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Pharmacologic modulation of serine/threonine phosphorylation highly sensitizes PHEO in a MPC cell and mouse model to

Lucia Martiniova1, Jie Lu, Jeffrey Chiang

  • 1Reproductive and Adult Endocrinology Program, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America.

Plos One
|February 23, 2011
PubMed
Abstract

Insights

Combining LB1, a PP2A inhibitor, with temozolomide (TMZ) eliminated metastatic pheochromocytoma in mice. This novel approach offers a potential cure for drug-resistant neuroendocrine tumors, achieving long-term survival in 40% of subjects.

Area of Science:

  • Oncology
  • Molecular Biology
  • Pharmacology

Background:

  • Drug-resistant solid tumors, like metastatic pheochromocytoma (PHEO), pose a significant challenge due to cellular heterogeneity.
  • Current cytotoxic chemotherapy often fails to cure these resistant tumors, necessitating novel therapeutic strategies.

Purpose of the Study:

  • To investigate the efficacy of LB1, a serine/threonine protein phosphatase 2A (PP2A) inhibitor, against drug-resistant metastatic PHEO.
  • To evaluate the combined therapeutic effect of LB1 and temozolomide (TMZ) in treating metastatic PHEO.

Main Methods:

  • In vitro studies using a PHEO cell line and in vivo studies using a mouse model of metastatic PHEO.
  • Evaluation of LB1's effect on PP2A inhibition and its impact on cell cycle arrest pathways (p53 and Plk-1).

Main Results:

  • Combination therapy of LB1 and TMZ eradicated metastatic PHEO in a mouse model, leading to long-term, disease-free survival in up to 40% of animals.
  • PP2A inhibition by LB1 prevented p53-mediated G1/S phase arrest and Plk-1-mediated mitotic arrest, crucial defense mechanisms in cancer cells.

Conclusions:

  • Transient inhibition of PP2A can overcome DNA damage-induced defense mechanisms in cancer cells.
  • This strategy enhances the efficacy of non-specific chemotherapy against low-growth fraction, drug-resistant tumors, offering a new therapeutic avenue.

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