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M. Janakiram

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    OA 13 - Immuno-Biology (ID 677)

    • Event: WCLC 2017
    • Type: Oral
    • Track: Immunology and Immunotherapy
    • Presentations: 1
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      OA 13.03 - Wide Expression of Alternative Immune Checkpoint Molecules, B7x and HHLA2, in PD-L1 Negative Human Lung Cancers (ID 10020)

      11:00 - 12:30  |  Author(s): M. Janakiram

      • Abstract
      • Slides

      Immunotherapy targeting the PD-1/PD-L1 pathway has dramatically changed the treatment landscape of non-small-cell lung carcinoma (NSCLC). We previously demonstrated that HHLA2, a recently identified B7 family immune inhibitory molecule, was widely expressed in NSCLC. To better understand the immune evasion mechanisms within the tumor microenvironment, we compared the expression profiles and functional roles of PD-L1 with potential alternative immune checkpoints, B7x and HHLA2.

      Expression was assessed by immunohistochemistry using tissue microarrays consisting of 392 NSCLC tumor tissues (mostly resected stage I to III), including 195 tumors in the discovery (D) set and 197 cases in the validation (V) set. Positive PD-L1 cases were defined as samples with percentage of tumor cells revealing membranous staining of PD-L1 ≥ 1% with SP142 antibody. Human T cells were purified from eleven donors. Control human IgG, human PD-L1-Ig, human B7x-Ig and human HHLA2-Ig were used to determine the effects of PD-L1, B7x and HHLA2 on T cell proliferation and cytokine production [Human Th Cytokine Panel: IL-5, IL-13, IL-2, IL-6, IL-9, IL-10, IFN-γ, TNF-α, IL-17F, IL-17A, IL-4, IL-21 and IL-22].

      PD-L1 expression was detected in 25% and 31% of tumors in the D and V sets respectively, and was associated with higher stage and lymph node involvement in both cohorts. Multivariate analysis further showed that stage, TIL status and lymph node involvement were independently associated with PD-L1 expression. B7x was expressed in 69% and 68% of cases, while HHLA2 was positive in 61% and 64% of tumors in the two sets. Triple positive expression was detected in 13% whereas triple negative in 15% of cases. The double-expression of PD-L1 with B7x or HHLA2 was rare, 6% and 3% respectively. Interestingly, the majority (78%) of PD-L1 negative cases expressed B7x, HHLA2 or both. Moreover, the triple positive group correlated with more TIL infiltration as compared to the triple negative group (P = 0.0175). At the same concentration, B7x-Ig and HHLA2-Ig inhibited TCR-mediated proliferation of both CD4 and CD8 T cells significantly more robustly than PD-L1-Ig. All three significantly suppressed a variety of cytokine production by T cells.

      The majority of PD-L1 negative lung cancer cases express alternative immune checkpoint molecules (B7x, HHLA2 or both). The potential role of the B7x/HHLA2 pathway in mediating immune evasion in PDL1 negative tumors deserves to be explored to provide the rationale for an effective immunotherapy strategy in these tumors.

