Cooperation of MLL/AF10(OM-LZ) with PTPN11 activating mutation induced monocytic leukemia with a shorter latency in a mouse bone marrow transplantation model.

PTPN11 mutation, a RAS signaling pathway mutation, is associated with MLL translocations in acute leukemia. A girl with MLL/AF10 AML was found to carry PTPN11G503A . To study the impact of PTPN11G503A cooperating with MLL/AF10 on leukemogenesis, we established a retroviral transduction/transplantation mouse model. Compared to the MLL/AF10(OM-LZ) leukemia cells harboring PTPN11wt , the cells harboring PTPN11G503A were hypersensitive to GM-CSF and IL3, and more resistant to death upon treatment with daunorubicin but sensitive to cytarabine. The cells harboring PTPN11G503A autonomously differentiated into macrophages (1.8%) in the medium containing IL3. Further studies showed that the cells had an elevated (∼2.9-fold) Csf1 transcription level and secreted more (∼4.5-fold) M-CSF to the medium which can stimulate monocyte/macrophage differentiation of BM cells. Mice transplanted with the cells harboring PTPN11G503A had a higher concentration of M-CSF in plasma. When mixed with the MLL/AF10(OM-LZ) leukemia cells harboring PTPN11wt , the cells harboring PTPN11G503A had an increased competitive engraftment and clonal expansion in the BM and spleen of recipient mice, although no competitive growth advantage was observed in the in vitro co-culturing assays. The mice transplanted with the MLL/AF10(OM-LZ) cells harboring PTPN11wt developed myelomonocytic leukemia, while those transplanted with the cells harboring PTPN11G503A -induced monocytic leukemia in a shorter latency. Our results demonstrated that addition of PTPN11G503A to MLL/AF10 affected cell proliferation, chemo-resistance, differentiation, in vivo BM recruitment/clonal expansion and accelerated disease progression.

Secondary acute monocytic leukemia positive for 11q23 rearrangement in Nijmegen breakage syndrome.

Nijmegen breakage syndrome (NBS) is an autosomal recessive chromosomal instability disorder characterized by a high incidence of pediatric hematologic malignancies. Majority of patients affected are of Slavic origin and share the same founder mutation of 657del5 within the NBN gene encoding protein involved in DNA double-strand breaks (DSB) repair. We report a case of a pediatric patient with NBS, who developed t(9;11)/AF9-MLL-positive AML as a second malignancy after successful treatment of T-NHL. The coexistence of NBN and MLL mutations suggests that the profound dysfunction of NBN may promote alterations of MLL that is mediated by error-prone non-homologous end joining pathway particularly in patients treated with DNA topoisomerase II inhibitors.

[Acute monoblastic leukemia with MLL/AF9 rearrangement which developed 18 months after myeloid sarcoma onset].

We describe a 36-month-old boy with acute monoblastic leukemia (AMoL M5a) and mixed-lineage leukemia (MLL)-AF9 rearrangement. At 18 months of age, he presented with swelling on the back of his hand that was considered to be an inflammatory change, but no hematological abnormalities were found. However, blasts with MLL-AF9 rearrangement were detected in biopsied tissue taken at the time and in peripheral blood samples taken 18 months later. These findings indicate that myeloid sarcoma with MLL-AF9 rearrangement may ultimately, though slowly, progress to AMoL.

The structure of the Klf4 DNA-binding domain links to self-renewal and macrophage differentiation.

Krueppel-like factor 4 (Klf4) belongs to the Sp/Klf family of zinc-finger transcription factors and is indispensable for terminal maturation of epithelial tissues. Furthermore, it is part of a small set of proteins that are used to generate pluripotent embryonic stem cells from differentiated tissues. Herein, we describe that a Klf4 zinc-finger domain mutant induces self-renewal and block of maturation, while wild-type Klf4 induces terminal macrophage differentiation. Moreover, we present the crystal structure of the zinc-finger domain of Klf4 bound to its target DNA, revealing that primarily the two C-terminal zinc-finger motifs are required for site specificity. Lack of those two zinc fingers leads to deficiency of Klf4 to induce macrophage differentiation. The first zinc finger, on the other hand, inhibits the otherwise cryptic self-renewal and block of differentiation activity of Klf4. Our data show that impairing the DNA binding could potentially contribute to a monocytic leukemia.

Hemophagocytic lymphohistiocytosis with MUNC13-4 gene mutation or reduced natural killer cell function prior to onset of childhood leukemia.

Hemophagocytic lymphohistiocytosis (HLH) is a rare histiocytic reactive process due to mutations in the perforin, MUNC13-4 or syntaxin 11 genes, or secondary to malignancy, infection or autoimmune disorder. HLH as a preceding diagnosis to leukemia is rare. We report two cases with progression to acute leukemia, one heterozygous for MUNC13-4 and the other with reduced natural killer (NK) cell function and perforin expression. These defects may predispose to a secondary HLH-like presentation of pre-clinical leukemia or confer increased susceptibility to malignancy. HLH patients with genetic mutations or NK cell function abnormalities need monitoring for future malignancy even if the HLH resolves.

[Acute monoblastic leukemia following granular lymphocyte proliferative disorder].

Granular lymphocyte proliferative disorder (GLPD) is often concomitant with a malignant tumor. We report a patient who developed acute monoblastic leukemia (AMoL) following GLPD. An 82-year-old Japanese man was admitted to our hospital for anemia in December 2006. The patient was diagnosed as having GLPD. In May 2007, the lymphadenopathy developed and the blasts in peripheral blood started to increase. The monoclonal rearrangement of T-cell receptor genes was not detected on Southern blot analysis. Surface marker analysis revealed that the blasts were positive for CD13 and CD64. The level of lysozyme in serum and urine were increased. Based on these findings, he was diagnosed with AMoL. The immunohistochemistry of the bone marrow clot specimen in the diagnosis of GLPD revealed the concomitant presence of a few small clusters of CD34+ cells. This finding suggests that the granular lymphocytes responded to the early stage of AMoL. We should monitor carefully the development of acute myeloid leukemia in newly diagnosed GLPD patients.

Estimating the risk of developing secondary hematologic malignancies in patients with T1/T2 prostate cancer undergoing diverse treatment modalities: A large population-based study.

BACKGROUND: Patients with prostate cancer (PC) are at a high risk of developing secondary hematologic malignancies (SHMs) after radiation therapy (RT), while no study has assessed the relationship of different treatment modalities with the occurrence of SHMs after PC at early stage. This study aimed to investigate the risks of developing SHMs in patients with T1/T2 PC undergoing different treatment modalities. METHODS: Patients with T1/T2 PC were identified from the Surveillance, Epidemiology, and End Results database. Competing risk regression (CRR) model was performed to evaluate the hazard ratios (HRs) of developing SHMs. As SHMs scarcely occur, the relative risk (RR) analysis was employed to compare the risks of different treatment modalities associating with the development of SHMs. RESULTS: The CRR analysis showed that undergoing RT was associated with a higher risk of developing SHMs (external beam radiation therapy [EBRT]: HR = 1.21, 95% confidence interval [CI]: 1.10-1.34; radioactive implant [RI]: HR = 1.20, 95% CI: 1.06-1.36). As for different types of SHMs, EBRT, and RI were correlated with decreased risks of developing CLL (RR = 0.67, 0.72; 95% CI: 0.53-0.85, 0.54-0.96, respectively), but with the increased risks of developing NHL (RR = 1.18, 1.23; 95% CI: 1.02-1.35, 1.05-1.44, respectively); EBRT also showed increased risks of developing acute/ chronic myeloid leukemia (AML/CML, RR = 1.54, 1.56; 95% CI: 1.16-2.03,1.05-2.33, respectively); No increased risk of developing SHMs was detected in patients who only underwent prostatectomy. CONCLUSIONS: Although RT was found to be associated with the increased risks of developing SHMs in patients with T1/T2 PC, this finding cannot be extended to diverse types of SHMs. RT was correlated with the increased risks of the development of NHL, AML, and CML, but with the decreased risk of developing CLL. Prostatectomy did not increase the risk of developing SHMs.

Secondary Acute Leukemia in Sarcoma Patients: A Population-Based Study.

PURPOSE: To compare rates of secondary acute leukemia between sarcoma patients and the general population, using data from the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) registry, and to examine whether various patient, tumor, and treatment factors were associated with development of a secondary acute leukemia. METHODS AND MATERIALS: Patients with a primary diagnosis of connective tissue malignancy between 1973 and 2008 in the SEER database were included. Multivariable competing risk analysis was used to determine risk factors associated with subsequent development of acute leukemia. Using observed-to-expected ratios, we compared incidence rates of secondary acute leukemia between sarcoma patients and the general population. RESULTS: A total of 72,945 patients were identified, with median follow-up of 131 months. On multivariable competing risk analysis, factors associated with increased risk of secondary acute leukemia included receipt of radiation therapy (hazard ratio [HR] 1.67, P=.02), distant disease (HR 2.67, P=.004), male gender (HR 1.53, P=.03), year of diagnosis (HR 0.98, P=.049), and Ewing sarcoma histology (HR 9.95, P < .0001) and osteosarcoma histology (HR 5.06, P=.0001). The observed-to-expected ratio for development of a secondary acute leukemia was 3.67 (95% confidence interval [CI] 1.95-6.28), 3.41 (95% CI 2.73-4.20), and 1.6 (95% CI 1.38-8.19) for acute lymphocytic leukemia, acute myeloid leukemia, and acute monocytic leukemia, respectively. The 10-year cumulative incidence of secondary acute leukemia for patients who did and did receive radiation therapy was 0.3% versus 0.1% (P=.02). CONCLUSIONS: Patients treated for sarcoma, in particular those with Ewing sarcoma and osteosarcoma histology, seem to have a higher incidence of secondary acute leukemia as compared with the general population. Treatment factors including radiation therapy and chemotherapy seem to play a role in this increased risk, although the absolute incidence nevertheless remains very small.

Myelodysplastic syndrome with transformation to acute monocytic leukemia with FLT3-ITD mutation following orthotopic liver transplantation.

A rare case of a 46-year-old man who underwent myelodysplastic syndrome, acute monocytic leukemia with FLT3-ITD mutation and splenic disruption following orthotopic liver transplantation is reported. The study of this case may be helpful to understand both the pathogenesis of acute leukemia and new complication of liver transplantation.

Leukemogenicity of v-myb-transformed monoblasts cells can be modulated by normal bone marrow environment.

The avian myeloblastosis virus (AMV) causes monoblastic leukemia in the chick. Two non-producer clones of AMV-transformed monoblasts, BM2/C3A and BM2L/A2B5, have been described (see Bottazzi et al., this issue). They differ in their growth requirements and in their ability to induce leukemia when injected into the chick embryo. We first genetically tagged these clones by retroviral infection with a vector expressing the bacterial lacZ gene. Then, we injected the lacZ-positive cells via the chorioallantoic vein into chick embryos. With BM2L/A2B5 cells, the bone marrow of the injected birds was rapidly invaded by lacZ-positive cells. In addition, these cells rapidly overgrew cultures of bone marrow cells derived from injected animals. Conversely, the growth of BM2/C3A was inhibited in the injected animals and only a few blue cells, with the morphology of macrophages, were detected in cultures of bone marrow cells. We developed an in vitro assay to mimic in vitro the differential growth of BM2/C3A and BM2L/A2B5 observed in vivo. These data strongly suggest that BM2/C3A cells retain their ability to differentiate into macrophages in the normal bone marrow environment and that BM2L/A2B5 cells differ from BMC/C3A in the loss of this capacity.

BM2L is a spontaneous leukemogenic variant of a non-leukemogenic v-myb-transformed myeloid cell line.

Leukemogenesis is a complex process involving an accumulation of genetic lesions affecting both growth and differentiation in cells of the hematopoietic lineage. Our laboratory has established a non-producer v-myb-transformed cell line (BM2/C3A) which, when injected into the chicken embryo, does not produce leukemia. Recently, a spontaneous variant of this cell line, called BM2L, was obtained from in vivo experiments. BM2L produces an acute monoblastic leukemia when injected into the chicken embryo. BM2L cells do not differentiate in vivo or in vitro, but continue to proliferate under conditions in culture that allow for the differentiation of BM2/C3A cells into macrophages. In addition, BM2L cells have reduced requirements for exogenous growth factors. BM2L cells contain the v-myb allele and express v-Myb protein, but leukemogenicity does not involve point mutations in v-myb. The BM2 model, consisting of two non-producer cell lines differing in vivo in their leukemogenicity, provides a novel system for identifying genes that play a role in the induction or suppression of leukemogenesis.

Efficacy trial of pipobroman in polycythemia vera and incidence of acute leukemia.

A trial was conducted between 1970 and 1981 with pipobroman (PB) in 100 consecutive patients with polycythemia vera (PV), followed for a median time of 60 months, to evaluate the efficacy of this drug and assess the risk of acute leukemia. Phlebotomy was not done before PB was given. Hematologic remission was achieved in 92% of previously untreated patients in a median time of 12 weeks (range, 6-48 weeks) and maintained for a median of 48 months. Acute hematologic toxicity was absent. The median overall survival was 140 months with 65% five-year complication-free survival; the overall death rate at 12 years was 23% (6% of patients died of thrombotic complications). The actuarial risk of acute leukemia was 6% and 9% at five and seven years, and the time from the diagnosis of PV to leukemia ranged from 14 to 81 months. Myelofibrosis occurred in three patients and lung carcinoma in one. All leukemias were nonlymphoid with prominent monocytic component and dyserythropoiesis. One patient had erythroleukemia, two cases were heralded by preleukemia with chromosomal abnormalities, one involving the chromosomes 5 and 7. PB is effective in PV; however, despite an easy induction of remission, continuous low-dose maintenance is necessary and the risk of subsequent acute leukemia is still significant.

Leukemia following treatment of germ cell tumors in men.

We investigated the incidence of leukemia occurring subsequent to the treatment of germ cell tumors in men at our institution over a 30-year interval and found four patients with acute nonlymphocytic leukemia (ANLL) and one patient with chronic myelomonocytic leukemia. The relative risk (observed/expected cases) estimates for the development of leukemia ranged from 13.7 (P = .0005) in the total population to 50.1 (P = .0001) in the group treated with cytotoxic agents alone. All three patients with ANLL treated with contemporary antileukemic therapy had complete responses, with survivals of 7, 29, and 133 + months. In a review of the literature, 14 additional cases of germ cell tumors were found in which the men subsequently developed leukemia. It is concluded that leukemia following germ cell tumors is increased in incidence and is likely to be treatment induced. Complete responses and long-term survival are possible in secondary leukemia and aggressive antileukemic therapy should be given.

Relapse as acute monoblastic leukemia (AML-M5) of t(6;9) acute myeloblastic leukemia (AML-M2).

Two patients with acute myeloblastic leukemia with t(6;9)(p23;q34) translocation and classified as AML-M2 relapsed as acute monocytic leukemia (AML-M5). Trisomy 8 was found associated with t(6;9) at that time in both patients. Such changes in differentiation of leukemic cells have not previously been reported in this subtype of AML and add data favoring the pluripotent nature of the stem cell involved in leukemia with t(6;9).

Donor leukemia following allogeneic bone marrow transplantation.

Although allogeneic bone marrow transplantation has been shown to be a highly effective treatment for acute and chronic leukemia, leukemic relapse remains a significant problem. Leukemic relapse occurs in recipient cells in the majority of cases, but the paucity of donor cell leukemias may reflect the sensitivity of the investigative technique. We have developed a highly sensitive technique to identify the origin of all hematopoietic cells in the post transplant state which is based on PCR amplification of microsatellites, polymorphic tandem repetitive elements. We have identified donor leukemia (AML M5) following a sex matched BMT for severe aplastic anemia, verified a previously reported case of donor leukemia following BMT for chronic granulocytic leukemia and recently identified an acquired cytogenetic abnormality(del 11q23) in donor cells four years following an apparently successful BMT for AML. In all cases the donors have remained healthy. Postulated mechanisms include transfer to the transplanted marrow of a dormant oncogene residing in the DNA of either a virus, the chromosomes of degenerating irradiation damaged host leukemic cells or in the marrow stroma which is radioresistant and host in origin following BMT. Using sensitive techniques donor leukemia has been shown to be a more common event than was previously thought and an understanding of its pathogenesis may allow us to elucidate leukemogenic mechanisms in man.