Anti-IFNG monoclonal antibody, clone YNH2.3 [PE/Cy7®]

Background Immune checkpoint inhibition and in particular anti-PD-1 immunotherapy have revolutionized the treatment of advanced melanoma. In this regard, higher tumoral PD-L1 protein (gene name: CD274) expression is associated with better clinical response and increased survival to anti-PD-1 therapy. Moreover, there is increasing evidence that tumor suppressor proteins are involved in immune regulation and are capable of modulating the expression of immune checkpoint proteins. Here, we determined the role of p53 protein (gene name: TP53) in the regulation of PD-L1 expression in melanoma. Methods We analyzed publicly available mRNA and protein expression data from the cancer genome/proteome atlas and performed immunohistochemistry on tumors with known TP53 status. Constitutive and IFN-gamma-induced PD-L1 expression upon p53 knockdown in wildtype, TP53-mutated or JAK2-overexpressing melanoma cells or in cells, in which p53 was rendered transcriptionally inactive by CRISPR/Cas9, was determined by immunoblot or flow cytometry. Similarly, PD-L1 expression was investigated after overexpression of a transcriptionally-impaired p53 (L22Q, W23S) in TP53-wt or a TP53-knockout melanoma cell line. Immunoblot was applied to analyze the IFN-gamma signaling pathway. Results For TP53-mutated tumors, an increased CD274 mRNA expression and a higher frequency of PD-L1 positivity was observed. Interestingly, positive correlations of IFNG mRNA and PD-L1 protein in both TP53-wt and -mutated samples and of p53 and PD-L1 protein suggest a non-transcriptional mode of action of p53. Indeed, cell line experiments revealed a diminished IFN-gamma-induced PD-L1 expression upon p53 knockdown in both wildtype and TP53-mutated melanoma cells, which was not the case when p53 wildtype protein was rendered transcriptionally inactive or by ectopic expression of p53(L22Q,W23S), a transcriptionally-impaired variant, in TP53-wt cells. Accordingly, expression of p53(L22Q,W23S) in a TP53-knockout melanoma cell line boosted IFN-gamma-induced PD-L1 expression. The impaired PD-L1-inducibility after p53 knockdown was associated with a reduced JAK2 expression in the cells and was almost abrogated by JAK2 overexpression. Conclusions While having only a small impact on basal PD-L1 expression, both wildtype and mutated p53 play an important positive role for IFN-gamma-induced PD-L1 expression in melanoma cells by supporting JAK2 expression. Future studies should address, whether p53 expression levels might influence response to anti-PD-1 immunotherapy.

Long noncoding RNA (lncRNA) are a class of endogenous, non-protein coding RNAs that are increasingly being associated with various cellular functions and diseases. Yet, despite their ubiquity and abundance, only a minute fraction of these molecules has an assigned function. LncRNAs show tissue-, cell-, and developmental stage-specific expression, and are differentially expressed under physiological or pathological conditions. The role of lncRNAs in the lineage commitment of immune cells and shaping immune responses is becoming evident. Myeloid cells and lymphoid cells are two major classes of immune systems that work in concert to initiate and amplify innate and adaptive immunity in vertebrates. In this review, we provide mechanistic roles of lncRNA through which these noncoding RNAs can directly participate in the differentiation, polarization, and activation of myeloid (monocyte, macrophage, and dendritic cells) and lymphoid cells (T cells, B cells, and NK cells). While our knowledge on the role of lncRNA in immune cell differentiation and function has improved in the past decade, further studies are required to unravel the biological role of lncRNAs and identify novel mechanisms of lncRNA functions in immune cells. Harnessing the regulatory potential of lncRNAs can provide novel diagnostic and therapeutic targets in treating immune cell related diseases.