Introduction:
The epithelial mesenchymal transition (EMT) and cancer stem cell (CSC) development
promote therapy resistance in oral squamous cell carcinoma (OSCC), but the mechanisms
behind are not fully understood. Matrix-assisted laser desorption/ionization mass
spectrometry imaging (MALDI-MSI) enables a label-free detection of associated molecules
within cancer tissue with a possible predictive value.
Methods:
UPCI-SCC-026 cells were cultivated under Gefitinib supplementation (5µM) for more
than 12 months (SCC026Gef). To detect differences in phenotype, Gefitinib sensitivity,
and behavior, cell invasion/migration assays, time-dependent cell response profiles
assay (TCRPs), flow cytometry (FCM) and MALDI MSI were performed. Protein-/RNA expression
of EMT/CSC markers were detected by immunofluorescence and RT2 Profiler PCR Arrays.
Results:
SCC026Gef cells show a spindle shaped scattered growth, increased migration/invasion,
and reduced proliferation. The data of FCM and TCRPs indicate a decreased sensitivity
to Gefitinib in SCC026Gef. Protein and mRNA expression analyses show an EGFR upregulation,
a minimal E-cadherin down-regulation, increased expression of collagen 3α1, fibronectin,
and CSC markers (AXL, DLL1, FLOT2, KIT, KIT ligand). A protocol for processing cultured
cells for MALDI-MSI analysis was established. Discriminating imaging patterns of SCC026Gef
can be detected.
Conclusions:
We provide an in vitro model of therapy-induced selection of resistant cell clones
in OSCC with a development of a partial EMT/CSC phenotype by long-term EGFR inhibitor
treatment. Treatment-induced phenotype changes can be revealed by MALDI-MSI. The predictive
value of different imaging patterns of MALDI-MSI has to be validated in further studies.
