Ten Year Survival in Patients with Myeloma Is Characterized by the Persistence of Immunological Control Which Is Detected by Immunological Biomarkers

Abstract 1818

There is clinical evidence for the presence of a limited degree of host-tumor control in patients with multiple myeloma (MM) but the exact mechanisms involved are not known. Patients who survive for more than ten years are likely to have the most active immunological host-tumour control and are an ideal cohort to study. We now add to our preliminary observations using a range of immunological biomarkers in the 29 of these patients who attend our clinic.

51% of MM patients (n=264) had expanded CD3+CD8+ TCRVβ+ CD57+T cell clones detected by TCRVβ analysis (Beckman, BetaMark). Clonality was confirmed by IgH CDR3 sequencing. These clones accounted for 14.3% (median) of the CD3 cells (range 4–49%). CFSE tracking demonstrated the anergic nature of these clonal T cells (median 6% proliferation) compared with other CD8 cells (70% proliferation) while Geneset analysis of mRNA microarrays (Affymetrix U133) identified that anergy was caused by upregulated RAS, CSK, TOB and suppressed ERK pathways. Unlike recent reports for T-LGL, microarray analysis suggested that there was no evidence of STAT3 upregulation in the MM T cell clones. Functional studies suggested that these non-proliferating clones have split anergy as interferon-γ production was normal. In contrast, all ten year survivors had expanded T cell clones and serial studies demonstrated a >8 year persistence of the same clone in 8 out of 12 patients studied. More importantly, unlike the other MM patients, the T cell clones in 19 out of 21 of the ten year survivors studied were not anergic. The Treg/Th17 ratio in the ten year survivors was significantly lower than other MM patients (median 1.9 vs 12.0; p<0.0002) and even lower than age matched normals (median 5.6; p<0.006). This difference in the ten year survivors was due to an increased absolute Th17 cell (p<0.005) number and a reduced absolute T_regnumber (p<0.05). MM patients had a reduced number of absolute 6-Sulfo-LacNAc (SLAN)-DCs, a major source of IL-12, compared to both age matched controls and long term survivors (p < 0.01). Allo SLAN-DCs stimulated a higher proliferative response by MM T cells than could be achieved with mononuclear preparations.

In conclusion, MM patients have expanded clones of cytotoxic T cells that exhibit split anergy and these cells are potential candidates for restoring immunological control of MM and other cancers. The normalised T_reg/Th17 ratio suggests that the induced tolerance associated with increased T_reg cell numbers is also absent in these patients. Our observations that the ten year MM survivors do not have anergy in their clonal T cells and have less Treg suppression offers a unique cohort for future studies.