Anti‐pyroptotic function of TGF‐β is suppressed by a synthetic dsRNA analogue in triple negative breast cancer cells

Abstract

Development of innovative therapeutic modalities would address an unmet clinical need in the treatment of triple negative breast cancer (TNBC). Activation of retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) such as melanoma differentiation-associated gene 5 (MDA5) and RIG-I in cancer cells is suggested to suppress tumor progression by inducing cell death. Transfection of polyI:C, a conventionally used synthetic double-stranded RNA (dsRNA) analogue that activates RLRs, has been evaluated in clinical trials. However, detailed mechanisms of tumor suppression by RLRs, especially interactions with other signaling pathways, remain elusive. Here, we showed that transfection of polyI:C suppressed transforming growth factor-b (TGF-b) signaling in a MDA5-and RIG-I-dependent manner. We found that suppression of TGF-b signaling by polyI:C promoted cancer cell death, which was attenuated by forced expression of constitutively active Smad3. More detailed analysis suggested that cell death by polyI:C transfection exhibited characteristics of pyroptosis, which is distinct from apoptosis. Therapeutic efficacy of polyI:C transfection was also demonstrated using a mouse model. These results indicated that intratumor administration of polyI:C and related dsRNA analogues may be promising treatments for TNBC through inhibition of the anti-pyroptotic function of TGF-b.

PolyI:C attenuates transforming growth factor‐β signaling to induce cytostasis of surrounding cells by secreted factors in triple‐negative breast cancer

“…We then confirmed our findings by using another TNBC cell line, Hs578T. Hs578T cells were also prone to polyI:C‐induced cell death, partly through the inhibition of TGF‐β signaling, in our previous study 9 . Hs578T cells stably expressing either caSmad3 (Hs578T‐caSmad3) or HA (Hs578T‐HA) were established, and we found that caSmad3 expression in Hs578T cells inhibited IFNB1 induction by polyI:C (Figure 2F).…”

“…We then established BT‐549 cells with Smad3 gene inactivation to evaluate the contribution of the endogenous signaling pathway to inhibit polyI:C‐induced IFNB1 expression and cytostasis. Of note, Smad3 was phosphorylated at baseline in both BT‐549 and Hs578T cells, 9 but too weak to detect, depending on the experimental condition (Figure 5A). Stable Smad3 gene inactivation was achieved by lentivirus‐based gRNA expression (Figure 5A).…”

“…The above results suggested that the canonical target genes of the IFN signaling regulated by IRF3 were inhibited by Smad signaling in TNBC cells, which was efficiently suppressed by polyI:C in the present in vitro culture condition. Because TGFβ signaling is activated in some of the TNBC tumors in vivo, 9,23,24 the present findings suggest the importance of considering the activation of this signaling pathway for the selection of patients to treat with polyI:C.…”

A Novel Pyroptosis-Associated Long Non-coding RNA Signature Predicts Prognosis and Tumor Immune Microenvironment of Patients With Breast Cancer

“…TGF-β signaling is an important pathway in cancers and has both tumor-promoting and tumor inhibiting functions. It has been reported that TGF-β can suppress pyroptosis ( Tamura et al, 2021 ). In this study, enrichment of TGF-β signaling pathway and TGF-β family members were observed in the high-risk group.…”

The Pyroptosis-Related 9 LncRNA Signature and LncRNA-miRNA-mRNA Regulatory Network in Breast Cancer: A Comprehensive Analysis Based On TCGA Database

“…The ECM receptor interaction was found to participate in the proliferation and invasion of kidney cancer cells 55 . It was also reported that TGF-β suppressed pyroptosis in triple-negative breast cancer 56 , and wnt/β-catenin participated in the metastasis of breast cancer 57 .…”