Cytogenetics and Molecular Genetics

Hypercalcemia in childhood acute lymphoblastic leukemia: frequent implication of parathyroid hormone-related peptide and E2A-HLF from translocation 17;19

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Abstract

Hypercalcemia is relatively rare but clinically important complication in childhood leukemic patients. To clarify the clinical characteristics, mechanisms of hypercalcemia, response to management for hypercalcemia, incidence of t(17;19) and final outcome of childhood acute lymphoblastic leukemia (ALL) accompanied by hypercalcemia, clinical data of 22 cases of childhood ALL accompanied by hypercalcemia (>12 mg/dl) reported in Japan from 1990 to 2005 were retrospectively analyzed. Eleven patients were 10 years and older. Twenty patients had low white blood cell count (<20 × 109/l), 15 showed hemoglobin8 g/dl and 14 showed platelet count 100 × 109/l. Parathyroid hormone-related peptide (PTHrP)-mediated hypercalcemia was confirmed in 11 of the 16 patients in whom elevated-serum level or positive immunohistochemistry of PTHrP was observed. Hypercalcemia and accompanying renal insufficiency resolved quickly, particularly in patients treated with bisphosphonate. t(17;19) or add(19)(p13) was detected in five patients among 17 patients in whom karyotypic data were available, and the presence of E2A-HLF was confirmed in these five patients. All five patients with t(17;19)-ALL relapsed very early. Excluding the t(17;19)-ALL patients, the final outcome of ALL accompanied by hypercalcemia was similar to that of all childhood ALL patients, indicating that the development of hypercalcemia itself is not a poor prognostic factor.

Introduction

Hypercalcemia is a frequent complication in adults with malignancy, and its incidence has been estimated as 5–20%.1 In contrast, in the report from St Jude Children's Research Hospital, the incidence of hypercalcemia among children with malignancy who were treated from 1962 to 1991 was only 0.4%.2 Among the 25 affected children reported from St Jude Children's Research Hospital, 10 had ALL including six cases of B-precursor ALL and three cases of mature B-ALL, and 14 had solid tumors including four cases of rhabdomyosarcoma. Therefore, hypercalcemia develops most commonly in ALL among childhood malignancies. Despite the importance in clinical management, owing to its relative rarity, the clinical characteristics of childhood ALL accompanied by hypercalcemia, mechanisms of hypercalcemia, response to current management for hypercalcemia and final outcome of ALL accompanied by hypercalcemia remain totally unclarified. There are two main mechanisms of hypercalcemia in malignancy: localized bone destruction by invasive cancer cells with the participation of various cytokines, and osteoclastic bone resorption mediated by humoral tumor-derived factors.1, 3, 4 Hypercalcemia in malignancy is frequently mediated with parathyroid hormone-related peptide (PTHrP) by increasing osteoclastic bone resorption, renal resorption of calcium and renal phosphate loss.5, 6 Although several case reports showed the involvement of PTHrP in childhood ALL complicated with hypercalcemia,7, 8, 9 its significance remains to be confirmed in a larger study.

t(17;19)(q21-q22;p13), which generates E2A-HLF fusion transcription factor,10, 11 is a rare translocation present in less than 1% of childhood ALL cases,12 and its association with hypercalcemia, acquired coagulation abnormalities and extremely poor therapeutic outcome has been noticed.13, 14, 15, 16 The E2A-HLF fusion gene encodes a chimeric protein in which the transactivation domain of E2A links to the basic leucine zipper dimerization and DNA-binding domain of HLF.10, 11 E2A-HLF promotes anchorage-independent growth of murine fibroblasts17, 18 and protects cells from apoptosis owing to growth factor deprivation,19, 20, 21 and E2A-HLF transgenic mice develop T-lineage lymphoid malignancies.22, 23 Although their significance in the clinical features has been controversial, there are two types of fusion: type 1 is generated by the fusion between exon 13 of E2A and exon 4 of HLF with an insertion of cryptic exon (joining region) maintaining an open-reading frame, whereas type 2 is generated by the fusion between exon 12 of E2A and exon 4 of HLF in the same reading frame.24 Of note, despite its rarity, two of the six B-precursor ALL patients with hypercalcemia reported from St Jude Children's Research Hospital showed t(17;19) on cytogenetic analysis,2 and the two patients were confirmed to have E2A-HLF fusion.10 Although these observations suggest the frequent association of t(17;19) with the development of hypercalcemia in childhood ALL, more detailed analyses of additional cases are needed to adequately address this point.

In this study, we undertook a retrospective review of 22 patients with childhood ALL other than mature B-ALL, who developed hypercalcemia at onset or relapse of ALL. We found that childhood ALL accompanied by hypercalcemia was frequently associated with t(17;19) and E2A-HLF expression, and that PTHrP-mediated hypercalcemia was revealed in the half of the 22 patients and over two-thirds of the patients in whom conclusive data were available.

Materials and methods

Patients and diagnosis criteria for PTHrP-mediated hypercalcemia

Hypercalcemia was defined as total serum calcium concentration of greater than 12.0 mg/dl. From 1990 to 2005, 25 patients with childhood ALL with L1 and L2 subtypes in French–American–British (FAB) classification developed hypercalcemia during their clinical course and were reported at medical meetings (Japan Pediatric Society, Japanese Society of Pediatric Hematology, The Japanese Society of Hematology, and Japanese Society of Clinical Hematology) or in medical journals in Japan, where approximately 500 children are estimated to develop ALL per year. Three patients were excluded from the analysis owing to either loss of medical record or lack of response from the responsible physician, and as a result, 22 patients were enrolled in this study. The diagnosis of PTHrP-mediated hypercalcemia was made by the following criteria: (1) positive immunohistochemistry of PTHrP in leukemia cells, (2) elevated serum C-terminal PTHrP (C-PTHrP) level accompanying a low serum level of intact PTH (iPTH) (<10 pg/ml) owing to a negative feedback loop, (3) elevated serum C-PTHrP level accompanied by normal serum creatinine level. As the serum level of C-PTHrP, but not intact PTHrP (iPTHrP), was reported to be nonspecifically high in renal insufficiency,5 the diagnosis of PTHrP-mediated hypercalcemia was not concluded in the cases with elevated serum C-PTHrP level, in whom the serum creatinine level was elevated or not monitored and the iPTH level was not downregulated or not monitored. The upper limit of normal range for serum C-terminal PTHrP level varied from 40 to 61 pmol/l in each institute, and elevation of serum C-terminal PTHrP level was determined depending on each institutional normal range.

Reverse transcription (RT)-polymerase chain reaction (PCR) for E2A-HLF

RT-PCR analysis for E2A-HLF using patients' samples was approved by the institutional review board of the University of Yamanashi. Informed consent was obtained from the patients or the parents. Total RNA was isolated from bone marrow cells with Trizol (Life Technologies, Rockville, MD, USA) according to the manufacturer's instructions. RT was performed with 2 μg of total RNA, random hexamers and Superscript reverse transcriptase (Life Technologies) under conditions recommended by the manufacturer. PCR was performed using the following primers that were homologous to sequences in E2A exon 12 and exon 13, and HLF exon 4 (Figure 1a): E2A exon 12 (e12), 5′-IndexTermgacatgcacacgctgctgcc-3′; E2A exon 13 (e13), 5′-IndexTermgcctcatgcacaaccacgcg-3′; HLF exon 4 (e4), 5′-IndexTermcccggatggcgatctggttc-3′. Amplification was performed for 35 cycles at 94°C for 30 s, 56°C for 30 s and 72°C for 1 min. As a control, PCR for c-abl was performed under the same conditions using the following primers: c-abl sense, 5′-IndexTermgtatcatctgactttgagcc-3′; c-abl antisense, 5′-IndexTermgtaccaggagtgtttctcca-3′. The cell lines UOC-B1 and HAL-O1, which have type 1 fusion consisting of E2A exon 13 and HLF exon 4,24 and Endo-kun, which has type 2 fusion consisting of E2A exon 12 and HLF exon 424 and was established from case 1, were used as positive controls.

Figure 1
figure1

Representative analysis of RT-PCR amplification of E2A-HLF. (a) Schematic representation of two types of fusion. Type 1 is generated by fusion between exon 13 of E2A and exon 4 of HLF with an insertion of cryptic exon (joining region; JR) maintaining an open reading frame, whereas type 2 is generated by fusion between exon 12 of E2A and exon 4 of HLF in the same reading frame. The relative positions of the primers used to amplify the two types of E2A-HLF fusion complementary DNAs are shown. PCR using e13 and e4 primers is expected to generate a 179-bp + JR product from type 1 fusion but no product from type 2 fusion, whereas PCR using e12 and e4 primers generates a 180-bp product from type 2 fusion and 303-bp + JR product from type 1 fusion. (b) RT-PCR of E2A-HLF fusion. The left panel indicates the PCR products using e13 and e4 primers, and the right panel indicates the PCR products using e12 and e4 primers. Type 1 E2A-HLF was confirmed in Case 4 (lanes 4 and 10) as UOC-B1 (lane 5) and HAL-01 (lane 6), and type 2 E2A-HLF was confirmed in Case 5 (lanes 3 and 9) as Endo-kun (lane 11). None of the E2A-HLF transcripts was detectable in Case 15 (lanes 2 and 8). Lanes 1 and 7 demonstrate the molecular size marker. The RT-PCR product of c-abl was confirmed in each of the samples (data not shown).

Statistical analysis

All statistical analyses were performed with StatView (version 5.0.1) software. Event-free survival (EFS) was estimated according to Kaplan–Meier analysis. The starting point was the date of diagnosis of ALL, and the end point was relapse. Time was censored at last follow-up, and follow-up was updated in February 2006. Univariate comparison of EFS in different groups of patients was performed using the log-rank test, and χ2-test and Student's t-test were used to assess the association between different characteristics.

Results

Characteristics of leukemia

The main clinical features of the 22 patients with ALL who developed hypercalcemia are summarized in Table 1. Although observation period was not completely identical, their clinical features were compared with those of the childhood ALL patients in the Tokyo Children's Cancer Study Group (TCCSG) treated with L89-12 (1989–1992, 418 patients) and L92-13 (1992–1995, 347 patients) protocols (Table 2),25 in which approximately 20% of the patients in Japan were registered and Cases 3, 5 and 9 were enrolled. The incidence of age greater than 10 years at diagnosis of ALL in the present study (50%) was significantly higher (P=0.005) than that in the childhood ALL cases reported from TCCSG (23.8%). The male–female ratio was 54.5% and was identical to that in the childhood ALL cases reported from TCCSG (54.6%). Initial white blood cell count (WBC) of the cases with hypercalcemia ranged from 2 to 90 × 109/l (median, 6.2 × 109/l) and leukemic blasts were undetectable in the peripheral blood in eight patients. The rate of WBC<20 × 109/l (90.9%) was significantly higher (P=0.010) than the respective rate in childhood ALL reported from TCCSG (64.6%). The rates of severe anemia (hemoglobin<8 g/dl) (27.3%) and thrombocytopenia (platelet count<100 × 109/l) (36.4%) were significantly lower (P=0.025 and 0.004, respectively) than those in childhood ALL in the TCCSG (51.1 and 66.1%, respectively). Intravenous coagulopathy was noticed in five of 20 patients. All of the patients except for Case 20 with dry tap marrow showed B-precursor immunophenotype. No patient showed T-cell immunophenotype. The incidence of T-cell immunophenotype (0%) tended to be low (P=0.098) compared with that in childhood ALL reported from the TCCSG (11.6%). Negative to low expression of CD19 (< 30%) was noted in two patients (Cases 19 and 21), and expression of CD13 and CD33 (10%) was confirmed in 6 (Cases 1, 2, 5, 6, 10 and 22) and eight patients (Cases 1, 2, 3, 4, 5, 9, 18 and 22), respectively.

Table 1 Clinical and laboratory characteristics of the patients with ALL with hypercalcemia
Table 2 Comparison of characteristics of patients in present study and patients with childhood ALL in the TCCSG

Incidence of t(17;19)

On karyotypic analysis (Table 1), metaphase was not obtained in five patients, and normal karyotype was revealed in nine patients. Cases 1 and 4 harbored t(17;19)(q21;p13) and add(19)(p13) at disease onset, respectively. Cases 2, 3 and 5 who showed normal karyotype at onset, harbored t(17;19)(q21;p13) at relapse. RT-PCR analysis of E2A-HLF was performed in nine patients in whom frozen marrow samples were available (Table 1 and Figure 1). Type 1 E2A-HLF was detected in Cases 2 and 4, whereas type 2 E2A-HLF was detected in Cases 1, 3 and 5. In contrast, E2A-HLF transcripts were not detectable in Cases 7, 8, 15 and 18, who showed neither add(19)(p13) nor t(17;19)(q21;p13) in the cytogenetic study. Of note, all five patients with t(17;19)-ALL expressed CD33 (Table 1) and the incidence of CD33 expression among patients with t(17;19)-ALL was significantly higher than that among the other 16 patients (P=0.002 by χ2-test). Three patients with t(17;19)-ALL had L2 phenotype (Table 1) and the incidence of L2 phenotype among patients with t(17;19)-ALL was significantly higher than that among the other patients (P=0.008 by χ2-test). Four patients with t(17;19)-ALL developed the disease at age greater than 10 years, and two patients had coagulopathy.

Clinical characteristics of hypercalcemia

Hypercalcemia was present at the time of original diagnosis in 18 patients and at disease recurrence in four patients (Cases 1, 2, 5 and 7), and a diagnosis of hypercalcemia was made before treatment. Table 3 summarizes the clinical symptoms and laboratory data at diagnosis except for serum levels of blood–urea–nitrogen and creatinine, which were shown as the highest values before resolution of hypercalcemia. The total serum calcium concentration was 15 mg/dl or greater in 16 patients (72.7%). At least one clinical symptom associated with hypercalcemia was observed in all patients and the incidence of each symptom was as follows: emesis in 11 patients (50%), bone pain in 13 patients (59.1%), osteolytic lesion in 14 patients (63.6%), fracture of the vertebral bone in four patients (18.2%), and renal insufficiency with elevated serum creatinine level to 1.0 mg/dl or higher in 14 (66.7%) of 21 patients. Elevated serum creatinine was associated with older children (10 years old) (P=0.0002 by χ2-test) and infrequently associated with hypophosphatemia (4 mg/dl) (P=0.02 by χ2-test).

Table 3 Clinical and laboratory characteristics of hypercalcemia complicated in the patients with ALL

Mechanisms of the development of hypercalcemia

The serum C-terminal PTHrP (C-PTHrP) level was elevated in 15 of the 16 patients assayed (Table 3). The diagnosis of PTHrP-mediated hypercalcemia was made by positive immunohistochemistry of PTHrP in leukemia cells in the two patients assayed (Cases 6 and 7). The seven patients with an elevated serum C-PTHrP level (Cases 1, 2, 3, 8, 9, 10 and 11) accompanying a low serum level of iPTH owing to a negative feedback loop were diagnosed to have typical PTHrP-mediated hypercalcemia. Cases 12 and 13 with elevated serum C-PTHrP level accompanied by normal serum creatinine level were concluded to have PTHrP-mediated hypercalcemia. In contrast, Cases 4, 14, 15, 16 and 17 with elevated serum C-PTHrP level, in whom the serum creatinine level was elevated or missing and the iPTH level was not downregulated or missing, were not concluded to have PTHrP-mediated hypercalcemia. iPTHrP was undetectable in serum in all four patients assayed (Cases 18, 19, 20 and 21), indicating that the involvement of PTHrP in their hypercalcemia is excluded. Among these four patients, the serum phosphorus level was low and serum 1,25-(OH)2 vitamin D (calcitriol) level was normal in the three patients assayed, indicating that involvement of calcitriol-mediated hypercalcemia is unlikely because it is characterized by elevated calcitriol level accompanied by normal serum phosphorus level.4 In Case 22, iPTH was markedly elevated but C-PTHrP was normal in the serum, suggesting ectopic production of PTH by leukemia cells. Collectively, among the 21 patients whose PTHrP data were available, involvement of PTHrP-mediated hypercalcemia was confirmed in 11 patients (Cases 1, 2, 3, 6, 7, 8, 9, 10, 11, 12 and 13) but ruled out in five patients (Cases 18, 19, 20, 21 and 22). Of importance, hypercalcemia was definitely mediated by PTHrP in all three patients with t(17;19)-ALL in whom informative data were available (Cases 1, 2 and 3).

Management of hypercalcemia

Intravenous hydration with or without furosemide was administered to all patients. In Case 5, the hypercalcemia resolved without additional therapy. Fifteen patients received calcitonin (Cases 1, 2, 3, 4, 6, 7, 9, 10, 12, 13, 14, 16, 17, 18 and 22), 11 patients received bisphosphonate (Cases 2, 4, 6, 9, 10, 11, 15, 18, 19, 21 and 22), and seven of those patients received both calcitonin and bisphosphonate. Ten of the 12 patients who were diagnosed in or after 1997 received bisphosphonate, whereas only one of the 10 patients diagnosed before 1997 did so. Among the 17 patients who received chemotherapy before resolution of hypercalcemia (Cases 1, 2, 3, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20 and 22), chemotherapy was started by oral predonisolone (PSL) alone in seven patients (Cases 2, 9, 10, 11, 18, 19 and 22). Hypercalcemia and renal insufficiency ultimately resolved in all patients treated with or without bisphosphonate (Figure 2). As summarized in Table 4, although the levels of serum calcium before treatment and the incidences of concomitant use of chemotherapy and calcitonin were equivalent between the patients treated with and without bisphosphonate, rapid reduction of serum calcium level (<10 mg/dl within 4 days) was observed significantly more often in patients who were treated with bisphosphonate than in patients who were not treated with bisphosphonate. Consistently, the serum creatinine level tended to decrease more rapidly in patients who were treated with bisphosphonate compared with those who were not treated with bisphosphonate. The minimum serum calcium level of the patients treated with bisphosphonate was significantly lower than that of the patients treated without bisphosphonate, and hypocalcemia (<8 mg/dl) developed more frequently in the patients who were treated with bisphosphonate. Although no clinical symptoms owing to hypocalcemia were noted, five of 11 patients treated with bisphosphonate and none of those treated without bisphosphonate required calcium supplementation. During the therapies for hypercalcemia, precipitation of calcium phosphate in urine was noticed in Cases 9, 10 and 14, and renal calculus developed in Case 10.

Figure 2
figure2

Changes in serum calcium (Ca) and creatinine (Cr) levels. Changes in the serum Ca level of the eight patients who were not treated with bisphosphonate (a) and the 11 patients who were treated with bisphosphonate (b) and changes in the serum Cr level of the patients who were (closed symbols) or were not (open symbols) treated with bisphosphonate, whose maximum level of serum Cr exceeded 1 mg/dl (c). The day of administration of the first dose of bisphosphonate was defined as day 0.

Table 4 Comparison of clinical course of hypercalcemia between patients who were or were not treated with bisphosphonate

Treatment outcome of leukemia

All patients achieved complete remission (CR), but leukemia relapsed in 11 patients including Case 14 who developed AML at relapse (Table 1). The EFS rate at 5 years from diagnosis of ALL was estimated as 46.2±11.7%. Of note, all five patients with t(17;19)-ALL relapsed very early and their 5-year EFS rate (0%) was significantly lower (p<0.0001 in log-rank test) than that of the other 17 patients (59.7±13.4%). Among the 18 patients who developed hypercalcemia at disease onset (excluding Cases 1, 2, 5 and 7), the 5-year EFS rate of two patients with t(17;19)-ALL (0%) was still significantly lower (P<0.0001 in log-rank test) than that of the other 16 patients (63.5±13.7%). Thus, excluding the patients with t(17;19)-ALL, the 5-year EFS rate of ALL patients accompanied by hypercalcemia is almost similar to that of childhood ALL patients in the TCCSG treated with L89-12, L92-13,25 L95-14 (1995–1999; 596 patients), and L99-15 (1999–2003; 623 patients) protocols, in which the 5-year EFS rate was 67.8±2.3, 63.4±2.7, 76.0±1.9 and 76.4±2.5%, respectively.

Discussion

This is the first cohort study of hypercalcemia associated with childhood ALL, and we retrospectively analyzed 22 Japanese patients reported in the last 15 years. Despite several limitations in a retrospective study, the present study newly demonstrated some characteristics of childhood ALL accompanied by hypercalcemia. The incidence of onset at age 10 years and older among the patients with hypercalcemia in the present study was significantly higher than that among all childhood ALL patients. Most of our patients had a low initial WBC and two-thirds of our patients had mild anemia and normal to mildly low platelet count, suggesting that symptoms associated with hypercalcemia rather than hematological abnormalities might lead to the diagnosis of leukemia in these patients. Importantly, we identified five patients with t(17;19)-ALL, and its incidence was estimated to be over 20%, indicating the frequent association of t(17;19) with the development of hypercalcemia in childhood ALL. In all of five t(17;19)-ALL patients in the present study, the leukemia relapsed very early. However, excluding the patients with t(17;19)-ALL, the 5-year EFS rate of ALL accompanied by hypercalcemia was almost similar to that of childhood ALL patients enrolled in TCCSG, indicating that the development of hypercalcemia itself is not a poor prognostic factor in childhood ALL. Thus, identification of t(17;19) is very critical to predict the prognosis of ALL with hypercalcemia.

Among the 21 patients whose PTHrP data were available, the involvement of PTHrP-mediated hypercalcemia was confirmed in 11 patients but ruled out in five patients, indicating that hypercalcemia in childhood ALL is most frequently mediated by PTHrP. The PTH and PTHrP genes are localized on 11p15.3–15.1 and 12p12.1–11.2, respectively, and none of the patients had detectable chromosomal abnormalities involving these regions in their cytogenetic analysis (Table 1), suggesting that amplification of the regions encoding the PTH and PTHrP genes might be unlikely as a mechanism for hypercalcemia. Of note, we confirmed the contribution of PTHrP in all three patients with t(17;19)-ALL in whom informative data were available, suggesting that E2A-HLF might induce the production of PTHrP as one of the downstream targets. PTHrP is a potent humoral factor of hypercalcemia, but it was reported that asymptomatic carriers of human T-cell leukemia virus-1 have an elevated serum level of PTHrP without hypercalcemia,26 suggesting that elevated PTHrP alone might not induce hypercalcemia. We previously reported that E2A-HLF induced the expression of SRPUL, which may play a role in bone invasion as an adhesion molecule.27 Therefore, frequent association of t(17;19)-ALL with hypercalcemia might result from a synergistic action of PTHrP and SRPUL as downstream targets of E2A-HLF. In contrast, the involvement of PTHrP was specifically ruled out in five patients. Among these five patients, the involvement of PTH in hypercalcemia was strongly suggested in one patient (Case 22) but not in the other four patients (Cases 18–21). Moreover, calcitriol-mediated hypercalcemia, the most frequent cause of hypercalcemia in lymphoma,4 was unlikely in these four patients. Of note, two patients (Cases 19 and 21) had B-precursor ALL with negative- or low-level expression of CD19 and their serum levels of tumor necrosis factor-α and interleukin-6, which are known to promote osteoclastic bone resorption and involve in hypercalcemia in malignancies,28, 29 were elevated at the onset of hypercalcemia,30 representing an independent subgroup of ALL with PTHrP-independent hypercalcemia.

In the present study, for the treatment of hypercalcemia, 17 patients received chemotherapy before complete resolution of hypercalcemia, and seven of them received PSL alone. Fifteen patients received calcitonin, 11 patients received bisphosphonates and seven of them received both. Bisphosphonates have been reported to be highly effective for the treatment of hypercalcemia complicated in malignancies with long duration of action by reducing osteoclast viability and inhibiting osteoclast-mediated resorption of bone.3, 31, 32, 33 As a first cohort study, we retrospectively confirmed that hypercalcemia resolved quickly in the patients treated with bisphosphonate compared with the patients who were not treated with bisphosphonate. Most of the patients treated with bisphosphonate developed hypocalcemia and almost the half of them required calcium supplementation. Elevated serum creatinine level was observed in two-thirds of our patients, particularly among patients with older age of onset, but was less common among patients with hypophosphatemia. Of importance, treatment of hypercalcemia resolved renal insufficiency and chemotherapy could be started safely. In particular, renal insufficiency rapidly resolved in patients who were treated with bisphosphonate. However, as there was no difference in the final outcome of survival or renal insufficiency between the patients treated with and without bisphosphonate, the usefulness of bisphosphonate in treating hypercalcemia that develops in ALL patients must be confirmed in a future large prospective study.

Table 5 summarizes the characteristics of 12 previously reported cases of t(17;19)-ALL9, 10, 11, 14, 15, 16, 34, 35 in addition to five cases identified in the present study. Hypercalcemia developed in 10 of 14 cases: four patients at their original diagnosis and six patients at disease recurrence. There was no association between hypercalcemia and the type of E2A-HLF fusion. Twelve of 15 t(17;19)-ALL patients were older than 10 years and eight of 16 patients had accompanying coagulopathy, which is a relatively rare complication in childhood ALL.13, 24 Although no available data in the previously reported cases, it should be noted that all t(17;19)-ALL cases in the present study expressed CD33 and three cases had L2 phenotype. Accordingly, older age of onset, coagulopathy, CD33 expression and L2 phenotype in FAB classification in childhood ALL accompanied by hypercalcemia strongly suggest t(17;19)-ALL. In addition to five patients in the present study, almost all of the patients with t(17;19)-ALL relapsed very early. The prognosis of leukemia in the patients who did not develop hypercalcemia (cases 4, 9, 11 and 12 in Table 5) was as poor as that in the patients who developed hypercalcemia at disease onset (cases 1, 5, 15 and 16 in Table 5), indicating that hypercalcemia did not affect prognosis of the patients with t(17;19)-ALL. Of note, one previously reported patient (Case 4 in Table 5) who exceptionally underwent allogeneic bone marrow transplantation (allo-BMT) in the first CR (13 weeks after diagnosis) maintained CR for 42 months,14 suggesting that allo-BMT performed early in the first CR might prolong the disease-free survival of t(17;19)-ALL patients even if not cured.

Table 5 Characteristics of t(17;19)-ALL

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Acknowledgements

We thank Masahiro Tsuchida (Department of Pediatrics, Ibaraki Children's Hospital, Mito, Japan) for providing the clinical data of TCCSG and Keiko Kagami (Department of Pediatrics, University of Yamanashi, School of Medicine) for technical supports.

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Correspondence to T Inukai.

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Inukai, T., Hirose, K., Inaba, T. et al. Hypercalcemia in childhood acute lymphoblastic leukemia: frequent implication of parathyroid hormone-related peptide and E2A-HLF from translocation 17;19. Leukemia 21, 288–296 (2007) doi:10.1038/sj.leu.2404496

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Keywords

  • hypercalcemia
  • childhood ALL
  • PTHrP
  • E2A-HLF
  • bisphosphonate

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