thioguanine-anhydrous and Precursor-B-Cell-Lymphoblastic-Leukemia-Lymphoma

Myelotoxicity during thiopurine therapy is enhanced in patients, who because of single nucleotide polymorphisms have decreased activity of the enzyme thiopurine methyltransferase (TPMT) and thus more thiopurine converted into 6-thioguanine nucleotides. Of 601 children with acute lymphoblastic leukemia (ALL) who were treated by the NOPHO ALL-92 protocol, 117 had TPMT genotype determined, whereas for 484 patients only erythrocyte TPMT activity was available. The latter were classified as heterozygous, if TPMT activity was <14 IU/ml, or deficient (<1.0 IU/ml). 526 patients had TPMT wild type, 73 were presumed heterozygous, and two were TPMT deficient. Risk of relapse was higher for the 526 TPMT wild type patients than for the remaining 75 patients (18 vs 7%, P=0.03). In Cox multivariate regression analysis, sex (male worse; P=0.06), age (higher age worse, P=0.02), and TPMT activity (wild type worse; P=0.02) were related to risk of relapse. Despite a lower probability of relapse, patients in the low TPMT activity group did not have superior survival (P=0.82), possibly because of an excess of secondary cancers among these 75 patients (P=0.07). These data suggest that children with ALL and TPMT wild type might have their cure rate improved, if the pharmacokinetics/-dynamics of TPMT low-activity patients could be mimicked without a concurrent excessive risk of second cancers.

Topics: Antimetabolites, Antineoplastic; Antineoplastic Combined Chemotherapy Protocols; Biotransformation; Child; Child, Preschool; DNA Damage; Female; Genotype; Humans; Inactivation, Metabolic; Infant; Male; Mercaptopurine; Methylation; Methyltransferases; Neoplasm Proteins; Neoplasms, Second Primary; Polymorphism, Genetic; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma; Precursor T-Cell Lymphoblastic Leukemia-Lymphoma; Recurrence; Risk; Scandinavian and Nordic Countries; Thioguanine

Both tumour suppressor and oncogenic functions have been ascribed to the atypical zeta isoform of protein kinase C (PKCζ), whereas its constitutively active form PKMζ is almost exclusively expressed in the brain where it has a role in long-term memory. Using primers unique for either isoform, we found that both PKCζ and PKMζ were expressed in a subset of paediatric acute lymphoblastic leukaemia (ALL) cases carrying a TCF3 (E2A) chromosomal rearrangement. Combined PKCζ and PKMζ (PKC/Mζ) protein as well as phosphorylation levels were elevated in ALL cases, especially TCF3-rearranged precursor B-ALL cases, compared with normal bone marrow (P<0.01). Furthermore, high PKC/Mζ expression in primary ALL cells was associated with increased sensitivity to 6-thioguanine and 6-mercaptopurine (P<0.01), thiopurines used in ALL treatment. PKCζ is believed to stabilize mismatch-repair protein MSH2, facilitating thiopurine responsiveness in T-ALL. However, PKC/Mζ knockdown in a TCF3-rearranged cell line model decreased MSH2 expression but did not induce thiopurine resistance, indicative that the link between high PKC/Mζ levels and thiopurine sensitivity in paediatric precursor B-ALL is not directly causal. Collectively, our data indicate that thiopurine treatment may be effective, especially in paediatric TCF3-rearranged ALL and other patients with a high expression of PKC/Mζ.

Topics: Basic Helix-Loop-Helix Transcription Factors; Cell Line, Tumor; Gene Expression Profiling; Gene Expression Regulation, Leukemic; HEK293 Cells; Humans; Isoenzymes; Lentivirus; Leukocytes, Mononuclear; Mercaptopurine; Phosphorylation; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Protein Kinase C; Thioguanine

The difference in the current cure rates between adult and childhood acute lymphoblastic leukaemia (ALL) may be caused by differences in drug resistance. Earlier studies showed that in vitro cellular drug resistance is a strong independent adverse risk factor in childhood ALL. Knowledge about cellular drug resistance in adult ALL is still limited. The present study compared the in vitro drug resistance profiles of 23 adult ALL patients with that of 395 childhood ALL patients. The lymphoblasts were tested by the MTT assay. The group of adult ALL samples was significantly more resistant to cytosine arabinoside, L-asparaginase, daunorubicin, dexamethasone and prednisolone. The resistance ratio (RR) was highest for prednisolone (31.7-fold) followed by dexamethasone (6.9-fold), L-asparaginase (6. 1-fold), cytosine arabinoside (2.9-fold), daunorubicin (2.5-fold) and vincristine (2.2-fold). Lymphoblasts from adult patients were not more resistant to mercaptopurine, thioguanine, 4-HOO-ifosfamide, mitoxantrone and teniposide. There were no significant differences in drug resistance between adult T-cell (T-) ALL (n = 11) and adult common/pre-B-cell (B-) ALL (n = 10). Additionally, adult T-ALL did not differ from childhood T-ALL (n = 69). There were significant differences between adult common/pre-B-ALL and childhood common/pre-B-ALL (n = 310) for prednisolone (RR = 302, P = 0.008), dexamethasone (RR = 20.9, P = 0.017) and daunorubicin (RR = 2.7, P = 0.009). Lymphoblasts from adults proved to be relatively resistant to drugs commonly used in therapy. This might contribute to the difference in outcome between children and adults with ALL.

Topics: Adolescent; Adult; Age Factors; Antineoplastic Agents; Asparaginase; Bone Marrow Cells; Child; Child, Preschool; Cytarabine; Daunorubicin; Dexamethasone; Doxorubicin; Drug Resistance, Neoplasm; Etoposide; Female; Humans; Idarubicin; Ifosfamide; Infant; Leukemia, Prolymphocytic; Leukemia, T-Cell; Male; Mercaptopurine; Middle Aged; Mitoxantrone; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Prednisolone; Prognosis; Statistics, Nonparametric; Teniposide; Thioguanine; Vincristine

Many reports have described the relationship of adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) activities with the immunological subclasses of acute lymphoblastic leukemia (ALL). The clinical significance of these enzymes in leukemias is not yet completely understood. We performed a study in 83 children with untreated ALL to establish the relationships of ADA and PNP to clinical outcome, in vitro drug resistance and differentiation stage of B-cell lineage ALL. ADA and PNP activities were determined radiochemically. In vitro resistance to 6-thioguanine (6-TG) was determined with the MTT assay. ADA activity was not different between proB- and cALL cases but decreased in the sequential differentiation stages cALL----preB-ALL----B-ALL. The PNP level was not different between the four stages of B-lineage ALL. Patients with cALL/preB ALL with low ADA activities had a significantly poorer probability of survival (p = 0.005) than patients with high ADA levels. Patients with cALL/preB ALL with low PNP activities showed a non-significant trend for a poorer prognosis (0.05 less than p less than 0.10) than patients with a high PNP level. Low ADA and PNP activities were not related to in vitro resistance to 6-TG. We conclude that ADA decreases and PNP remains constant in sequential differentiation stages of B-lineage ALL. Patients with precursor B-lineage ALL with low activities of ADA have a poorer prognosis than those with high activities of these enzymes. No relationship could be detected between ADA or PNP activity and resistance to 6-TG.

Topics: Adenosine Deaminase; Blood Cells; Bone Marrow; Cell Differentiation; Child; Drug Resistance; Humans; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Prognosis; Purine-Nucleoside Phosphorylase; Thioguanine; Tumor Cells, Cultured

Topics: Antimetabolites, Antineoplastic; Cell Division; Cell Line; Cell Survival; Drug Screening Assays, Antitumor; Humans; Isoxazoles; Leukemia-Lymphoma, Adult T-Cell; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma; Thioguanine