ASSESSMENT OF GH-IGF1 AXIS AND TO STUDY RESPONSE TO GH THERAPY IN CHILDREN WITH CML IN REMISSION HAVING GH DEFICIENCY

CML is a myeloproliferative disorder defined by the presence of the Philadelphia chromosome, which arises from the reciprocal translocation of genes on chromosomes 9 and 22.It is rare in childhood and accounts for 2-3% of all leukemias in childhood.

BCR-ABL gene on Philadelphia chromosome results in a 210kd fused BCR-ABL protein with constitutive tyrosine kinase activity, and subsequent activation of cytoplasmic and nuclear signal transduction pathways including STAT, RAS, JUN, MYC, and phosphatidylinositol-3 kinase. The ultimate result of such activation is the myeloid proliferation and differentiation and suppressed apoptosis.

Children present with a higher WBC count, otherwise presentation is nearly identical to adults. Current treatment include tyrosine kinase inhibitors (TKI) and allogeneic stem cell transplant (SCT).Imatinibmesylate inhibits the tyrosine kinase (TK) activity of BCR-ABL1 and several related TKs, including c-kit and the platelet-derived growth factor receptor (PDGFR). Development of tyrosine kinase inhibitor (TKI) therapy has revolutionizedtreatment of CML. Imatinib or second generation TKIs (dasatinib or nilotinib) have become standard front-line therapy forchildren and adults with CML and are also important componentsof therapy for Ph+ acute lymphoblastic leukemia (ALL).

TKIs are administered orally and cause a number of side effects including fatigue, hypertension, rash, impaired wound healing, myelosuppression, and diarrhea . The overall toxicity of TKIs, while less life-threatening than conventional cytotoxic chemotherapy, nevertheless is common, and may require dose reduction.Recently, proposed endocrine-related side effects of these agents include alterations in thyroid function, bone metabolism, linear growth, gonadal function, fetal development, glucose metabolism and adrenal function.

Growth impairment is one of the major adverse effect of long-term imatinib treatment in children with CML. Multiple case reports have demonstrated growth retardation in children onimatinib.Imatinibmesylate inhibits the TK activity of BCR-ABL1 and several related TKs, including c-kit and theplatelet-derived growth factor receptor (PDGFR). It isthe inhibition of TK activity at the non-BCR-ABL sites that couldbe the likely cause for the adverse effect on growth. Severalstudies in adults have suggested that inhibition of c-kit,c-fms, and PDGF receptors results in modulation of bone metabolism. Other reports are focusing on disturbance of the growth hormone (GH) axis as a mechanism for growth impairment. Receptor and non receptor TK is expressed at multiple levels in GH-IGF-1 axis including GHRH-R, GH-R and IGF-1R. Inhibition of TKs with TKI, at any one of these level, might result in growth impairment.

Various studies are available to show that Imainib therapy may cause short stature in children on prolonged treatment but exact mechanism by which this occurs is still not clear. Further, no treatment modality has been tried so far, for short stature in these children.

So, the purpose of this study is to study GH-IGF1 axis in these children and to administer GH therapy to GH deficienct children in remission.