(O20) Gene Expression Profiles Associated with Early Relapse in Canine Multicentric High-grade B-cell Lymphoma

Abstract: Background
Multicentric high-grade B-cell lymphoma (mhBCL) is the most common subtype of canine lymphoma. Although chemotherapy by CHOP protocol induces remission in most cases, part of the cases develops early relapse during the first remission induction chemotherapy.

Objective
To investigate the gene expression profiles associated with early relapse during the first remission induction chemotherapy in canine mhBCL.

Animals
Twenty-five mhBCL cases diagnosed with centroblastic type and treated by UW-25 protocol as first remission induction chemotherapy were included in this study. Sixteen cases completed UW-25 protocol without relapse (S-group), and nine relapsed during the protocol (R-group) (Figure 1).

Methods
Tumor cell samples were collected by fine-needle aspirations at diagnosis, and RNA was extracted from the samples. RNA-seq was performed using the samples of eighteen dogs and the gene expression profiles were compared between the S and R-groups. The mRNA expression levels of the extracted differentially expressed genes (DEGs) were compared between the S and R-groups using the samples of twenty-three dogs by RT-qPCR (Figure 1).

Results
Extracted 179 DEGs included the genes related to T cell receptor signaling pathway and PD-L1 expression and PD-1 checkpoint pathway. CD3E, ITK, and LAT genes were confirmed to be significantly upregulated in the R-group by RT-qPCR (Figure 2).

Conclusions and clinical importance
The results of this study suggested that the tumor microenvironment including T-cells in mhBCL tissues were associated with the early relapse during first UW-25 protocol.