Targeting cancer stem cells in multiple myeloma.

Multiple myeloma (MM) is a hematological malignancy of bone marrow (BM) plasma cells with excessive clonal expansion and is associated with the overproduction of light-chain or monoclonal immunoglobulins (Igs). MM remains incurable, with high rates of relapses and refractory disease after first-line treatment. Cancer stem cells (CSCs) have been implicated in drug resistance in MM; however, the evidence for CSCs in MM is not adequate, partly due to a lack of uniformity in the definitions of multiple myeloma stem cells (MMSCs). We review advances in understanding MMSCs and their role in drug resistance to MM therapies. We also discuss novel therapeutic strategies to overcome MMSC-mediated relapses and drug resistance.

The negative effect of antibiotics on RCC patients with immunotherapy: A systematic review and meta-analysis.

Background: Microbiome dysbiosis is considered a predictive biomarker of clinical response in renal cell carcinoma (RCC), which can be regulated by antibiotics (ATB). Multiple studies have shown that concomitant ATB administration has inhibitory effects on immunotherapy in RCC. This review aimed to assess the impact of ATB on patient survival and tumor response in RCC with immunotherapy. Methods: Literature evaluating the effect of ATB on immunotherapy in RCC from Cochrane Library®, PubMed®, Embase®, Scopus®, and Web of Science® were systematically searched. Hazard ratios (HR) for progression-free survival (PFS) and overall survival (OS), odds ratio (OR) for objective response rate (ORR) and primary progressive disease (PD) were pooled as effect sizes for clinical outcomes. Subgroup analysis was conducted to reveal the determinants of the effect of ATB on immunotherapy, including time windows of ATB exposure to immunotherapy initiation, ICIs treatment and study location. The leave-one-out approach was adopted to analyze the heterogeneity formulated. Cumulative meta-analysis adding by time was used to observe dynamic changes of the results. Results: Ten studies were included in the systematic review and six studies (with n=1,104 patients) were included in the meta-analysis, four studies were excluded for overlapping patients with subsequent larger studies and lack of unique patient-level data. ATB administration was significantly correlated with shorter PFS (HR=2.10, 95%CI [1.54; 2.85], I2 = 2% after omitting study Derosa et al, 2021 detected by leave-one-out approach), shorter OS (HR=1.69, 95%CI [1.34; 2.12], I2 = 25%) and worse ORR (OR=0.58, 95%CI [0.41; 0.84]), but no difference was observed in risk of PD (OR=1.18, 95%CI [0.97; 1.44]). No significant differences existed among the subgroups for determining the determinants of ATB inhibition. Conclusions: Concomitant ATB with immunotherapy was associated with worse PFS, OS and ORR in RCC. No publication bias was observed in this study. Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=349577, identifier CRD42022349577.

Oncolytic herpes simplex virus infects myeloma cells in vitro and in vivo.

Because most patients with multiple myeloma (MM) develop resistance to current regimens, novel approaches are needed. Genetically modified, replication-competent oncolytic viruses exhibit high tropism for tumor cells regardless of cancer stage and prior treatment. Receptors of oncolytic herpes simplex virus 1 (oHSV-1), NECTIN-1, and HVEM are expressed on MM cells, prompting us to investigate the use of oHSV-1 against MM. Using oHSV-1-expressing GFP, we found a dose-dependent increase in the GFP+ signal in MM cell lines and primary MM cells. Whereas NECTIN-1 expression is variable among MM cells, we discovered that HVEM is ubiquitously and highly expressed on all samples tested. Expression of HVEM was consistently higher on CD138+/CD38+ plasma cells than in non-plasma cells. HVEM blocking demonstrated the requirement of this receptor for infection. However, we observed that, although oHSV-1 could efficiently infect and kill all MM cell lines tested, no viral replication occurred. Instead, we identified that oHSV-1 induced MM cell apoptosis via caspase-3 cleavage. We further noted that oHSV-1 yielded a significant decrease in tumor volume in two mouse xenograft models. Therefore, oHSV-1 warrants exploration as a novel potentially effective treatment option in MM, and HVEM should be investigated as a possible therapeutic target.

Daratumumab induces mechanisms of immune activation through CD38+ NK cell targeting.

Daratumumab (Dara), a multiple myeloma (MM) therapy, is an antibody against the surface receptor CD38, which is expressed not only on plasma cells but also on NK cells and monocytes. Correlative data have highlighted the immune-modulatory role of Dara, despite the paradoxical observation that Dara regimens decrease the frequency of total NK cells. Here we show that, despite this reduction, NK cells play a pivotal role in Dara anti-MM activity. CD38 on NK cells is essential for Dara-induced immune modulation, and its expression is restricted to NK cells with effector function. We also show that Dara induces rapid CD38 protein degradation associated with NK cell activation, leaving an activated CD38-negative NK cell population. CD38+ NK cell targeting by Dara also promotes monocyte activation, inducing an increase in T-cell costimulatory molecules (CD86/80) and enhancing anti-MM phagocytosis activity ex vivo and in vivo. In support of Dara's immunomodulating role, we show that MM patients that discontinued Dara therapy because of progression maintain targetable unmutated surface CD38 expression on their MM cells, but retain effector cells with impaired cellular immune function. In summary, we report that CD38+ NK cells may be an unexplored therapeutic target for priming the immune system of MM patients.

The role of myeloid-derived suppressor cells in hematologic malignancies.

PURPOSE OF REVIEW: This article focuses on the immunosuppressive impact of myeloid-derived suppressor cells (MDSCs) and the potential clinical implications in hematological malignancies. RECENT FINDINGS: MDSCs play a critical role in the regulation of the immune response in cancer. They inhibit activation of adaptive immune response and as a result foster the growth of the malignancy. Recent studies have shown that MDSCs serve as prognostic biomarkers and as targets for cancer immunotherapy. Preclinical and clinical studies have identified new approaches to deplete MDSC populations and inhibit MDSC function with combination immunomodulatory therapies including chemotherapeutic agents with immune checkpoint-directed treatment. SUMMARY: A broad spectrum of publications indicate that direct targeting of MDSCs may abrogate their protumorigenic impact within the tumor microenvironment through activation of the adaptive immune response.

MiR-16 regulates crosstalk in NF-κB tolerogenic inflammatory signaling between myeloma cells and bone marrow macrophages.

High levels of circulating miR-16 in the serum of multiple myeloma (MM) patients are independently associated with longer survival. Although the tumor suppressor function of intracellular miR-16 in MM plasma cells (PCs) has been elucidated, its extracellular role in maintaining a nonsupportive cancer microenvironment has not been fully explored. Here, we show that miR-16 is abundantly released by MM cells through extracellular vesicles (EVs) and that differences in its intracellular expression as associated with chromosome 13 deletion (Del13) are correlated to extracellular miR-16 levels. We also demonstrate that EVs isolated from MM patients and from the conditioned media of MM-PCs carrying Del13 more strongly differentiate circulating monocytes to M2-tumor supportive macrophages (TAMs), compared with MM-PCs without this chromosomal aberration. Mechanistically, our data show that miR-16 directly targets the IKKα/ß complex of the NF-κB canonical pathway, which is critical not only in supporting MM cell growth, but also in polarizing macrophages toward an M2 phenotype. By using a miR-15a-16-1-KO mouse model, we found that loss of the miR-16 cluster supports polarization to M2 macrophages. Finally, we demonstrate the therapeutic benefit of miR-16 overexpression in potentiating the anti-MM activity by a proteasome inhibitor in the presence of MM-resident bone marrow TAM.

Daratumumab induces CD38 internalization and impairs myeloma cell adhesion.

Daratumumab (Dara), a human immunoglobulin G1 kappa (IgG1κ) monoclonal anti-CD38 antibody, has been approved by the U.S. Food and Drug Administration for the treatment of relapsed multiple myeloma (MM) as a single agent as well as in combination with immunomodulatory drugs (IMiDs) and proteasome inhibitors (PI). Although the scientific rationale behind the use of Dara in combination with IMiDs has been extensively explored, the molecular mechanisms underlying Dara-PI regimens have not yet been investigated. Here, we demonstrate that CD38 on the surface of MM cells is rapidly internalized after Dara treatment; we also show that Dara treatment impairs MM cell adhesion, an effect that can be rescued by using the endocytosis inhibitor Dynasore. Finally, we show that Dara potentiates bortezomib (BTZ) killing of MM cells in vitro and in vivo, independent of its function as an immune activator. In conclusion, our data show that Dara impairs MM cell adhesion, which results in an increased sensitivity of MM to proteasome inhibition.

Fibroblast growth factor receptor 4 Gly388 Arg polymorphism is not associated with pre-eclampsia in Turkish women.

AIM: The aim of this study was to assess the association between human fibroblast growth factor receptor 4 (FGFR4) Gly(388) Arg polymorphism and pre-eclampsia (PE) by carrying out a case-control study in Turkish women. MATERIALS AND METHODS: In the present study 159 PE patients and 161 controls were included. DNA was extracted from peripheral blood leukocyte and FGFR4 Gly(388) Arg polymorphism was investigated using polymerase chain reaction-restriction fragment length polymorphism methods. RESULTS: For Gly388Arg polymorphism of FGFR4 we found no significant association between controls and PE patients. The frequencies of GlyGly, GlyArg and ArgArg genotypes were 56.6%, 36.4% and 7% for the study group and 50.3%, 44.7% and 5% for the control group, respectively. The risk of women with the GlyArg (odds ratio = 0.7, 95% confidence interval: 0.45-1.14) and ArgArg (odds ratio = 1.2, 95% confidence interval: 0.47-3.22) genotypes for PE did not differ significantly from that of GlyGly genotype carriers. CONCLUSION: As we could not find any association between genetic variability in Gly(388) Arg of FGFR4 and PE, this specific polymorphism of FGFR4 can be eliminated as a risk factor for PE at least for Turkish women.

AXIN2 polymorphism and its association with prostate cancer in a Turkish population.

Polymorphism of AXIN2, a component of Wnt signaling, has been shown to play a role in tumorigenesis and dysregulated in cancer cells. In order to find out if AXIN2 polymorphism is a risk factor for prostate cancer, we analyzed eight polymorphic regions of this gene in 84 patients with prostate cancer and compared the results with 100 healthy controls in a Turkish population using PCR-RFLP methods. The genotype frequencies and risk factors of prostate cancer and control groups were analyzed by Chi-square test. We found a statistically significant result between prostate cancer risk and AXIN2 Intron2-956+16A/G (rs35285779) SNP. The frequency of the homozygous G/G (0%) and heterozygous A/G (18%) genotypes was significantly less in patients with prostate cancer than in healthy controls (7 and 32%, respectively) (P<0.05) for this SNP. When compared with the wild-type A/A genotype of the controls, prostate cancer patients with the A/G and G/G genotype showed reduced risk of cancer; the adjusted odds ratio (OR) for patients with the homozygous G/G genotype was 0.87 (95% CI: 0.81-0.95) and for heterozygous A/G genotype was 0.42 (95% CI: 0.20-0.85). We found no statistically significant association between controls and prostate cancer for other seven SNPs of AXIN2 including Exon1-148 C/T (rs2240308), Exon1-432 T/C (rs2240308), Exon5-1365 G/A (rs9915936), Exon5-1386 C/T (rs1133683), Intron5-1712+19 T/G, Exon7-2062 C/T, and Intron7-2141+73 G/A (rs4072245) (P>0.05). These results suggest that the AXIN2 Intron2 rs35285779 SNP is associated with development of prostate cancer as a protective SNP, while an association between other seven SNPs of the AXIN2 and risk of prostate cancer was not observed.

AXIN2 polymorphism and its association with astrocytoma in a Turkish population.

The product of AXIN2, a component of Wnt signalling, plays a role in tumorigenesis and is dysregulated in cancer cells. In order to determine whether the AXIN2 polymorphism is a risk factor for astrocytoma, we analysed eight polymorphic regions of this gene in 100 astrocytoma patients compared to 100 healthy controls in a Turkish population using PCR-RFLP methods. For the Exon1-148 T/C, Exon1-432 C/T, Exon5-1365 G/A, Intron5-1712+19G/T, Exon7-2062 C/T and Intron7-2141+73 G/A SNPs of AXIN2, no significant association between controls and astrocytoma patients was found. For the Exon5-1386 C/T SNP, a statistically significant association between controls and patients was found (p<0.05). For this astrocytoma, patients with the TT genotype showed an increased risk with an OR of 2.92 (adjusted for age, gender and smoking status) (95% CI 1.14-7.47) as compared to the controls with the CC genotype. Our results suggest that AXIN2 SNPs may be associated with astrocytoma.