Expression profiles of MGMT, p16, and APC genes in tumor and matching surgical margin from patients with oral squamous cell carcinoma

Comparative Evaluation of Immunohistochemical Expression of p16 with p16 Microsatellite Marker by PCR in Surgical Margins of Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is most common oral cancer with multifactorial etiology. Surgical therapy is treatment of choice but known to have recurrence. The main reason for recurrence is associated with surgical margins which need to be tumor free. Changes at genetic level cannot be ascertained only through routine light microscopy in surgical margins, even though they are tumor free. Detection of early marker like p16 can help in predicting the risk of recurrence. Hence study aimed to detect p16 microsatellite marker (D9s1747) in surgical margins of oral squamous cell carcinoma and compare the same with p16 marker through immunohistochemistry. Total of 40 paraffin embedded tissue samples diagnosed and surgically treated cases of OSCC were included. From each sample one tumor proper and one surgical margin was obtained. From paraffin embedded tissue sample 2 sections of 4 µm thick was obtained from tumor proper and tumor margin. One section was stained with hematoxylin and eosin and other section was stained immunohistochemically using p16 antibody. DNA extraction was done for tumor proper and surgical margin tissue and PCR analysis was carried for p16 microsatellite marker (D91747). Out of 40 cases 37 cases showed positivity in tumor proper for p16 with IHC. Out of 37 cases 23 cases showed positivity for both tumor proper and surgical margin. There were 3 cases negative for tumor proper. Out of these 3 cases, 1 (33.3%) case was positive for surgical margin. Out of 40 cases 27 cases showed positivity for tumor proper with p16 microsatellite marker. Out of 27 cases 16 cases showed positivity for both tumor proper and surgical margin. There were 13 cases negative for tumor proper. However there were 8 (61.5%) cases negative which were in tumor proper but showed positivity for surgical margin. Other 5 cases were negative in both tumor proper and surgical margin. Our study reveals that surgical margins of OSCC exhibit alteration in p16 markers both by IHC and PCR techniques. p16 and p16 microsatellite marker detection in margins indicates field change. Further studies with larger sample size comparing expression with clinical and histological parameter and follow up has to be done to substantiate our findings.

Detection and comparison of microsatellite marker D9S1747 with clinical stages and grades of oral squamous cell carcinoma

Background:

One of the main characteristics of oral squamous cell carcinoma (OSCC) is genetic alteration in specific target regions. Allelic imbalance in tumor suppressor genes is the key event in OSCC which is associated with loss of heterozygosity mostly on chromosome 9p21 locus which includes p16 marker. p16 (D9S1747) is a microsatellite marker which detects early changes in OSCC. To redefine more clearly the role of D9S1747 (p16 microsatellite marker) and its expression in OSCC, the study was designed with the aim to check the detection of D9S1747 in OSCC and to compare the same with histopathological grades and tumor node metastasis staging.

Materials and Methods:

Forty cases of paraffin-embedded tissue section which was histologically confirmed as OSCC and 10 cases of normal tissues were retrieved from the archives. DNA was extracted from the tissue sections and subjected for polymerase chain reaction to detect p16 microsatellite marker D9S1747. Data were analyzed using Chi-square test and Fisher's exact test.

Results:

Twenty-seven cases (67.5%) showed p16 microsatellite marker positivity for OSCC. It was observed that 44.4%, 51.9% and 3.7% p16 microsatellite markers were positive in Stage 1, Stage 2 and Stage 4 OSCC cases, respectively. p16 microsatellite marker positivity was found in 77.8%, 22.2% and 0% for well-differentiated, moderately differentiated and poorly differentiated OSCC cases, respectively.

Conclusion:

The observations of the present study revealed D9S1747 marker as an early event in OSCC, and this can be used as a prognostic marker.

Differential expression of hsa-miR-221, hsa-miR-21, hsa-miR-135b, and hsa-miR-29c suggests a field effect in oral cancer

BACKGROUND

The theory of field effect suggests that the tumor-adjacent area, besides histopathologically normal, undergoes genetic and epigenetic changes that can eventually affect epithelial homeostasis, predisposing the patient to cancer development. One of the many molecular changes described in cancer are microRNAs (miRNAs), which regulates the expression of important genes during carcinogenesis. Thus, the aim of this study was to investigate the field effect in oral cancer.

METHODS

We investigated the differential expression profile of four miRNAs (hsa-miR-221, hsa-miR-21, hsa-miR-135b, and hsa-miR-29c) in cancerous oral tissue, in tumor-adjacent tissue and and in non-cancerous tissue samples from healthy volunteers.

RESULTS

Our results showed significant overexpression profiles of all four studied miRNAs in cancerous oral tissue compared to non-cancerous samples, as well as in tumor-adjacent tissue compared to cancer-free tissue. No significant difference was found when comparing the expression profile of cancerous and tissue-adjacent tissue groups. We found a negative correlation between the expression of hsa-miR-21 expression and STAT3 in oral squamous cell carcinoma.

CONCLUSION

These results suggest that the tissue adjacent to cancer cannot be considered a normal tissue because its molecular aspects are significantly altered. Our data corroborates the hypothesis of field cancerization.