Increasing alkaline DNase activity with substrate specificity for denaturated DNA after high dose methotrexate...

Area of Science:

• Biochemistry
• Oncology
• Molecular Biology

Background:

• Osteosarcoma is a primary bone cancer common in children and young adults.
• High-dose methotrexate is a chemotherapy agent used in osteosarcoma treatment.
• Chemotherapy can induce DNA damage and cellular responses, including DNA repair mechanisms.

Purpose of the Study:

• To investigate the effect of high-dose methotrexate therapy on alkaline DNase activity in lymphocytes of children with non-metastatic osteosarcoma.
• To explore the potential role of alkaline DNase in DNA repair following chemotherapy.
• To assess the feasibility of using alkaline DNase activity as a biomarker for monitoring chemotherapy side effects and DNA damage.

Main Methods:

• Measurement of alkaline DNase activity in lymphocytes and PHA-stimulated lymphocytes from children undergoing methotrexate therapy.
• Characterization of the enzyme's properties, including isoelectric point (pI 5.9) and pH optimum (8.5).
• Assessment of magnesium ion (Mg++) requirement for enzyme activation.

Main Results:

• Alkaline DNase activity significantly increased in lymphocytes and PHA-stimulated lymphocytes after high-dose methotrexate therapy.
• The enzyme's activity returned to levels comparable to controls two weeks post-therapy.
• The study identified key enzymatic properties: pI 5.9, pH optimum 8.5, and requirement for Mg++.

Conclusions:

• Alkaline DNase activity in lymphocytes may be involved in DNA repair processes following methotrexate-induced DNA damage.
• Monitoring alkaline DNase activity could serve as a parameter to control chemotherapy side effects.
• This provides an indirect method to demonstrate therapy-induced DNA damage in osteosarcoma patients.