Evaluation of lymphocyte apoptosis in patients with oral cancer

Abstract

Objectives

To evaluate apoptotic levels of peripheral blood mononuclear cells (PBMCs) and apoptotic regulatory proteins (Bax and Bcl-2) in lymphocyte subsets of oral cancer (OC) patients and healthy controls (HC).

Methodology

The percentage of apoptotic cells and lymphocyte counts were measured in the first cohort using PBMCs obtained from 23 OC patients and 6 HC. In the second cohort, (OC, 33; HC, 13), the mean fluorescence intensity (MFI) of Bax and Bcl-2 in CD19 ⁺ B, CD4 ⁺ T, CD8 ⁺ T, and CD16 ⁺56 ⁺ natural killer (NK) cells was determined via flow cytometry.

Results

The percentage of apoptotic cells was higher in the PBMCs of OC patients than in HC patients, particularly in patients with stage IV cancer ( p<0.05). However, lymphocyte counts were significantly lower in stage IV patients ( p<0.05). NK CD19 ⁺ B and CD16 ⁺56 ⁺ cell counts were significantly lower in OC patients compared with HC patients ( p<0.001 and p<0.01, respectively), but CD4 ⁺ T cells were interestingly significantly higher in OC patients ( p<0.001). While Bax MFI was slightly higher, Bcl-2 MFI was significantly lower for all four lymphocyte subsets in OC samples, particularly in stage IV patients, when compared with HC. Consequently, Bax/Bcl-2 ratios showed an upward trend from HC to OC patients, particularly those in stage IV. We found similar trends in Bax and Bcl-2 MFI for tumor stage, tumor size, and lymph node involvement.

Conclusions

The increased lymphocyte apoptosis in stage IV OC patients may be related to higher Bax levels and lower Bcl-2 levels. The Bax/Bcl-2 ratio in lymphocytes may be useful to determine the prognosis of OC patients, and could be considered a mean for supportive treatment in the future.