - Frequent CD8+ Tcells that infiltrate nests of neoplastic cells in an overlapping fashion at least focally and represent more than 50% of the tumor cells.

Results: CD8 infiltration by immunohistochemistry showed high correlation with CD8 gene expression by RNAseq with infiltrated tumors showing significantly higher expression of CD8 than non-infiltrated tumors (v.test:9.47, p= 2.79E-21; Wilcoxon rank sum test p&lt;0.05). Moreover, 73% of inflamed tumors were categorized as “infiltrated” by IHC while 93% of Immune desert tumors were categorized as “non-infiltrated” by IHC. Chemokine expression significantly correlated with infiltration status by IHC, wherein, CCL5, CCR5, CCL4, CXCR3, CXCL9, CCL2, CCL22, CCL3, and CXCL10 were significantly under expressed in tumors lacking infiltrating effector T-cells (Wilcoxon rank sum test p&lt;0.05, Tukey HSD adjusted p &lt;0.001). Overall ANOVA results showed significant relationship between gene expression of these chemokines and Infiltration status by CD8 IHC (p &lt;0.05).

Conclusion: In 300 metastatic cutaneous melanoma cases, we demonstrated that tumor inflammation status by CD8 expression by RNAseq correlated with CD8 infiltration pattern by IHC. Moreover, expression of Infiltrated and non-infiltrated tumors shows distinct chemokine signatures where higher CD8 T-cell infiltration correlates with higher expression of studied chemokines in the tumor microenvironment. It requires further investigation to better understand the interplay of chemokines and cytokines in the tumor microenvironments that drive the immune cycle in melanoma.

Citation Format: Sarabjot Pabla, Jeffrey Conroy, Mary Nesline, Sean Glenn, Blake Burgher, Maochun Qin, Jonathan Andreas, Vincent Giamo, Felicia L. Lenzo, Angela Omilian, Wiam Bshara, Antonios Papanicolau-Sengos, Yirong Wang, Marc Ernstoff, Mark Gardner, Carl Morrison. Chemokine expression signatures in infiltrated vs non-infiltrated tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5070.