1662P - Targeting stress granule formation as a synthetic lethality strategy for kras-induced pancreatic cancer initiation

Background

Stress granules (SGs) are membrane-less organelles formed by liquid-liquid phase separation (LLPS) that play a critical role in regulating RNA metabolism, and protein synthesis, in a wide range of stress responses. These granules are required to support pancreatic cancer (PDAC) transformation, cell survival, growth, and chemotherapy resistance, making them an attractive target for new cancer therapies. Here we report a novel mechanism for SG formation, which is induced by NUPR1 (an intrinsically disordered stress-associated protein), in response to Kras ^G12D oncogenic stress. We provide a preclinical proof of concept for using SG inhibition as an efficient strategy for targeting PDAC initiation and development, by using NUPR1 inhibitors.

Methods

We have used recombinant proteins for in vitro tests (LLPS tests), PDAC-derived cell lines, and doxycycline-inducible transgenic cell lines (cell viability tests, evaluation of gene expression, and SGs quantification), a transgenic Pdx1-Cre; LSL-Kras ^G12D mouse model.

Results

In this study, we show that NUPR1, has the capacity to produce droplets through LLPS, but not its mutants or under the treatment of its inhibitor (ZZW-115). We observed that LLPS induced by rNUPR1 is essential for SGs formation since genetic or pharmacological inhibition of NUPR1 activity hampers SGs formation in pancreatic cancer cells. In addition, we found that Kras ^G12D mutation causes significant oncogenic stress which in turn induces a strong overexpression of NUPR1, promoting the formation of SGs as a stress-dependent mechanism of cell survival. Consistently, forced Kras^G12D expression in pancreatic cells elicits a strong sensitivity to NUPR1 inactivation by genetic or pharmacological means. Finally, inhibition of SGs formation with the NUPR1 inhibitor ZZW-115 in Pdx1-Cre; LSL-Kras ^G12D mice blocks the transformation process indicating that SGs formation is necessary for PDAC development.

Conclusions

In this work, we provide a preclinical proof of concept showing that SG formation is a targetable step in the Kras ^G12D signaling pathway, thus suggesting that inhibiting NUPR1 or SG formation can be utilized as a synthetic lethality therapeutic strategy for Kras ^G12D -dependent tumors.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

ARC.

Disclosure

All authors have declared no conflicts of interest.