(PA-255) Multi-hit Cytogenetics Risk Events Associated with IFN-I Suppression across TME of NDMM Patients and Poor Outcomes

Multiple myeloma (MM) is a heterogeneous malignancy, with patients often exhibiting high-risk cytogenetic abnormalities linked to poor outcomes. While alterations such as t(4;14) and gain of 1q are well studied, emerging evidence suggests that the cumulative presence of multiple cytogenetic hits has a greater negative prognostic impact than single events. The mechanisms by which these co-occurring alterations affect the bone marrow microenvironment and drive progression remain unclear. We hypothesize that multiple high-risk events remodel the immune microenvironment, promoting disease progression and adverse outcomes.

Methods:

To investigate the impact of multi-hit cytogenetic events on the immune microenvironment, we analyzed scRNA-seq data from 337 newly diagnosed MM patients generated as part of the Immune Atlas initiative. Cytogenetic alterations of these patients were derived from whole-genome and whole-exome sequencing of CD138⁺ bone marrow aspirates from the CoMMpass cohort. Patients were classified as having multi-hit high-risk disease if they exhibited either (i) two high-risk cytogenetic events—such as NSD2 t(4;14), MAF t(14;16), or del(17p13)—or (ii) one high-risk event in combination with gain of 1q21.

Results:

Based on cytogenetics information, we stratified 33 as ‘multi-hit’ high-risk and 34 as single-hit high-risk. Multi-hit high-risk status was significantly associated with worse progression-free survival (PFS) compared to standard-risk patients, even after adjusting for age, treatment regimen, and autologous stem cell transplant (ASCT) status (HR=2.34, p< 7.2e-5). In contrast, single-hit high-risk patients showed a non-significant trend toward inferior PFS (HR=1.51, p=0.071). The most frequent multi-hit combination involved NSD2 translocation [t(4;14)] and gain of 1q21, observed in 23 patients. ScRNA-seq Immune clusters analysis revealed that multi-hit patients exhibited marked reductions in several IFN-I-stimulated CD4⁺ and CD8⁺ T cell subsets, accompanied by decreased expression of antiviral response markers such as ISG15, XAF1, and IFI44L. These patients also displayed a significant enrichment of inflammatory CD16⁺ non-classical monocytes. These immune alterations were significantly different from both single-hit high-risk and standard-risk cohorts. Further stratification of patients harboring both NSD2 and 1q21 revealed a distinct enrichment of late-activated, cytotoxic CD8⁺ and CD4⁺ T cells, not seen in patients with NSD2 or 1q21 alone. Enrichment of these populations correlated with rapid MM progression. Secondary analyses suggested that suppression of IFN-I signaling is primarily driven by the presence of 1q21 in combination with another high-risk lesion. Suppression was observed across multiple immune and malignant populations in the scRNA-seq and paired bulk RNA tumor datasets.

Conclusions:

Patients with multiple multi-hit high risk myeloma display distinct immunologic traits from patients with standard risk or single-hit high risk myelomas.