Cancer Stem Cells with Overexpression of Neuronal Markers Enhance Chemoresistance and Invasion in Retinoblastoma

Curr Cancer Drug Targets. 2020;20(9):710-719. doi: 10.2174/1568009620666200504112711.

Abstract

Background: Retinoblastoma is a sight and life-threatening embryonal tumor in children. Though chemotherapy is the main mode of therapy, evolving resistance remains a major obstacle in treatment success. The presence of cancer stem cells (CSC) is frequently reported to be responsible for chemoresistance in multiple tumors.

Objective: Our study aims to identify the molecular factors that facilitate the chemoresistance through cancer stem cells in retinoblastoma.

Methods: We developed etoposide and carboplatin resistant retinoblastoma (Y79) cell lines by stepwise drug increment treatment, validated with MTT and TUNEL assays. Colony forming and invasive ability were studied by soft-agar colony forming and transwell assays, respectively. Similar analysis in non-responsive retinoblastoma tumors were carried out by histopathology. Finally, expression of CSC/neuronal markers and ABC transporters were examined by quantitative PCR and protein expression of neuronal stem cell markers was confirmed by Western blot.

Results: Larger colony size of resistant cells in soft-agar assay provided evidence for increased selfrenewability. Histopathology in non-responsive tumors showed poorly differentiated cells predominantly. Besides, both resistant cell lines and non-responsive tumors showed increased invasion with higher expression of neuronal stem cell markers - SOX2, NANOG, OCT4 and ABC transporters - ABCB1 and ABCC3. Increased self-renewal ability and invasion along with overexpression of stemness markers in resistant cells and tumors provide evidence for stemness driving chemoresistance and invasion in retinoblastoma.

Conclusion: We have demonstrated Neuronal stem cell/CSC markers that facilitate the maintenance of cancer stem cells. Developing therapies targeting these factors will help in overcoming resistance and improving retinoblastoma treatment.

Keywords: ABC transporter; Chemoresistance; cancer stem cell; histopathology; neuronal stem cell markers; retinoblastoma.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B / metabolism
  • Antineoplastic Agents, Phytogenic / pharmacology
  • Antineoplastic Agents, Phytogenic / therapeutic use*
  • Apoptosis / drug effects
  • Carboplatin / pharmacology
  • Carboplatin / therapeutic use*
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm* / drug effects
  • Etoposide / pharmacology
  • Etoposide / therapeutic use*
  • Humans
  • Multidrug Resistance-Associated Proteins / metabolism
  • Nanog Homeobox Protein / metabolism
  • Neoplasm Invasiveness
  • Neoplastic Stem Cells / metabolism*
  • Neural Stem Cells / metabolism*
  • Octamer Transcription Factor-3
  • Retinal Neoplasms / drug therapy*
  • Retinal Neoplasms / metabolism*
  • Retinal Neoplasms / pathology
  • Retinoblastoma / drug therapy*
  • Retinoblastoma / metabolism*
  • Retinoblastoma / pathology
  • SOXB1 Transcription Factors / metabolism
  • Signal Transduction

Substances

  • ABCB1 protein, human
  • ATP Binding Cassette Transporter, Subfamily B
  • Antineoplastic Agents, Phytogenic
  • Multidrug Resistance-Associated Proteins
  • NANOG protein, human
  • Nanog Homeobox Protein
  • Octamer Transcription Factor-3
  • POU5F1 protein, human
  • SOX2 protein, human
  • SOXB1 Transcription Factors
  • multidrug resistance-associated protein 3
  • Etoposide
  • Carboplatin