EP925 - PAX6: An Epigenetically-Mediated Tumor Suppressor in Anogenital Squamous Cell Carcinomas

ePoster Presenter(s)

• 

  Júlia Pedó Freitas, MD (she/her/hers)

  Resident Physician
  Department of Surgery, UTHSC
  University of Tennessee Health Science Center
  Memphis, Tennessee, United States

  Disclosure information not submitted.

  View ePoster

Author(s)

• AE

  Abul Elahi, PhD

  Research Scientist
  Dept. Surgery, University of Tennessee Health Science Center
  Memphis, Tennessee, United States

  Disclosure information not submitted.
• DW

  Denise Wong, MD, MS

  Physician
  University Hospitals Cleveland
  Cleveland, Ohio, United States

  Disclosure information not submitted.
• LH

  Leah Hendrick, MD, MS

  Physician
  Moffitt Cancer Center
  Tampa, Florida, United States

  Disclosure information not submitted.
• JH

  Jeremiah R. Holt, n/a

  Medical student
  University of Tennessee Health Science Center
  Memphis, Tennessee, United States

  Disclosure information not submitted.
• AA

  Abidemi Ajidahun, MS

  Researcher
  University of Tennessee Health Science Center (UTHSC)
  ARLINGTON, Tennessee, United States

  Disclosure information not submitted.
• IG

  Irina Getun, PhD

  Scientist
  University of Tennessee Health Science Center
  Memphis, Tennessee, United States

  Disclosure information not submitted.
• EG

  Evan S. Glazer, MD

  Associate Professor of Surgery
  The University of Tennessee Health Science Center
  Memphis, Tennessee, United States

  Disclosure information not submitted.

Senior Author(s)

• DS

  David Shibata, MD, FACS, FASCRS

  Professor and Chair of the Department of Surgery
  University of Tennessee Health Science Center
  Memphis, Tennessee, United States

  Disclosure information not submitted.

Purpose/Background: By epigenome-wide analyses, we have previously identified differentially methylated genes in the carcinogenic progression of anal and cervical cancers. Paired box gene 6 (PAX6), a lineage-specific tumor suppressor, was identified as a common target. We examined the impact of PAX6 manipulation in HPV-positive(+) and HPV-negative(-) anal and cervical cancer cell lines.

Methods/Interventions: Promoter methylation status was assessed by quantitative methylation-specific PCR. PAX6 expression was assessed by RT-PCR and Western blotting in HPV16+ cervical (SiHa), HPV18+ cervical (HeLa), HPV- cervical (C33), and HPV16+ anal (ACC) cell lines. The effects of PAX6 modulation by siRNA knockdown and full-length overexpression on cell proliferation (MTT), anchorage-independent growth (soft agar assay) and the transcriptome (RNA-Seq) were assessed.

Results/Outcomes: High baseline PAX6 expression and hypomethylation was confirmed in SiHa, HeLa, and C33, with hypermethylation and absence in ACC. In ACC cells, PAX6 overexpression significantly reduced proliferation and colony formation (both p< 0.001). Conversely, siRNA-mediated knockdown (Fig. 1) in SiHa, HeLa, and C33 increased proliferation [SiHa (p < 0.001), HeLa (p=0.007), C33 (p=0.019)] and colony formation [SiHa (p=0.0056), HeLa (p=0.049), C33 (p=0.048)]. Bulk RNA-Seq analyses demonstrated that PAX6 knockdown significantly altered key oncogenic pathways including upregulation of KRAS signaling (q < 0.001), the immune response (q < 0.001), and MYC signaling (q < 0.001).

Conclusion/Discussion: We have demonstrated that PAX6 is an epigenetically-mediated tumor suppressor in both cervical and anal cancer cell lines and its function appears to be mediated by upregulation of KRAS signaling and MYC-driven oncogenic signaling. Further studies are warranted to examine the role of PAX6 as a biologically significant biomarker of progression and a potential target for preventive and therapeutic strategies.

Figure 1. Proliferation (MTT) and Anchorage-Independent Soft Agar Assay Results