الفهرس 
Oral Squamous Cell Carcinoma
Adult Stem CellsOnly 14 pages are availabe for public view
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Abstract
Oral squamous cell carcinoma remains a major threat to global public health, accounting for more than 90% of all mouth malignancies.In order to develop more effective therapies for this disease, it is essential that we gain a deeper understanding of the biology and the cells that are responsible for recurrent and persistent cancer. Evidence has been accumulating that supports that growth and spread of cancer is driven by a distinct subpopulation of cancer; CSCs which represent the mechanism for cancer tumorigenesis, metastasis, recurrence and treatment failure. Since the study of CSCs in HNSCC has started fairly recently, no single surface marker or method can provide unequivocal identification of CSCs in HNSCCs. Therefore, the identification of more specific CSC markers or a combination of markers and activity assays such as proliferation rate in HNSCC is still needed.
This study was thus conducted to examine the immunohistochemical expression of CSC marker; ALDH1A1, and the proliferation marker; Ki-67 in different grades of OSCC, as well as their correlation with each other in relation to the different OSCC grades through a single-staining protocol. A double IHC staining protocol was also conducted to explore the correlation between both markers on the CSC cellular level for better characterization of CSCs in OSCCs.
Fifty cases of OSCC were selected and classified according to their histopathological features into 20 WD, 16 MD and 14 PD cases of OSCC. Single-staining IHC protocol was carried out using peroxidase-antiperoxidase method where each specimen was stained with either anti-ALDH1A1 or anti-Ki-67 antibodies. In addition, double-staining IHC protocol was performed using peroxidase-antiperoxidase method as well where each specimen was stained with both anti-ALDH1A1 and anti-Ki-67 antibodies sequentially. For result interpretation, with regards to the single-staining methodology, a quantitative assessment of ALDH1A1 and Ki-67 antibody expression was carried out using the image analysis software (Image J, 1.41a, NIH, USA). However, for double-staining protocol, quantitative assessment of ALDH1A1 and Ki-67 antibody expression was performed manually where ALDH1A1 immunopositive cells were considered the positive cases. They were categorized into 2 groups; those that were Ki-67-ve (group 1) and Ki-67+ve (group 2). Positive cases were included in the statistical analysis. For statistical assessment, analysis of variance and Bonferroni test were performed for single-staining protocol where as for double-staining technique; Chi-square test and independent sample t-test were carried out.
Results of the present study revealed that 43 out of 50 OSCC cases (86%) showed positive IHC expression of ALDH1A1, where as 42 out 50 OSCC cases (84%) expressed Ki-67 immunopositivity. Moreover, ALDH1A1 expression has been found to increase along the different grades of OSCC, which was found to be statistically significant. This implies that IHC determination of ALDH1A1+ve CSCs may be clinically useful for the identification of biologically aggressive OSCCs indicating poorer prognosis.
Likewise, Ki-67 immunopositivity was also found to significantly increase along with the grades of OSCC, which indicates a prognostic role for Ki-67 expression in oral cancer patients.
However, both markers were found to increase along with the different grades of OSCC independently where no correlation was found between their expression, except in the MD cases of OSCC where a strong inverse relation was noted. This implies that MD cases of OSCC are the key; they represent the link between these 2 markers in which a switch from a proliferative (WD cases) to an invasive phenotype (PD cases) is noted. The results of the single-staining technique left us with a question; how can ALDH1A1 and Ki-67 expression be inversely related when both markers increase significantly throughout the different OSCC grades?
Analysis of the results of double-stain protocol came to explain this controversy where most of ALDH1A1+ve CSCs were found to be Ki-67-ve (group 1). Moreover, these relatively quiescent CSCs were found to significantly increase along the different grades of OSCC. On the other hand, proliferating CSCs were found to significantly decrease along OSCC grades, although proliferation generally is on the rise, as evidenced by increase in Ki-67 immunopositivity.
Many types of CSCs have been demonstrated in this study, which varied in their distribution, morphology, characteristics and proliferative status. These CSC subsets also seemed to be grade-specific as they varied in their number along the different grades of OSCC. The proliferating CSCs; pre-CSCs and basaloid outer pri-CSCs were more predominant in grades I and II cases (WD cases). Migratory CSCs were most evident in grade III cases of OSCC (MD cases). However, in grade IV cases (PD cases), the quiescent invasive CSCs were more pronounced.