Decreased STING predicts adverse efficacy in bortezomib regimens and poor survival in multiple myeloma.

Purpose: STING (stimulator of interferon genes) is involved in viral and bacterial defense through interferon pathway and innate immunity. Increased susceptibility to infection is a common manifestation of multiple myeloma (MM). Thus, we aimed to explore the clinical significance and possible mechanism of STING in MM.

Materials And Methods: Immunohistochemistry and qPCR were used to detect STING expression in the bone marrow of MM patients, and flow cytometry was used to detect the amount of intracellular STING. All data were analyzed with clinical characteristics.

Results: STING expression was remarkably reduced in MM tissues compared to normal tissues and was not associated with stage. Multivariate analysis identified STING as an independent prognostic factor in MM patients (P = 0.001). In the bortezomib-containing regimens, patients with low STING expression were more difficult to achieve remission. A model incorporating STING and m-SMART significantly improved the predictive accuracy of overall survival in bortezomib regimens (AUC, 0.511 to 0.630, P = 0.044). Bortezomib efficacy has been reported to correlate with activated immunity, but the low expression group manifested as immune apathy. Although baseline characteristics showed intergroup differences in infection, the low expression group had an increased proportion of bacterial infections (1.7-fold) and a prolonged duration of antibiotic/antifungal medication (3.55 additional days); these patients were accompanied by a decreased neutrophil-to-lymphocyte ratio (NLR) and rarely activated neutrophils and leukocytes. The intracellular STING ratio was also defective in neutrophil-dominated leukocytes.

Conclusion: Our study revealed that STING had a strong association with bortezomib and could serve as a potential target for immunotherapy in multiple myeloma.