Chronic lymphocytic leukemia in China

Immunoglobulin gene rearrangements in Chinese and Italian patients with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in the Western world, whereas in Asia the incidence is about 10 times lower. The basis for this ethnic and geographic variation is currently unknown. The aim of this study was to characterize IGHVDJ rearrangements and stereotype of the HCDR3 region in a series of 623 Chinese CLL, in order to identify possible differences in immunoglobulin gene usage and their potential pathogenetic implications. Chinese CLL were compared to 789 Italian CLL. Chinese patients showed a higher proportion of mutated IGHV and a more frequent usage of IGHV3-7, IGHV3-74, IGHV4-39 and IGHV4-59 genes. A significantly lower usage of IGHV1-69 and IGHV1-2 was documented, with comparable IGHV3-21 frequency (3% Chinese vs 3.8% Italian CLL). The proportion of known stereotyped receptors was significantly lower in Chinese (19.7%) than in Italian CLL (25.8%), despite a significantly higher frequency of subset #8 (p= 0.0001). Moreover, new paired clusters were identified among Chinese cases. Overall, these data support a potential different antigenic exposure between Eastern and Western CLL.

Chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is the most common leukaemia among the adults in the Western World. CLL (and the corresponding nodal entity small lymphocytic lymphoma, SLL) is classified as a lymphoproliferative disorder characterised by the relentless accumulation of mature B-lymphocytes showing a peculiar immunophenotype in the peripheral blood, bone marrow, lymph nodes and spleen. CLL clinical course is very heterogeneous: the majority of patients follow an indolent clinical course with no or delayed treatment need and with a prolonged survival, while others experience aggressive disease requiring early treatment followed by frequent relapses. In the last decade, the improved understanding of CLL pathogenesis shed light on premalignant conditions (i.e., monoclonal B-cell lymphocytosis, MBL), defined new prognostic and predictive markers, improving patient stratification, but also broadened the therapeutic armamentarium with novel agents, targeting fundamental signaling pathways.

The mystery of chronic lymphocytic leukemia (CLL): Why is it absent in Asians and what does this tell us about etiology, pathogenesis and biology?

Chronic lymphocytic leukemia/small lymphocytic lymphoma is common in persons of predominately European descent but rare in Asians. Why is unknown but is likely genetically-determined. Environmental factors may also operate but are likely to be less important. When CLL occurs in Asians it has different features than CLL in persons of predominately European descent. The reason(s) for this is also not understood. We reviewed data on CLL in Asians (mostly Han Chinese but also other ethnic groups) and compared these data with those from persons of predominately European descent with CLL. CLL incidence was about 5-10-fold less in Asians. Asians with CLL are younger, have atypical morphologic and immunologic features, an increased proportion of IGHV mutations and rearrangements and briefer freedom-from-progression than persons of predominately European descent with CLL. These observations provide clues to the etiology and biology of CLL. But the mystery continues; more research is needed.

Fine-mapping of HLA associations with chronic lymphocytic leukemia in US populations

Chronic lymphocytic leukemia (CLL) displays remarkable ethnic predisposition for whites, with relative sparing of African-American and Asian populations. In addition, CLL displays among the highest familial predispositions of all hematologic malignancies, yet the genetic basis for these differences is not clearly defined. The highly polymorphic HLA genes of the major histocompatibility complex play a central role in immune surveillance and confer risk for autoimmune and infectious diseases and several different cancers, the role for which in the development of CLL has not been extensively investigated. The National Marrow Donor Program/Be The Match has collected HLA typing from CLL patients in need of allogeneic hematopoietic stem cell transplant and has recruited millions of volunteers to potentially donate hematopoietic stem cells. HLA genotypes for 3491 US white, 397 African-American, and 90 Hispanic CLL patients were compared with 50 000 controls per population from the donor registry. We identified several HLA alleles associated with CLL susceptibility in each population, reconfirming predisposing roles of HLA-A*02:01 and HLA-DRB4*01:01 in whites. Associations for haplotype DRB4*01:01∼DRB1*07:01∼DQB1*03:03 were replicated across all 3 populations. These findings provide a comprehensive assessment of the role of HLA in the development of severe CLL.

Genetic susceptibility for chronic lymphocytic leukemia among Chinese in Hong Kong

The genetic basis of chronic lymphocytic leukemia (CLL) has not been fully elucidated to date. Although it is the most common haematological malignancy in Caucasians, it is uncommon among Asians. A recent genome-wide scan of CLL in Caucasians, which was carried out in the UK, identified six variants showing strong association. We attempted to replicate these findings in 71 patients with CLL and 1273 controls in Hong Kong Chinese. Three of the six variants were significantly associated with CLL. The rs872071 variant (Odds Ratio (95% Confidence Interval) = 1.78 (1.25-2.53), P = 0.0013) in the IRF4 gene region showed the strongest association, similar to that reported in the UK study. Polymorphisms in SP140 and ACOXL were also associated with risk of CLL. Further, the mean allele frequencies of the six variants were moderately (59%) to extremely (0.5%) lower in the Chinese population compared with Caucasians. These results suggest that variants in three loci may contribute to risk of CLL among Chinese.

Characterization of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) in Shanghai, China: molecular and cytogenetic characteristics, IgV gene restriction and hypermutation patterns

The clinical, cytogenetic and molecular features of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), a disease previously considered to be rare in Asia, were examined in consecutive series of 70 cases diagnosed by our laboratory over a 30-month period. Clonal abnormalities were observed in 80% of CLL/SLL cases using a combination of conventional cytogenetic and fluorescence in situ hybridization (FISH) analysis. Those involving 14q32/IGH were the most frequent (24 cases), followed by trisomy 12 and 11q abnormalities. IgV(H) gene usage was non-random with over-representation of V(H)4-34, V(H)3-23 and a previously unreported increase in V(H)3-48 gene use. Somatic hypermutation (SHM) of IgV(H) germline sequences was observed in 56.5% of cases with stereotyped patterns of SHM observed in V(H)4-34 heavy chain complimentary-determining (HCDR1) and framework region CFR2 sequences. These findings in a Chinese population suggest subtle geographical differences in IgV(H) gene usage while the remarkably specific pattern of SHM suggest that a relatively limited set of antigens may be involved in the development of this disease worldwide. IgV(H) gene mutation status was a significant predictor of initial survival in CLL/SLL. However, an influence of karyotype on prognosis was not observed.

Chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia in the western world and is due to the accumulation of mature B lymphocytes in the peripheral blood, bone marrow and secondary lymphoid organs. The leukemic cells show a distinct phenotype, which is essential to reach the correct diagnosis. Despite the phenotypic homogeneity, the clinical outcome may be significantly different. Some patients have an indolent leukemia, with long survival while others experience an aggressive disease, with early and frequent need of treatment. At present, no chemotherapeutic regimens can be considered curative and all patients will die with (or because of) their disease. In recent years, research on CLL has led to important discoveries that help defining patients' prognosis at the moment of diagnosis. These prognostic factors, which are derived from the biological features of the leukemic lymphocytes, are now rapidly moved into the clinical arena. They are used to stratify patients in selected clinical trials to assess the value of early and more modern treatments, which are becoming available to hematologists.

Perspectives on familial chronic lymphocytic leukemia: genes and the environment

Chronic lymphocytic leukemia (CLL) comprises a substantial proportion of leukemias in adults in the western hemisphere. Male gender, increasing age, ethnicity (high in Caucasians, lowest in Asians), and family history are risk factors. Although no specific extrinsic etiologic factors have been established, farming and pesticide exposure are associated with increased risk. Migration studies confirm that ethnic groups retain the risk associated with their origin rather than their new location, favoring a role for heredity. Kindreds with multiple cases of CLL have been well described in the literature and studies in large populations confirm that lymphoproliferative malignancies and especially CLL occur together at a rate that cannot be attributed to chance. Since environmental factors cannot readily explain the familial aggregations, a hereditary factor that affects susceptibility to CLL is likely. The identification of clones that are immunophenotypically identical to CLL in healthy individuals from CLL kindreds (14% to 18%) as well as in the general population (3.5% in age bracket >65 years) suggests a possible precursor condition, but longitudinal studies will be necessary to establish significance in the general population. Family (linkage) and population (candidate gene) studies to date have been too small to identify the specific genes that account for increased susceptibility; larger studies including planned consortia to identify additional high-risk kindreds for genetic studies, as well as the application of advanced technologies such as genomics, cytogenetic, expression, and proteomics, are widely expected to advance understanding over the next few years.

The nature and origin of the B-chronic lymphocytic leukemia cell: a tentative model

Chronic lymphocytic leukemia cells have the profile of antigen (Ag) activated memory B cells but also show a constellation of T-cell-associated properties. We suggest that the early transforming events may occur in an early lymphoid progenitor. This precursor differentiates into a mature B cell that, though retaining T-cell features, has a functional B-cell receptor that may allow Ag intervention to trigger clonal expansion. This model has to cope with the existence of at least two subsets of the disease as defined by their IgVH genes mutational status. Mutated cases have a lower capacity to interact with Ag and are reminiscent of anergic cells. This explains their less harmful behavior as compared with unmutated case, which have a more aggressive potential likely because they had the opportunity to acquire additional chromosomal aberrations after repeated rounds of Ag stimulation and replication.

Familial B-Cell Chronic Lymphocytic Leukemia in a Population of Patients from Southern Italy

We investigated the prevalence of chronic lymphocytic leukemia (CLL) in 9650 relatives of 510 CLL patients from 5 different regions (Apulia, Basilicata, Campania, Calabria, and Sicily) of Southern Italy. Data collection included a family history questionnaire. In our series of 510 CLL patients, 53 families with 2 or more individuals who had chronic lymphoproliferative disease (CLD) or other hematological malignancies were identified. In these families, 27 cases of CLL, 10 of indolent non-Hodgkin's lymphoma, and 7 of multiple myeloma were identified in relatives of CLL probands. Twenty-two relatives developed hematological malignancies other than CLD (19, acute leukemia; 3, chronic myeloid leukemia). In this study the prevalence of CLD in relatives of 510 CLL patients was 8.6% (44/510), and the prevalence of CLL in the same series was 5.2% (27/ 510). Considering the presence of clusters of individuals with hematological malignancies, overall our series contained 4 families showing a cluster with more than 2 cases. The most frequent pattern of affected family members was represented by 39 families (39/53 [73%]) with affected siblings or cousins only. Twenty siblings had CLL. The other families showed a multigenerational pattern with an affected parent-offspring relationship in only 11 (21%) of the cases and with a combination of the first 2 categories in 3 (6%) of the families. In 8 families belonging to both the last 2 mentioned groups, the affected offspring had an earlier disease onset than their parents, suggesting anticipation. We estimated the size and examined the pattern of familial aggregation of hematological malignancies, in particular CLL/CLD, in a specific geographical area. CLL was the most frequent disease in relatives, mainly siblings, of our CLL patients. Our results may be a contribution to the characterization of the epidemiological distribution pattern of CLL.

Decreased chronic lymphocytic leukemia incidence in Asians in Los Angeles County

Chronic lymphocytic leukemia (CLL) is rare in Asians living in Asia and possibly in US Asians. In contrast, CLL is the most common leukemia in whites. The basis for this ethnic and geographic variation is unknown. We compared average annual age-adjusted incidence rates (AAIR) of CLL diagnosed from 1972 to 1995 among Los Angeles County-resident Asians, non-Spanish-surnamed- and Spanish-surnamed whites (non-Hispanic and Hispanic-whites) and blacks using the University Southern California-Cancer Surveillance Program (USC-CSP), the population-based cancer registry for Los Angeles County. Asian groups studied included Chinese, Japanese, Filipinos and Koreans. Expected numbers of CLL cases were based on the age-adjusted incidence rates in non-Hispanic whites and compared to numbers of cases observed in Chinese, Japanese and Filipinos. Possible association of socioeconomic state (SES) was assessed using AAIRs with SES-specific denominators. In the absence of denominators by birthplace, the association of birthplace and CLL-incidence was evaluated using proportional odds ratios (POR). Los Angeles County Asian males and females had significantly lower AAIRs than non-Hispanic whites (males: AAIR=0.7 per 100000 population, 95% confidence interval (CI), 0.5-1.0 vs. 4.4, 95% CI, 4.3-4.6; and females: AAIR=0.5, 95% CI, 0.3-0.7 vs. 2.3, 95% CI, 2.2-2.4). Fewer Japanese Chinese and Filipinos were diagnosed with CLL than expected (P<0.01). There was no association of birthplace (POR=0.9, 95% CI, 0. 5-1.9) or SES on CLL-risk. CLL-risk was markedly lower in Los Angeles County Asians compared to non-Hispanic whites. Neither birthplace nor socioeconomic state accounted for this difference suggesting a role for genetic or other environmental factors in decreasing CLL-risk.

Cytogenetic abnormalities in chronic B-cell lymphoproliferative disorders in Chinese patients

We analyzed the cytogenetic findings of 59 Chinese patients with chronic B-cell lymphoproliferative disorders. More than half of the patients (n = 36, 61%) had chronic lymphocytic leukemia. Cytogenetic abnormalities were demonstrated in 44.1% (26/59) of the patients. Trisomy 12 was the most frequent abnormality in chronic lymphocytic leukemia and was found in 27.8% (10/36) of the patients, indicating that the incidence of trisomy 12 in chronic lymphocytic leukemia in Chinese patients might not be low compared with the West as previously suggested. Structural abnormalities involving chromosomes 13 at band q14 were the next most common abnormalities in patients with chronic lymphocytic leukemia. Among the 11 patients with mantle cell lymphoma in leukemic phase, t(11;14) was seen in only 2 patients (18.2%). Several unusual cytogenetic abnormalities also were found.

The spectrum of chronic lymphoproliferative disorders in Chinese people. An analysis of 64 cases

BACKGROUND

Chronic lymphoproliferative disorders are considered rare in Oriental patients and are thought to constitute only 2% of all leukemias in these patients, compared to 20-30% in Western patients. We conducted a retrospective analysis of Chinese patients with chronic lymphoproliferative disorders to define the frequency and spectrum of these disorders.

METHODS

A consecutive series of Chinese patients with leukemia and lymphoproliferative disorders seen at two regional hospitals in Hong Kong were analyzed retrospectively. The diagnosis of chronic lymphoproliferative disorders was based on morphologic and immunologic criteria proposed by the French-American-British Cooperative Study Group.

RESULTS

Sixty-four Chinese patients with chronic lymphoproliferative disorders were identified, and these patients constituted 19% of a total of 342 cases of leukemia diagnosed in 3 years. Chronic lymphocytic leukemia was the most common form, occurring at a frequency of 12.5% of all leukemias. The clinicopathologic features of these patients were similar to those of Western patients, except that Chinese patients tended to present with more advanced (Rai's Stages III and IV; Binet's Stage C) and bulky (splenomegaly > 9 cm) disease, and expressed lambda light chain about six times more frequently. Other chronic lymphoproliferative disorders identified in this study included prolymphocytic leukemia, mantle zone lymphoma, hairy cell leukemia, splenic lymphoma with villous lymphocytes, large granular lymphocyte leukemia, and Sezary syndrome. The authors did not identify any case of human T-cell lymphotropic virus-I-related lymphoproliferative disorders within the study period.

CONCLUSION

In addition to providing the frequencies of various chronic lymphoproliferative disorders in southern Chinese people, this study also showed that these disorders no longer should be considered rare in this population. Inherent biologic differences between lymphoproliferative disorders in Chinese and Western patients also may exist.