Oral Presentation New Zealand Association of Plastic Surgeons Annual Scientific Meeting

Cancer stem cells in head and neck metastatic malignant melanoma (823)

Vithushiya Yoganandarajah 1 , Bede VanSchaijik 1 , Nick Bockett 1 , Helen D Brasch 1 , Erin Paterson 1 , Dalice Sim 2 , Paul F Davis 1 , Tinte Itinteang 1 , Swee T Tan 1 3
  1. Gillies McIndoe Research Institute, Wellington, New Zealand
  2. Biostatistical Group/Dean's Department, University of Otago, Wellington, New Zealand
  3. Wellington Regional Plastic, Maxillofacial and Burns Unit, , Hutt Hospital, Wellington, New Zealand

Background: Malignant melanoma (MM) accounts for 60-80% of skin cancers worldwide with New Zealand and Australia having the highest incidence1,2. Head and neck MM commonly metastasises to the regional lymph nodes. Surgical excision with post-operative adjuvant radiotherapy is the mainstay treatment for nodal metastatic MM. Despite this intensive treatment, the 5-year survival rate for metastatic MM is 5-19%3. Cancer stem cells (CSCs) have been identified in many cancer types including metastatic MM to the brain4. This study identified and characterised CSCs in metastatic head and neck MM (HNmMM) using induced-pluripotent stem cell (iPSC) markers.

Methods: 3,3-Diaminobenzidine (DAB) immunohistochemical (IHC) staining was performed on HNmMM tissue samples from 15 patients, for iPSC markers OCT4, NANOG, SOX2, KLF4 and c-MYC to identify CSCs. Immunofluorescence (IF) IHC staining was performed on two of these samples to localise these markers. Expression of the iPSC markers was investigated by colourimetric in-situ hybridisation (CISH) and reverse-transcription quantitative polymerase chain reaction (RT-qPCR) in 6 HNmMM samples. Two HNmMM-derived primary cell lines underwent tumoursphere formation assays and Western blotting (WB) to investigate cellular functionality and protein expression of the iPSC markers, respectively.

Results:  DAB IHC staining demonstrated expression of OCT4, SOX2, KLF4 and c-MYC in all 15 HNmMM tissue samples while NANOG was present in two of the 15 samples. CISH and RT-qPCR mRNA analyses confirmed transcript expression of all five iPSC markers. IF IHC staining demonstrated an OCT4+/NANOG+/SOX2+/KLF4+/c-MYC+ CSC subpopulation within the tumour nests and the peritumoural stroma; and a further SOX2+/c-MYC+ subpopulation within the tumour nests. HNmMM-derived primary cell lines demonstrated in-vitro tumorsphere formation, and WB confirmed protein expression of SOX2, KLF4 and c-MYC but not OCT4 and NANOG. 

Discussion: This study demonstrated the presence of 3 putative CSC subpopulations within HNmMM.

Conclusions: CSC subpopulations identified maybe a novel therapeutic target for this aggressive cancer.