Discussion
tumor, breast cancer, cancer, early‐stage breast cancer, tumors
RECURRENCES, TUMOR, BREAST CANCER, CANCER, RECURRENT CANCER, DNA DAMAGE, HEAD AND NECK CANCER, TUMORS
We have shown that protein levels of WRAP53 and To our knowledge, the association between low levels of nuclear WRAP53 and increased risk of locally recurrent cancer has not been shown previously in breast cancer. Thus, the finding of WRAP53 as a prognostic marker for IBTR is new. Previous studies have found that low nuclear levels of WRAP53 correlate with an increased mortality, which is in line with our findings. In head and neck cancer, the association was for overall survival [Expression of SweBCG91RT is a large randomized controlled trial with a very long follow‐up of patients with early‐stage breast cancer, where patients were randomized to postoperative radiotherapy or not. The majority of the tumors were included in both a tissue microarray, allowing for the staining of new markers, and RNA expression analysis. This makes SweBCG91RT an ideal trial for evaluating radiotherapy response in relation to new markers. Potential limitations of this study include that the cohort lacks patients with more advanced stages of breast cancer. However, the patients included represents the majority of women in a modern breast cancer cohort making the results generalizable. Second, few patients were recommended systemic adjuvant treatment at the time, which a majority would have been today. Such treatment would have decreased the risk of recurrences, making our results harder to translate to a modern setting. However, this is also a strength since it gives a unique opportunity to study the effect of radiotherapy without confounding other types of treatment. It is not known how systemic therapy would affect the specific functions of WRAP53. It appears likely that this protein would be activated and participate in the repair of DNA damage caused by various genotoxic agents, as WRAP53 has been shown to be phosphorylated and activated by ATM following various stress conditions [The diverging results between the three WRAP53 expression evaluation methods (C1, C2, and RNA) in regards of prognostic and radiotherapy efficacy predictive abilities indicate that this is a complex subject that calls for further research. The discrepancy is reflected in the weak (or nonexisting) correlation between the results from the different measurements. For the two antibodies, it is likely caused by variation in antibody specificity. C1 and C2 bind to separate sections of the protein and thus potentially different isoforms of the protein. These isoforms could be differently affected by cellular processes, which could contribute to the discrepancy in staining patterns and correlation to outcome. Other contributing factors could be intratumoral heterogeneity and slightly different sections of the tumor being used in the two cores for each antibody and for the two antibodies. Evaluating both cores from each tumor together, rather than separately and choosing the one with the highest fraction of stained tumor cells, would have decreased the effect of a potential intratumoral heterogeneity. However, the correlation of histoscores for the tumor pairs was strong and intratumoral heterogeneity is not considered to have a large impact on the results. As for the discrepancy between protein and RNA levels, the two diagnostics methods differ fundamentally. In gene expression analysis, serial whole sections from formalin‐fixed paraffin‐embedded material are analyzed, incorporating also the In the gene set enrichment analysis, DNA damage response‐related gene pathways, among others, were enriched in tumors with low WRAP53 protein levels. This is in line with the hypothesis that as the tumor progresses, the DNA damage response is activated. Loss of WRAP53 in this situation allows the escape of damaged cancer cells and the formation of even more malignant clones. A tumor cell would likely not be advantaged by complete loss of DNA damage response since that would generate such a large amount of mutations and DNA breaks that the cell was unable to function. However, some reduction in DNA repair function is favorable as this promotes the gain of new oncogenic or loss of tumor suppressor genes. The majority of the differently expressed genes were enriched in tumors with high WRAP53, but this did not correspond to any pathways. This lack of enriched pathways can be due to a large heterogeneity among tumors with high WRAP53 levels.