Exploring the capability of mutant SRSF2 to elicit an innate immune response in myeloid malignancies

Abstract

DNA damage repair deficiencies (DDRD) can elicit innate immune responses via activation of the cytosolic dsDNA sensing cGAS/STING pathway. However, this pathway can also induce the up-regulation of immune checkpoint proteins, such as PD-L1, suggesting potential benefits for the use of immune checkpoint inhibitors (ICIs) in DDRD-positive tumours. Our lab has previously demonstrated that mutations in SF3B1, a component of the spliceosome complex, conferred a DDRD, suggesting a role for the spliceosome in DNA damage repair. Spliceosome mutations frequently occur in myeloid malignancies, such as myelodysplastic syndromes (MDS) and acute myeloid leukaemia (AML). This study aimed to explore whether mutations in another commonly mutated spliceosome component, SRSF2, confers a DDRD and whether this could be exploited for combination therapies with ICIs. A CRISPR/Cas9-genertaed isogenic K-562 model harbouring the common SRSF2P95H mutation was used throughout this study. Immunofluorescence imaging of 53BP1 and RAD51 post-irradiation treatment revealed that SRSF2P95H cells have a reduced ability to repair DNA damage, suggesting a potential DDRD. Importantly, DNA damage induction via daunorubicin treatment led to significant increases in micronuclei and cytosolic dsDNA, as well as elevated inflammatory cytokine transcription (CCL5, IFIT2 and CXCL10) and secretion (CCL5) in SRSF2P95H cells compared to WT comparators. However, no significant reductions in cytokine transcription or secretion were observed following depletion of STING but were significantly reduced following depletion of the dsRNA sensing adaptor, MAVS. Indeed, cytosolic dsRNA was observed following daunorubicin treatment in SRSF2P95H cells. To assess the potential of therapeutic benefit of combining daunorubicin with ICIs, the immune competent chorioallantoic membrane (CAM) model was utilised. Unexpectedly, ICI with nivolumab induced more aggressive tumour growth, In conclusion, this study revealed that SRSF2P95H mutant cells have an increased ability to elicit an innate immune response compared to WT counterparts. However, the response may be reliant on the MAVS-dependent pathway rather than the STING pathway. With further investigation, this data is pathing the way for the use of SRSF2 mutational status as a biomarker for ICIs.

Thesis is embargoed until 31 July 2030.

Date of Award	Jul 2025
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Katrina Lappin (Supervisor) & Kienan Savage (Supervisor)