We have explored the potential role of genetics in the development of osteonecrosis of the jaw (ONJ) in multiple myeloma (MM) patients under bisphosphonate therapy. A genome-wide association study was performed using 500 568 single nucleotide polymorphisms (SNPs) in 2 series of homogeneously treated MM patients, one with ONJ (22 MM cases) and another without ONJ (65 matched MM controls). Four SNPs (rs1934951, rs1934980, rs1341162, and rs17110453) mapped within the cytochrome P450-2C gene (CYP2C8) showed a different distribution between cases and controls with statistically significant differences (P = 1.07 × 10⁻⁶, P = 4.231 × 10⁻⁶, P = 6.22 × 10⁻⁶, and P = 2.15 × 10⁻⁶, respectively). SNP rs1934951 was significantly associated with a higher risk of ONJ development even after Bonferroni correction (P corrected value = .02). Genotyping results displayed an overrepresentation of the T allele in cases compared with controls (48% vs 12%). Thus, individuals homozygous for the T allele had an increased likelihood of developing ONJ (odds ratio 12.75, 95% confidence interval 3.7-43.5).

We have analyzed the applicability, sensitivity and prognostic value of allele-specific oligonucleotide real-time quantitative PCR (ASO RQ-PCR) as a method for minimal residual disease (MRD) assessment in patients with multiple myeloma (MM), comparing the results with those of multiparameter flow cytometry (MFC). A total of 170 patients enrolled in three consecutive Spanish trials achieving at least partial response after treatment were included. Lack of clonality detection (n=31), unsuccessful sequencing (n=17) and suboptimal ASO performance (n=51) limited the applicability of PCR to 42% of cases. MRD was finally investigated in 103 patients (including 32 previously studied) with persistent disease identified by PCR and MFC in 54% and 46% of cases, respectively. A significant correlation in MRD quantitation by both the techniques was noted (r=0.881, P<0.001), being reflective of treatment intensity. Patients with <10⁻⁴ residual tumor cells showed longer progression-free survival (PFS) compared with the rest (not reached (NR) vs 31 months, P=0.002), with similar results observed with MFC. Among complete responders (n=62), PCR discriminated two risk groups with different PFS (49 vs 26 months, P=0.001) and overall survival (NR vs 60 months, P=0.008). Thus, although less applicable than MFC, ASO RQ-PCR is a powerful technique to assess treatment efficacy and risk stratification in MM.

Detecting persistent minimal residual disease (MRD) allows the identification of patients with an increased risk of relapse and death. In this study, we have evaluated MRD 3 months after transplantation in 106 myeloma patients using a commercial next-generation sequencing (NGS) strategy (LymphoTrack®), and compared the results with next-generation flow (NGF, EuroFlow). The use of different marrow pulls and the need of concentrating samples for NGS biased the applicability for MRD evaluation and favored NGF. Despite that, correlation between NGS and NGF was high (R² = 0.905). The 3-year progression-free survival (PFS) rates by NGS and NGF were longer for undetectable vs. positive patients (NGS: 88.7% vs. 56.6%; NGF: 91.4% vs. 50%; p < 0.001 for both comparisons), which resulted in a 3-year overall survival (OS) advantage (NGS: 96.2% vs. 77.3%; NGF: 96.6% vs. 74.9%, p < 0.01 for both comparisons). In the Cox regression model, NGS and NGF negativity had similar results but favoring the latter in PFS (HR: 0.20, 95% CI: 0.09–0.45, p < 0.001) and OS (HR: 0.21, 95% CI: 0.06–0.75, p = 0.02). All these results reinforce the role of MRD detection by different strategies in patient prognosis and highlight the use of MRD as an endpoint for multiple myeloma treatment.

Background Recent findings suggest that a specific deletion of Dicer1 in mesenchymal stromal cell-derived osteoprogenitors triggers several features of myelodysplastic syndrome in a murine model. Our aim was to analyze DICER1 and DROSHA gene and protein expression in mesenchymal stromal cells (the osteoblastic progenitors) obtained from bone marrow of myelodysplastic syndrome patients, in addition to microRNA expression profile and other target genes such as SBDS, a DICER1-related gene that promotes bone marrow dysfunction and myelodysplasia when repressed in a murine model. Mesenchymal stromal cells from 33 bone marrow samples were evaluated. DICER, DROSHA and SBDS gene expression levels were assessed by real-time PCR and protein expression by Western blot. MicroRNA expresion profile was analyzed by commercial low-density arrays and some of these results were confirmed by individual real-time PCR. Mesenchymal stromal cells from myelodysplastic syndrome patients showed lower DICER1 (0.65±0.08 vs. 1.91±0.57; P=0.011) and DROSHA (0.62±0.06 vs. 1.38±0.29; P=0.009) gene expression levels, two relevant endonucleases associated to microRNA biogenesis, in comparison to normal myelodysplastic syndrome. These findings were confirmed at protein levels by Western blot. Strikingly, no differences were observed between paired mononuclear cells from myelodysplastic syndrome and controls. In addition, mesenchymal stromal cells from myelodysplastic syndrome patients showed significant lower SBDS (0.63±0.06 vs. 1.15±0.28; P=0.021) gene expression levels than mesenchymal stromal cells from healthy controls. Furthermore, mesenchymal stromal cells from myelodysplastic syndrome patients showed an underlying microRNA repression compared to healthy controls. Real-time PCR approach confirmed that mir-155, miR-181a and miR-222 were down-expressed in mesenchymal stromal cells from myelodysplastic syndrome patients. Conclusions This is the first description of an impaired microRNA biogenesis in human mesenchymal stromal cells from myelodysplastic syndrome patients, where DICER1 and DROSHA gene and protein downregulation correlated to a gene and microRNA abnormal expression profile, validating the animal model results previously described.