There is large evidence implicating COX-2 activity in the development of UBC. Yet, the results obtained in the present study demonstrated that low COX-2 instead of high COX-2 score could predict the recurrence of NMIBC. These results open many questions related to the methodology used in various studies, as well as the complexity in understanding the role of different biological markers in tumorigenesis.
In the present study we used TMA instead of whole tissue section for immunohistochemical analysis. Gudjonsson et al. in their study analyzed COX-2 among different markers on TMA and they found that proteins assessed had no predictive value for recurrences of Ta bladder cancer (BC) . The concerns have been raised by the authors regarding the methodology and generalization of results obtained with TMA in immunohistochemical analysis. Even so we believe that conclusion was made despite the facts that relatively small number of patients (N=52) was analyzed. TMA construction was done with at least three 0.6 mm punch cores and specimens were heterogeneous, including single and multifocal tumors. In order to minimize these problems the present study was conducted on relatively larger number of the patients (N=127), with only single tumor at the time of diagnosis, and with specimens where at least three 1 mm punch could be selected for TMA construction. Nevertheless, the obtained results indicate that different methodology and also diverse scoring system for protein expression could be the reason for different results and conclusion made in different papers.
Previous studies have been conducted mostly on heterogeneous groups of patients with superficial and invasive UBC. One of the first papers in which the expression of COX-1 and COX-2 were analyzed in human invasive TCC of the urinary bladder samples was by Mohammed and coworkers . COX-2 was not expressed in normal urinary bladder samples but was detected in invasive TCC, noninvasive TCC samples, and in cases of carcinoma in situ. Authors concluded that COX-2 may play a role in BC and support further study of COX-2 inhibitors as potential antitumor agents in human BC. After this study several other ones showed significant increase of COX-2 expression with advancing tumor grade and T stages of the disease [22, 23], and not only with disease progression but also with BC specific survival .
Opposite to the role of COX-2 in tumor progression there are also studies where COX-2 expression was not associated with primary tumor stage, lymph node status, histological grading, overall and disease-free survival . Wulfing et al. also did not find COX-2 expression associated with TNM staging, histological grading, overall or disease free survival, but a significant relation to the histological subtype (transitional vs. squamous cell carcinoma) was present . Subgroup of chemotherapy patients demonstrated a significant correlation of strong COX-2 expression with worse overall survival time. The authors concluded that further experimental and clinical studies were needed to elucidate if COX-2 inhibition can serve as an additive therapy to chemotherapy of BC.
There are also several studies analyzing COX-2 expression only in NMIBC. In the CIS group, COX-2 expression was significantly associated with disease recurrence and progression, but not with BC related survival (as in our analysis, data not shown), while in the stage T1 the TCC COX-2 expression was not associated with clinical or pathological parameters or clinical outcome . Kim and coworkers in their study selected only T1G3 TCC who had undergone complete TUR . In that case COX-2 expression was statistically significant in predicting both recurrence and disease progression, while patients’ age, shape and multiplicity of tumors were not significantly predictive. Thus patients, according to authors’ conclusion, with COX-2 positive superficial BC may need to be followed up more vigorously. In the paper of Okajima et al. with only 5 and 6 samples of superficial BC cases with and without recurrence, respectively, after TUR, more COX-2 protein samples in the cases with recurrence than in cases without recurrence were found . Even though the number of cases examined is small, as the authors stated, this result supports their hypothesis that COX-2 contributes to superficial BC recurrence, thus selective COX-2 inhibitors can be a candidate chemo preventive agents for reoccurrence.
Our results differ from the above mentioned because loss of COX-2 was a predictive marker of tumor recurrence. We believe this can be explained by very complex, even different role of this enzyme during tumorigenesis. There is no doubt that COX-2 expression is sequentially up-regulated from normal to chronic cystitis and to malignant changes . Also there are evidence that COX-2 is involved in angiogenesis in BC, as described in the paper where COX-2 promoted vessel proliferation in the tumor zone of pTa/pT1 NMIBC . Moreover, COX-2 is probably up-regulated during tumor progression, as mentioned above, but we believe its role in initial stage is very complex. We hypothesize that, in the initial tumor stage, COX-2 is probably associated with host immunological/inflammatory response and, as such, it could be a marker of sufficient anti-tumor response while loss of COX-2 expression may be indication for the selection of patients for additional immunotherapy. This supposition is also supported by our finding that absence of TILs became the predictor of recurrence. In our study we could not find the association between COX-2 and TILs although there is study by Himly and coworkers in which the association between COX-2 expression and T lymphocyte subsets, CD4+ and CD8+, was confirmed . However, our previous work confirmed the proportion of CD4+ cells and Granzyme B+ TILs being significantly higher in non-recurrent group of patients .