Cellular and molecular mechanisms of non-coding RNAs in gastrointestinal malignancies

Abstract

Biliary tract cancers (BTC) stand out among gastrointestinal malignancies for their high mortality rates and limited treatment options, emphasizing the need for new molecular targets to guide the development of therapeutic strategies. In an effort to uncover novel regulatory networks involving non-coding RNAs, we focused on the miR-200 family, with its impact on the epithelial-mesenchymal transition (EMT) and its more recently described role in immune evasion mechanisms like immune checkpoint (IC) expression. We aimed to investigate the relationship between EMT and immune evasion in BTC, with the miR-200 family as potential regulatory interface. Initial analyses suggested a promising link between microRNA mimic-mediated miR-200c-3p overexpression and the upregulation of key ICs like LGALS9, PD-L1, and IDO1. However, when we noticed that neither miR-200c-3p knockdown, nor stable miR-200c-3p overexpression, or transient overexpression using a miR-200c-3p mimic from a different manufacturer had any effects, we questioned our original findings. This led to the hypothesis that the upregulation of ICs was not driven by the physiological action of miR-200c-3p, but rather by unspecific effects of the miR-200c-3p mimic itself. Shifting our research focus towards understanding the unintended miR-200c-3p mimic effect on ICs, we identified a strong involvement of double-stranded (ds)RNA-dependent innate immune responses. The miScript miR-200c-3p mimic, but not miR-200c-3p itself, lead to an upregulation of dsRNA sensors, interferons (IFNs), and antiviral effectors. Further analyses using a dsRNA analog poly(I:C) revealed the presence of IFN-β-mediated auto- and paracrine signaling involving Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) signaling pathway. Inhibiting JAK/STAT abrogated the effects of dsRNA-mediated immune responses on the upregulation of ICs, establishing this pathway as essential link between innate immune responses and the expression of ICs like LGALS9, PD-L1, and IDO1. Intriguingly, parts of these dsRNA-mediated effects were also observed when treating BTC cells with cisplatin. While the mechanisms behind the cisplatin-mediated IC upregulation remain mostly elusive, our data suggest a potential involvement of dsRNA-mediated innate immunity – a topic that will be addressed in future research.

Datum der Bewilligung	2024
Originalsprache	Englisch
Gradverleihende Hochschule	Medizinische Universität Graz
Betreuer/-in	Julia Kargl (Betreuer*in), Martin Pichler (Betreuer*in) & Beate Rinner (Betreuer*in)