Increasing the Expression of Programmed Death Ligand 2 (Pd-L2) But Not 4-1Bb Ligand in Colorectal Cancer Cells Publisher Pubmed



Shakerin P^{1, 2} ; Sedighi Moghadam B² ; Baghaei K¹ ; Safaei Naraghi Z³ ; Kamyab Hesari K³ ; Asadzadeh Aghdaei H¹ ; Shokouhi Shoormasti R⁴ ; Fazeli MS⁵ ; Nourizadeh M⁴
Source: Molecular Biology Reports Published:2020

Abstract

Immune checkpoint (ICP) molecules modulate the immune response by either inducing or preventing T cell activation. Over-expression of some ICPs on malignant cells has been shown to regulate anti-tumor immune responses. We aimed to investigate the expression levels of two immune checkpoint molecules which have not been studied extensively in patients with colorectal cancer (CRC). Programmed Death Ligand 2 (co-inhibitory) and 4-1BB ligand (co-stimulatory) were assessed in tumor tissues of CRC patients compared to the adjacent normal tissues. Following tissue excision during surgical operation from 21 CRC patients, RNA extraction, cDNA synthesis and semi-quantitative real-time PCR were done for measuring the expressions of PD-L2 and 4-1BBL genes. In protein level, indirect immunohistochemistery (IHC) was performed on tissue sections. We revealed that PD-L2 was expressed in about 81% CRCs and insignificantly correlated with the tumor differentiation grade. Although a 3.25-fold change in the gene expression of PD-L2 was found in tumor tissues compared to the adjacent normal tissues (P = 0.005), but decreased level of 4-1BBL in counterpart tissues was not significant. Our results were confirmed by IHC for PDL-2 (P = 0.02) and 4-1BBL, however it was not statistically significant for the latter one. Although not significant, we could find an association between the elevated expression of PD-L2 and the tumor differentiation grade. Increased expression of negative regulator of the anti-tumor immune responses like PD-L2, as a prominent way of tumor escape, can be considered for cancer immunotherapy approaches in CRC patients using blocking monoclonal antibodies. © 2020, Springer Nature B.V.