P27 does not predict histopathological response to radiochemotherapy in rectal cancer

Network Mapping of Molecular Biomarkers Influencing Radiation Response in Rectal Cancer

Preoperative radiotherapy (RT) plays an important role in the management of locally advanced rectal cancer (RC). Tumor regression after RT shows marked variability, and robust molecular methods are needed to help predict likely response. The aim of this study was to review the current published literature and use Gene Ontology (GO) analysis to define key molecular biomarkers governing radiation response in RC. A systematic review of electronic bibliographic databases (Medline, Embase) was performed for original articles published between 2000 and 2015. Biomarkers were then classified according to biological function and incorporated into a hierarchical GO tree. Both significant and nonsignificant results were included in the analysis. Significance was binarized on the basis of univariate and multivariate statistics. Significance scores were calculated for each biological domain (or node), and a direct acyclic graph was generated for intuitive mapping of biological pathways and markers involved in RC radiation response. Seventy-two individual biomarkers across 74 studies were identified. On highest-order classification, molecular biomarkers falling within the domains of response to stress, cellular metabolism, and pathways inhibiting apoptosis were found to be the most influential in predicting radiosensitivity. Homogenizing biomarker data from original articles using controlled GO terminology demonstrated that cellular mechanisms of response to RT in RC-in particular the metabolic response to RT-may hold promise in developing radiotherapeutic biomarkers to help predict, and in the future modulate, radiation response.

Immunohistochemical Markers as Predictors of Histopathologic Response and Prognosis in Rectal Cancer Treated with Preoperative Adjuvant Therapy: State of the Art

We explain the state of the art of the immunohistochemical markers of response in rectal cancers treated with neoadjuvant medical therapies and its implication with prognosis. Neoadjuvant chemoradiotherapy is widely used to improve the outcome of patients with locally advanced rectal cancer, and the evaluation of the effects of medical therapy is to date based on histomorphological examination by applying four grading systems of response to therapy (tumor regression grade (TRG)). The need to identify immunohistochemical markers that could ensure a better assessment of response and possibly provide additional prognostic information has emerged. We identified p53, p27kip1, Ki67, matrix metalloprotease-9, survivin, Ki67 proliferative index, CD133, COX2, CD44v6, thymidylate synthase, thymidine phosphorylase, and dihydropyrimidine dehydrogenase as the most common markers studied in literature to date, and we explained their prognostic potential and their implications in the evaluation of the response to preoperative therapies in rectal cancers.

p27 expression in post-treatment rectal cancer: a potential novel approach for predicting residual nodal disease

BACKGROUND

Expression profiles of p21, p27, p53, Ki-67, and thymidylate synthase may be associated with response to neoadjuvant chemoradiation. The relationship between post-treatment protein expression and regional lymph node involvement has not been fully explored.

METHODS

Tumor cores from 126 rectal cancer patients underwent immunohistochemical analysis for the aforementioned proteins. Staining indices (SIs) using percentage of stained cells and staining intensity were calculated for 10 tumor cores per patient. SI for each marker was compared between node negative and node positive patients.

RESULTS

Twenty-six (20.6%) cancer patients had a pathologic complete response and 37 had inadequate tissue or cancer cells, leaving 63 for analysis. Thirty-seven (58.7%) cancer patients were node negative and 26 (41.3%) were node positive. There was an association between increased p27 SI and nodal positivity (P = .04).

CONCLUSION

Increased p27 expression in post-treatment rectal cancer is associated with nodal positivity and may determine which patients are suitable for local excision.

The use of molecular markers as a method to predict the response to neoadjuvant therapy for advanced stage rectal adenocarcinoma

AIM

The response to combined neoadjuvant therapy for advanced stage rectal adenocarcinoma is predictive of outcome. In addition to both clinical and pathological features, the expression of a variety of molecules may provide another method of identifying tumour responsiveness to pre-operative therapy. The aim of this study was to evaluate several markers in the apoptotic pathway as well as expression of Cox-2 and vascular endothelial growth factor (VEGF) to determine their ability to predict response to neoadjuvant therapy.

METHOD

In total, 152 patients with advanced rectal adenocarcinoma were treated with neoadjuvant therapy followed by resection. Paraffin-embedded sections obtained before and after therapy were assessed by immunohistochemical staining for Cox-2, VEGF, p53, p21, p27, Bax, BCL-2 and apoptosis protease-activating factor 1 (APAF-1). These stains were correlated with tumour regression grade, complete pathological response and T-downstaging of the surgical specimen. Clinical and pathological data were also collected. Data were analysed using the χ2 and Spearman's correlation tests.

RESULTS

Pathological complete response was seen in 24.5% of patients. Amongst the apoptosis-associated markers, only APAF-1 expression was found to be significantly associated with tumour regression grade (P<0.001), complete pathological response (P<0.031) and T-downstaging (P<0.004). On multivariate analysis, APAF-1 expression was found to be independently associated with good tumour regression grade. In contrast, overexpression of Cox-2 and VEGF in pretreatment biopsies was related to less tumour regression (P<0.003) and less likelihood of T-downstaging (P<0.03).

CONCLUSION

Immunohistochemical evaluation of initial biopsy specimens of rectal cancer with APAF-1, Cox-2 and VEGF may predict tumour response to neoadjuvant therapy in patients with advanced rectal adenocarcinoma. Those with an expected limited response may be considered for other investigational neoadjuvant protocols.

Chromosomal copy number changes of locally advanced rectal cancers treated with preoperative chemoradiotherapy

Standard treatment of rectal cancer patients comprises preoperative chemoradiotherapy followed by radical surgery. However, clinicians are faced with the problem that response rates vary from one individual to another. Predictive biomarkers would therefore be helpful. To identify genomic imbalances that might assist in stratifying tumors into responsive or nonresponsive categories, we used metaphase comparative genomic hybridization to prospectively analyze pretherapeutic biopsies from 42 patients with locally advanced rectal cancers. These patients were subsequently treated with 5-fluorouracil-based preoperative chemoradiotherapy. Based on downsizing of the T-category, 21 rectal cancers were later classified as responsive, while the other 21 were nonresponsive. Comparing these two groups, we could show that gains of chromosomal regions 7q32 approximately q36 and 7q11 approximately q31, as well as amplifications of 20q11 approximately q13, were significantly associated with responsiveness to preoperative chemoradiotherapy (P<0.05). However, the probability of detecting these copy number changes by chance is high (P=0.21). Our primary results suggest that pretherapeutic evaluation of chromosomal copy number changes may be of value for response prediction of rectal cancers to preoperative chemoradiotherapy. This will require validation in a larger cohort of patients.

Effectiveness of gene expression profiling for response prediction of rectal cancer to preoperative radiotherapy

BACKGROUND

Our aim was to determine whether the expression levels of specific genes could predict clinical radiosensitivity in human colorectal cancer.

METHODS

Radioresistant colorectal cancer cell lines were established by repeated X-ray exposure (total, 100 Gy), and the gene expressions of the parent and radioresistant cell lines were compared in a microarray analysis. To verify the microarray data, we carried out a reverse transcriptase-polymerase chain reaction analysis of identified genes in clinical samples from 30 irradiated rectal cancer patients.

RESULTS

A comparison of the intensity data for the parent and three radioresistant cell lines revealed 17 upregulated and 142 downregulated genes in all radioresistant cell lines. Next, we focused on two upregulated genes, PTMA (prothymosin alpha) and EIF5a2 (eukaryotic translation initiation factor 5A), in the radioresistant cell lines. In clinical samples, the expression of PTMA was significantly higher in the minor effect group than in the major effect group (P = 0.004), but there were no significant differences in EIF5a2 expression between the two groups.

CONCLUSIONS

We identified radiation-related genes in colorectal cancer and demonstrated that PTMA may play an important role in radiosensitivity. Our findings suggest that PTMA may be a novel marker for predicting the effectiveness of radiotherapy in clinical cases.

The prognostic impact of the ubiquitin ligase subunits Skp2 and Cks1 in colorectal carcinoma

BACKGROUND

Loss of the cell-cycle inhibitory protein p27Kip1 is associated with poor prognosis in colorectal carcinoma. The decrease in p27Kip1 levels is the result of increased proteasome-dependent degradation, mediated and rate-limited by its specific ubiquitin ligase subunits S-phase kinase protein (Skp) 2 and cyclin-dependent kinase subunit (Cks) 1. Recently, Skp2 and Cks1 expression were found to be increased in some colorectal carcinomas, but their potential role as prognostic markers for survival is unknown. The present study was undertaken to assess the prognostic value of both Skp2 and Cks1 in colorectal carcinoma.

MATERIALS AND METHODS

The expression of Skp2, Cks1, and p27Kip1 was examined by immunohistochemistry using highly specific antibodies on formalin-fixed, paraffin-embedded tissue sections from 80 patients with colorectal carcinoma.

RESULTS

Overexpression of Skp2 and Cks1 strongly correlated with loss of p27Kip1 and loss of tumor differentiation. A significant decrease in overall survival was observed in patients expressing high Skp2 or Cks1 levels, and in particular, patients with Stage II and III disease. Each protein provided significant additional prognostic information to that given by disease stage, tumor grade, or p27Kip1 expression.

CONCLUSIONS

Results suggest that overexpression of Skp2 or Cks1 is strongly associated with poor prognosis and may thus be used as prognostic markers for overall survival in colorectal carcinoma.

Effectiveness of gene expression profiling for response prediction of rectal adenocarcinomas to preoperative chemoradiotherapy

PURPOSE

There is a wide spectrum of tumor responsiveness of rectal adenocarcinomas to preoperative chemoradiotherapy ranging from complete response to complete resistance. This study aimed to investigate whether parallel gene expression profiling of the primary tumor can contribute to stratification of patients into groups of responders or nonresponders.

PATIENTS AND METHODS

Pretherapeutic biopsies from 30 locally advanced rectal carcinomas were analyzed for gene expression signatures using microarrays. All patients were participants of a phase III clinical trial (CAO/ARO/AIO-94, German Rectal Cancer Trial) and were randomized to receive a preoperative combined-modality therapy including fluorouracil and radiation. Class comparison was used to identify a set of genes that were differentially expressed between responders and nonresponders as measured by T level downsizing and histopathologic tumor regression grading.

RESULTS

In an initial set of 23 patients, responders and nonresponders showed significantly different expression levels for 54 genes (P < .001). The ability to predict response to therapy using gene expression profiles was rigorously evaluated using leave-one-out cross-validation. Tumor behavior was correctly predicted in 83% of patients (P = .02). Sensitivity (correct prediction of response) was 78%, and specificity (correct prediction of nonresponse) was 86%, with a positive and negative predictive value of 78% and 86%, respectively.

CONCLUSION

Our results suggest that pretherapeutic gene expression profiling may assist in response prediction of rectal adenocarcinomas to preoperative chemoradiotherapy. The implementation of gene expression profiles for treatment stratification and clinical management of cancer patients requires validation in large, independent studies, which are now warranted.