Oncogenic PITX2 facilitates tumor cell drug resistance by inverse regulation of hOCT3/SLC22A3 and ABC drug transporters in colon and kidney cancers

Cancer Lett. 2019 May 1:449:237-251. doi: 10.1016/j.canlet.2019.01.044. Epub 2019 Feb 10.

Abstract

Oncogenic pituitary homeobox 2 (PITX2), a de facto master regulator of developmental organ asymmetry, previously upregulated multidrug resistance (MDR) P-glycoprotein ABCB1 in A498 renal cell carcinoma (RCC) cells. The role of PITX2 isoforms in MDR cancers was investigated. Data mining correlated elevated PITX2 in >30% of cancers analyzed, maximally in colon (4.4-fold), confirmed in co-immunostaining of colon and renal cancer microarrays wherein ABCB1 concomitantly increased in RCC. Drug-resistant colorectal adenocarcinoma Colo320DM cells exhibited increased nuclear PITX2 (40-fold), PITX2 promoter activity (27-fold) and ABCB1 (8000-fold) compared to drug-sensitive Colo205. ABCB1 inhibitor PSC833/valspodar or PITX2 siRNA reversed doxorubicin resistance. Nuclei from Colo320DM and A498 cells harbored PITX2A/B1 and PITX2A/B1/B2/Cα/Cβ, respectively. ChIP-qPCR evidenced PITX2 promoter binding in drug exporters ABCB1, ABCC1, ABCG2 and importer hOCT3/SLC22A3. In A498, 786-O, Caki-1, Colo320DM, and Caco2 cells, PITX2 siRNA diminished exporters, increased hOCT3/SLC22A3 expression and activity, and reverted vincristine resistance. Heterologous PITX2 expression induced ABCB1, repressed hOCT3/SLC22A3, enhanced vincristine resistance and diminished proliferation inhibition wherein PITX2A and PITX2C were most effective. Furthermore, PITX2 activity and MDR depended on phosphorylation by GSK3 in A498 cells. Conclusively, oncogenic PITX2 limits sensitizing drug uptake and potentiates cytoprotective drug efflux, contributing to MDR phenotype.

Keywords: ATP binding cassette; Chemoresistance; Developmental pathways in cancer; Homeobox; Organic cation transporter; Transcription factor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter 1 / genetics
  • ATP Binding Cassette Transporter 1 / metabolism*
  • ATP Binding Cassette Transporter, Subfamily G, Member 2 / genetics
  • ATP Binding Cassette Transporter, Subfamily G, Member 2 / metabolism*
  • Antineoplastic Agents / pharmacology
  • Caco-2 Cells
  • Cell Proliferation / drug effects
  • Colonic Neoplasms / drug therapy
  • Colonic Neoplasms / genetics
  • Colonic Neoplasms / metabolism*
  • Doxorubicin / pharmacology
  • Drug Resistance, Multiple* / genetics
  • Drug Resistance, Neoplasm* / genetics
  • Gene Expression Regulation, Neoplastic
  • Glycogen Synthase Kinase 3 / metabolism
  • Homeobox Protein PITX2
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism*
  • Humans
  • Kidney Neoplasms / drug therapy
  • Kidney Neoplasms / genetics
  • Kidney Neoplasms / metabolism*
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Organic Cation Transport Proteins / genetics
  • Organic Cation Transport Proteins / metabolism*
  • Phosphorylation
  • Signal Transduction
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Vincristine / pharmacology

Substances

  • ABCA1 protein, human
  • ABCG2 protein, human
  • ATP Binding Cassette Transporter 1
  • ATP Binding Cassette Transporter, Subfamily G, Member 2
  • Antineoplastic Agents
  • Homeodomain Proteins
  • Neoplasm Proteins
  • Organic Cation Transport Proteins
  • Transcription Factors
  • solute carrier family 22 (organic cation transporter), member 3
  • Vincristine
  • Doxorubicin
  • Glycogen Synthase Kinase 3