Cancer Stem Cell Markers in Oral Cancer Tied to Tumor Invasion Depth and Saliva Flow
A pilot study of 12 oral cancer patients links CD133 to deeper tumor invasion and CD166 to lower salivary flow, hinting at new prognostic markers.
Zusammenfassung
Oral squamous cell carcinoma (OSCC) is aggressive, often diagnosed late, and has a five-year survival of about 50%. Researchers in Serbia studied twelve OSCC patients to see whether putative cancer stem cell markers (CD44, CD133, CD166) relate to clinical features. Tumor cells were grown in culture and analyzed by flow cytometry. CD44 was expressed in nearly all cells (median 96.4%), CD166 was moderate to high (85.5%), and CD133 was rare (1.5%). Deeper tumor invasion correlated with more CD133+ cells and CD133 co-expression. Surprisingly, higher CD166 and CD44+/CD166+ levels correlated with lower salivary flow, even though flow was within normal range. With only 12 patients, the findings are preliminary, but they suggest CD133 may be a useful prognostic marker worth testing in larger studies.
Detaillierte Zusammenfassung
Oral squamous cell carcinoma accounts for over 90% of oral cavity cancers. It invades locally and spreads early to cervical lymph nodes. Five-year survival has stayed near 50%, and no validated early screening exists. Conventional clinical and histological factors predict outcomes imperfectly, so researchers are looking at cancer stem cells (CSCs). These are tumor cell subpopulations thought to drive growth, metastasis, therapy resistance, and relapse.
This pilot cross-sectional study enrolled twelve patients (nine men, three women; mean age 65) with histologically confirmed OSCC who underwent primary tumor resection. Most had advanced disease: 58.3% stage III and 33.3% stage IV. TNM stage and tumor dimensions were recorded, and depth of invasion (DOI) was measured histologically. Before treatment, unstimulated salivary flow was measured by sialometry. Tumor tissue was enzymatically dissociated and expanded as primary cultures. Flow cytometry then quantified CD44, CD133, and CD166, including co-expression. Associations were tested with Pearson's correlation.
All samples expressed all three markers, but at very different levels. CD44 was near-universal (range 83.8–99.0%, median 96.4%). CD166 was moderate to high (53.1–99.0%, median 85.5%). CD133 was low (0.3–55.4%, median 1.5%), in line with earlier reports of roughly 1–2% CD133+ cells in OSCC. CD44+/CD166+ co-expression was highest (median 86.6%). CD44+/CD133+ and CD166+/CD133+ were about 1–2%, and triple-positive cells had a median of 2.0%, with a few samples far higher.
Two correlations stood out. Depth of invasion correlated positively with CD133+ cells and with CD133 co-expression (CD44+/CD133+, CD166+/CD133+, and triple-positive; p ≤ 0.05), suggesting CD133 marks a more invasive tumor phenotype. Salivary flow correlated negatively with CD166+ and CD44+/CD166+ cells (p ≤ 0.01). This is a new observation, since saliva is usually studied only after radiotherapy. Flow rates were normal in all patients (mean 0.38 mL/min), so the mechanism is unclear.
The results are hypothesis-generating. They support exploring CD133, and possibly CD166, as prognostic or stratification markers in OSCC. The sample is very small and the design cross-sectional, with no survival or recurrence data. Markers were measured in cultured cells, which may not reflect in-situ tumor biology. Confirming the findings will require larger, longitudinal studies, ideally with tissue-level validation.
Wichtigste Erkenntnisse
- CD44 was expressed in nearly all OSCC tumor cells (median 96.4%), while CD166 was moderate to high (median 85.5%).
- CD133 was rare (median 1.5%) but varied widely, reaching 55.4% in some patients.
- Depth of invasion correlated positively with CD133+ cells and with CD133 co-expression with CD44 and CD166 (p ≤ 0.05).
- Higher CD166+ and CD44+/CD166+ levels correlated with lower salivary flow (p ≤ 0.01), despite normal flow rates in all patients.
- Triple-positive CD44/CD166/CD133 cells were uncommon (median 2.0%) but highly variable across patients.
Methodik
Pilot cross-sectional study of 12 OSCC patients undergoing primary resection. Tumors were dissociated into primary cultures, and CD44, CD133, and CD166 were quantified by flow cytometry. Pearson correlations tested associations with depth of invasion, tumor size, stage, and pre-treatment unstimulated salivary flow.
Studienlimitierungen
Only 12 patients, mostly advanced stage, with no survival or recurrence follow-up and no correction for multiple comparisons, so correlations may be chance findings. Markers were measured in expanded cultured cells rather than intact tissue, which may alter marker expression. Marker specificity for true cancer stem cells was not functionally validated.
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