Differential Effects on the Translation of Immune-Related Alternatively Polyadenylated mRNAs in Melanoma and T Cells by eIF4A Inhibition

Abstract

Targeting the translation initiation complex eIF4F, which binds the 5′ cap of mRNAs, is a promising anti-cancer approach. Silvestrol, a small molecule inhibitor of eIF4A, the RNA helicase component of eIF4F, inhibits the translation of the mRNA encoding the signal transducer and activator of transcription 1 (STAT1) transcription factor, which, in turn, reduces the transcription of the gene encoding one of the major immune checkpoint proteins, i.e., programmed death ligand-1 (PD-L1) in melanoma cells. A large proportion of human genes produce multiple mRNAs differing in their 3′-ends through the use of alternative polyadenylation (APA) sites, which, when located in alternative last exons, can generate protein isoforms, as in the STAT1 gene. Here, we provide evidence that the STAT1α, but not STAT1β protein isoform generated by APA, is required for silvestrol-dependent inhibition of PD-L1 expression in interferon-γ-treated melanoma cells. Using polysome profiling in activated T cells we find that, beyond STAT1, eIF4A inhibition downregulates the translation of some important immune-related mRNAs, such as the ones encoding TIM-3, LAG-3, IDO1, CD27 or CD137, but with little effect on the ones for BTLA and ADAR-1 and no effect on the ones encoding CTLA-4, PD-1 and CD40-L. We next apply RT-qPCR and 3′-seq (RNA-seq focused on mRNA 3′ ends) on polysomal RNAs to analyze in a high throughput manner the effect of eIF4A inhibition on the translation of APA isoforms. We identify about 150 genes, including TIM-3, LAG-3, AHNAK and SEMA4D, for which silvestrol differentially inhibits the translation of APA isoforms in T cells. It is therefore crucial to consider 3′-end mRNA heterogeneity in the understanding of the anti-tumor activities of eIF4A inhibitors.

Comparing the Effects of Rocaglates on Energy Metabolism and Immune Modulation on Cells of the Human Immune System

“…Zotatifin reduced the expression of CD154 (CD40L), the interaction partner of CD40 expressed on antigen-presenting cells, whereas CR-31-B (−) and silvestrol did not affect CD154 expression. This is in line with the published data, as Biswas et al also found that silvestrol did not regulate CD154 at the mRNA level in activated T cells [ 32 ]. Moreover, the pharmacological inhibition of elF4A reduced cytokine release (IL10, IFNγ and IL17A).…”

Class IV semaphorins in disease pathogenesis

“…Sema4D is associated with the etiology of various types of cancer. 88,89 Roles for Sema4D have been demonstrated in breast cancer, [90][91][92][93][94][95][96][97][98][99][100][101] colorectal carcer, [102][103][104][105][106][107][108] gastric cancer, 109 esophageal cancer, 110,111 lung cancer, [112][113][114] pancreatic cancer, 107,[115][116][117] cholangiocarcinoma, 118 prostatic cancer, [119][120][121][122][123] bladder cancer, 124,125 kidney cancer, 125 cervical cancer, 126 ovarian cancer, [127][128][129][130] malignant melanoma, 131 osteosarcoma, 132 head-and-neck cancer,…”

“…Sema4D is associated with the etiology of various types of cancer 88,89 . Roles for Sema4D have been demonstrated in breast cancer, 90–101 colorectal carcer, 102–108 gastric cancer, 109 esophageal cancer, 110,111 lung cancer, 112–114 pancreatic cancer, 107,115–117 cholangiocarcinoma, 118 prostatic cancer, 119–123 bladder cancer, 124,125 kidney cancer, 125 cervical cancer, 126 ovarian cancer, 127–130 malignant melanoma, 131 osteosarcoma, 132 head‐and‐neck cancer, 133–137 medulloblastoma, 138 leukemia, 139–143 malignant lymphoma, 144 and multiple myeloma (Figure 4). 145 Cancer cells express Sema4D or its receptor, which are typically up‐ or down‐regulated in tumors compared to normal tissues.…”