T Cell Ig and ITIM Domains (TIGIT) Expression in Multiple Myeloma

Background

Neoplastic myeloma cells show a wide variety of mechanisms that induce the microenvironment, allowing immune evasion and promoting their proliferation, survival, migration and drug resistance. In this context, immunocheckpoints are particularly important, representing the modulators of signal pathways responsible for immune tolerance, a mechanism that prevents the destruction of cancer cells by the immune system. T cell Ig and ITIM domains (TIGIT), a member of the poliovirus (PVR) /nectin receptor family, is a new immune checkpoint that negatively regulates T cell functions. In Multiple Myeloma (MM), TIGIT could play a relevant role leading to immunological escape. TIGIT performs its task mainly through binding ligands: CD155 and CD112, through which it inhibits the cytotoxicity of CD8+ T cells, as well as that of NK. In This Study, we evaluate the presence of TIGIT in bone marrow using instant digital pathology.

AIMS

Aims of this study are to develop a valid and reproducible workflow for instant digital pathology, to demonstrate the presence of TIGIT-positive T lymphocytes in bone marrow of patients with MM and to evaluate its correlation with clinical features

PATIENTS and Methods

18 patients with newly diagnosed MM not previously treated, were evaluated in this study. The sample was enrolled from November 2022 to May 2023.

Bone marrow blood was loaded on a porous matrix able to retain cells (Cytomatrix, UCS Diagnostics srl, Rome) for real time assessment of sample adequacy, morphological details preservation, and composition of hematopoietic subpopulations, using an ex-vivo fluorescent confocal microscope (FCM). Expert pathologists compared the digital FCM images with permanent Formalin Fixed Paraffin Embedded (FFPE) sections of the matrix and trephine bone marrow biopsy. Immunohistochemistry for TIGIT (TG-1 Clone, OncoDianova) was performed on matrix FFPE sections.

RESULTS

Our results showed that 15/17 (88%) patients resulted positive for TIGIT and 2/17 (12%) were negative. TIGIT expression was found mainly on CD8+ T lymphocytes, TIGIT positivity was correlated with parameters that define the aggressiveness of myeloma disease such as PC > 60% or FLC > 100, ISS score, R-ISS score, cytogenetic risk and LDH > 220mU/ml.

Among the patients defined as “ultra-High Risk”, 9/10 (90%) resulted positive for TIGIT. Comparing TIGIT with the MM International Staging System (ISS), we observed that all patients with scores II and III were positive for TIGIT (100%) while 78% of them with ISS I results positive.

Conclusions

Our results suggest that FCM can be applied immediate evaluation of bone marrow aspirates, preserving the cellular sample for final histological analysis. “Furthermore, our data shows the positivity of TIGIT in 88% of patients, demonstrating the presence of this immune checkpoint in the bone marrow microenvironment.

These data will need to be confirmed in a larger group of patients, but they open up the possibility of new target treatments in multiple myeloma