Current perspectives on interethnic variability in multiple myeloma: Single cell technology, population pharmacogenetics and molecular signal transduction

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This review discusses the emerging single cell technologies and applications in Multiple myeloma (MM), population pharmacogenetics of MM, resistance to chemotherapy, genetic determinants of drug-induced toxicity, molecular signal transduction.

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The role(s) of epigenetics and noncoding RNAs including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) that influence the risk and severity of MM are also discussed.

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It is understood that ethnic component acts as a driver of variable response to chemotherapy in different sub-populations globally.

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This review augments our understanding of genetic variability in ‘myelomagenesis’ and drug-induced toxicity, myeloma microenvironment at the molecular and cellular level, and developing precision medicine strategies to combat this malignancy.

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The emerging single cell technologies hold great promise for enhancing our understanding of MM tumor heterogeneity and clonal diversity.

Multiple myeloma (MM) is an aggressive cancer characterised by malignancy of the plasma cells and a rising global incidence. The gold standard for optimum response is aggressive chemotherapy followed by autologous stem cell transplantation (ASCT). However, majority of the patients are above 60 years and this presents the clinician with complications such as ineligibility for ASCT, frailty, drug-induced toxicity and differential/partial response to treatment. The latter is partly driven by heterogenous genotypes of the disease in different subpopulations. In this review, we discuss emerging single cell technologies and applications in MM, population pharmacogenetics of MM, resistance to chemotherapy, genetic determinants of drug-induced toxicity, molecular signal transduction, as well as the role(s) played by epigenetics and noncoding RNAs including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) that influence the risk and severity of the disease. Taken together, our discussions further our understanding of genetic variability in ‘myelomagenesis’ and drug-induced toxicity, augment our understanding of the myeloma microenvironment at the molecular and cellular level and provide a basis for developing precision medicine strategies to combat this malignancy.

Recent advances in multiple myeloma: a Korean perspective

Epidemiologically, multiple myeloma (MM) is a malignant disorder of plasma cells with a higher incidence among Western populations than among Asians. However, there is growing evidence of a recent increase in the age-standardized incidence rate (ASR) of MM in Asian countries, particularly Korea. Application of novel agents has resulted in significant improvement of treatment outcomes, and the advances are ongoing with the recent introduction and U.S. Food and Drug Administration's approval of newer agents, including carfilzomib, ixazomib, elotuzumab, and daratumumab. In concert with the technical advances in the cytogenetic and molecular diagnostics of MM, modifications of its diagnosis and staging system have been attempted for better risk stratification. The modified diagnostic criteria from the International Myeloma Working Group in 2014 enabled a strategy of more active treatment for some patients with smoldering MM, with an ultra-high risk of progression, and fine-tuned the definition of end-organ damage, known as CRAB (hypercalcemia, renal insufficiency, anemia, and bone lesions). Considering Korea's trend of aging at an unprecedented rate, we can expect that the ASR of MM will maintain a gradual increase for many years to come; therefore, MM will be a cancer of critical importance from both medical and socioeconomic perspectives in Korea.

Clinical profiles of multiple myeloma in Asia-An Asian Myeloma Network study

The incidence of multiple myeloma (MM) is known to be variable according to ethnicity. However, the differences in clinical characteristics between ethnic groups are not well-defined. In Asian countries, although the incidence of MM has been lower than that of Western countries, there is growing evidence that MM is increasing rapidly. The Asian Myeloma Network decided to initiate the first multinational project to describe the clinical characteristics of MM and the clinical practices in Asia. Data were retrospectively collected from 23 centers in 7 countries and regions. The clinical characteristics at diagnosis, survival rates and initial treatment of 3,405 symptomatic MM patients were described. Median age was 62 years (range, 19-106), with 55.6% of being male. Median overall survival (OS) was 47 months (95% CI 44.0-50.0). Stem cell transplantation was performed in 666 patients who showed better survival rates (79 vs. 41 months, P < 0.001). The first-line treatments of 2,970 patients were analyzed. The overall response rate was 71% including very good partial response or better in 31% of the 2,660 patients those were able to be evaluated. New drugs including bortezomib, thalidomide, and lenalidomide were used in 36% of 2,970 patients and affected OS when used as a first-line treatment.

MyelomA Genetics International Consortium

While the etiology of multiple myeloma (MM) is largely unknown, evidence for an inherited genetic susceptibility is provided by the two-fold increased risk of the disease seen in first-degree relatives of cases of MM. It is likely that part of this heritable risk is a consequence of the co-inheritance of low-risk genetic variants. The accumulated experience to date in identifying risk variants for other tumors has highlighted difficulties in conducting statistically and methodologically rigorous studies. The MyelomA Genetics International Consortium (MAGIC) includes 16 research groups in Europe, Asia, Australasia, the Middle East and the Americas engaged in studying the genetics of MM. The first goal of MAGIC is to identify and characterize common genetic variants for MM through association-based analyses. Here, we review the rationale for identifying genetic risk variants for MM and our proposed strategy for establishing MAGIC.

Protective role of CYP1A1*2A in the development of multiple myeloma

We had previously reported the association of the NQO1*2/*2 polymorphism with a decreased risk for multiple myeloma (MM) in Koreans (odds ratio, OR, 0.24; 95% confidence interval, CI, 0.01-0.68). The associations of polymorphisms of other metabolizing enzymes (CYP1A1, GSTM1 and GSTT1) with the MM risk were investigated in 116 Korean MM patients and 176 Korean controls using TaqMan allelic discrimination and multiplex polymerase chain reaction. The ORs for CYP1A1*1/*2A and CYP1A1*1/*2B genotypes were 0.43 (95% CI, 0.19-0.98) and 0.51 (95% CI, 0.26-0.98), respectively, which was significantly associated with a decreased MM risk. With regard to CYP1A1 alleles, the OR for the CYP1A1*2A allele was 0.57 (95% CI, 0.326-0.995), which was also significantly associated with a decreased MM risk. However, null types of GSTM1 and GSTT1 polymorphisms were not associated with the MM risk. These results were different from those of a previous report on Caucasians which suggested the association of the GSTT1 polymorphism with an increased MM risk and no association of CYP1A1 with the MM risk. The associations of polymorphisms of metabolizing enzymes with the risk for MM differed between Koreans and Caucasians, suggesting an ethnic variation in the susceptibility to MM.