Tumor response to neoadjuvant chemoradiation therapy for rectal adenocarcinoma is mediated by p53-dependent and caspase 8-dependent apoptotic pathways

Ki67 expression and localization of T cells after neoadjuvant therapies as reliable predictive markers in rectal cancer

Chemoradiotherapy (CRT) is the standard neoadjuvant therapy for locally advanced rectal cancer (RC). However, neoadjuvant chemotherapy (NAC) also shows favorable outcomes. Although the immunological environment of RC has been thoroughly discussed, the effect of NAC on it is less clear. Here, we investigated the immunological microenvironment, including T cell infiltration, activation, and topological distribution, of resected RC tissue after neoadjuvant therapies and evaluated the correlation between T cell subsets and patient prognosis. Rectal cancer patients (n = 188) were enrolled and categorized into 3 groups, namely CRT (n = 41), NAC (n = 46), and control (surgery alone; n = 101) groups. Characterization of residual carcinoma cells and T cell subsets in resected tissues was performed using multiplex fluorescence immunohistochemistry. The densities of total and activated (Ki67^high) T cells in tissues after NAC, but not CRT, were higher than in control. In both CRT and NAC groups, patients presenting with higher treatment effects showed aggressive infiltration of T cell subsets into carcinomas. Multivariate analyses of pathological and immunological features and prognosis revealed that carcinoma Ki67^highCD4⁺ T cells after CRT and stromal Ki67^highCD8⁺ T cells after NAC are important prognostic factors, respectively. Our results suggest that evaluation of T cell activation with Ki67 expression and its tumor localization can be used to determine the prognosis of advanced RC after neoadjuvant therapies.

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.

Biomarker-Based Scoring System for Prediction of Tumor Response After Preoperative Chemoradiotherapy in Rectal Cancer by Reverse Transcriptase Polymerase Chain Reaction Analysis

BACKGROUND

Numerous molecular markers have been investigated to predict tumor response after preoperative chemoradiotherapy for rectal cancer.

OBJECTIVE

This study aimed to evaluate the predictive value of biomarkers for the prediction of tumor response after preoperative chemoradiotherapy.

DESIGN & SETTING

Tumor specimens have been collected prospectively from 80 patients with rectal cancer who underwent curative resection at 8 weeks after completing preoperative chemoradiotherapy.

MAIN OUTCOME MEASURES

With the use of reverse transcriptase polymerase chain reaction analysis, mRNA expression levels of 7 candidate biomarkers (p53, p21, Ki-67, VEGF, CD133, CD24, and CD44) were evaluated from fresh tumor samples collected before preoperative chemoradiotherapy. The correlation between biomarker expression levels and the pathologic response was assessed based on histopathological staging (pTNM) and tumor regression grade.

RESULTS

The mRNA expression levels of 4 biomarkers (p53, p21, Ki67, and CD133) significantly correlated with tumor regression grade response and pathologic complete response. Patients showing low expression of p53 and/or high expression of p21, Ki67, and CD133 exhibited a significantly greater tumor regression grade response and pathologic complete response rate. A scoring system devised so that 1 point was given for each biomarker whose expression level correlated with pathologic complete response (score range: 0-4) showed that 9 of 62 patients with scores of 0 to 2 achieved pathologic complete response, whereas 15 of 18 patients with scores of 3 to 4 achieved pathologic complete response (14.5% vs 83.3%, p < 0.001). For prediction of pathologic complete response, the scoring system showed 62.5% sensitivity, 94.6% specificity, an 83.3% positive predictive value, and an 85.5% negative predictive value.

LIMITATIONS

Small patient numbers have limitations related to the reproducibility and ability to provide quantitative information. In addition, this study lacks test and validation sets.

CONCLUSIONS

The pretreatment mRNA expression levels of 4 biomarkers correlated with pathologic tumor response after intraoperative chemoradiotherapy in rectal cancer. Furthermore, the scoring system combining values of biomarker expression might have predictive power with high positive and negative predictive values.

Predicting pathological complete response to neoadjuvant chemoradiotherapy in locally advanced rectal cancer: a systematic review

AIM

Approximately 20% of patients treated with neoadjuvant chemoradiotherapy (nCRT) for locally advanced rectal cancer achieve a pathological complete response (pCR) while the remainder derive the benefit of improved local control and downstaging and a small proportion show a minimal response. The ability to predict which patients will benefit would allow for improved patient stratification directing therapy to those who are likely to achieve a good response, thereby avoiding ineffective treatment in those unlikely to benefit.

METHOD

A systematic review of the English language literature was conducted to identify pathological factors, imaging modalities and molecular factors that predict pCR following chemoradiotherapy. PubMed, MEDLINE and Cochrane Database searches were conducted with the following keywords and MeSH search terms: 'rectal neoplasm', 'response', 'neoadjuvant', 'preoperative chemoradiation', 'tumor response'. After review of title and abstracts, 85 articles addressing the prediction of pCR were selected.

RESULTS

Clear methods to predict pCR before chemoradiotherapy have not been defined. Clinical and radiological features of the primary cancer have limited ability to predict response. Molecular profiling holds the greatest potential to predict pCR but adoption of this technology will require greater concordance between cohorts for the biomarkers currently under investigation.

CONCLUSION

At present no robust markers of the prediction of pCR have been identified and the topic remains an area for future research. This review critically evaluates existing literature providing an overview of the methods currently available to predict pCR to nCRT for locally advanced rectal cancer. The review also provides a comprehensive comparison of the accuracy of each modality.

Novel Epigenetic CREB-miR-630 Signaling Axis Regulates Radiosensitivity in Colorectal Cancer

Background

miR-630 has been reported to be a modulator of several cancers, but the mechanism by which is it influences radioresistance remains unknown. We aimed to identify the molecular function of miR-630 and its regulatory mechanism in colorectal cancer (CRC) cell lines.

Methodology

Overexpression and loss-of-function analyses of miR-630 were performed in CRC cell lines by measuring their levels of growth and apoptosis after ionic radiation (IR). Target genes were detected via a dual-luciferase assay and Western blot. Chromatin immunoprecipitation assay was carried out to identify the transcription factor regulating miR-630, and a demethylation experiment was also conducted.

Results

miR-630 expression was found to be positively correlated with radiosensitivity in CRC cell lines (p<0.05). After IR treatment, miR-630 induced apoptosis in cells; however, the opposite was observed when miR-630 was downregulated (p<0.05). BCL2L2 and TP53RK were identified as the target genes of miR-630, and the function of miR-630 was found to depend on these two genes (p<0.05). In addition, evidence showed that CREB regulates the level of miR-630, and demethylation can elevate miR-630 levels (p<0.05).

Conclusion

CREB–miR-630–BCL2L2 and TP53RK comprise a novel signaling cascade regulating radiosensitivity in CRC cell lines by inducing cell apoptosis and death.

Future directions in combined modality therapy for rectal cancer: reevaluating the role of total mesorectal excision after chemoradiotherapy

Most patients who develop rectal cancer present with locoregionally advanced (T3 or node-positive) disease. The standard management of locoregionally advanced rectal cancer is neoadjuvant concurrent chemoradiotherapy (nCRT), followed by radical resection (low-anterior resection or abdominoperineal resection with total mesorectal excision). Approximately 15% of patients can have a pathologic complete response (pCR) at the time of surgery, indicating that some patients can have no detectable residual disease after nCRT. The actual benefit of surgery in this group of patients is unclear. It is possible that omission of surgery in these patients, termed selective nonoperative management, can limit the toxicities associated with standard, multimodal combined modality therapy without compromising disease control. In this review, we discuss the clinical experiences to date using selective nonoperative management and various attempts at escalation of nCRT to improve the number of patients who have a pCR. We also explore several clinical, laboratory, imaging, histopathologic, and genetic biomarkers that have been tested as tools to predict which patients are most likely to have a pCR after nCRT.

P53 status as a predictive biomarker for patients receiving neoadjuvant radiation-based treatment: a meta-analysis in rectal cancer

Background

Numerous studies have yielded inconsistent results regarding the relationship between p53 status and the response to neoadjuvant radiation-based therapy in patients with rectal cancer. We conducted a meta-analysis to clarify the relationship between p53 status and response to radiation-based therapy in rectal cancer.

Methods/Findings

A total of 30 previously published eligible studies including 1,830 cases were identified and included in this meta-analysis. Wild-type form of p53 status (low expression of p53 protein and/or wild-type p53 gene) was associated with pathologic response in rectal cancer patients who received neoadjuvant radiation-based therapy (good response: risk ratio [RR] = 1.30; 95% confidence intervals [CI] = 1.14–1.49; p<0.001; complete response RR = 1.65; 95% CI = 1.19–2.30; p = 0.003; poor response RR = 0.85; 95% CI = 0.75–0.96; p = 0.007). In further stratified analyses, this association remained for sub-groups of good and poor response in neoadjuvant radiotherapy (RT) setting, good and complete response in chemoradiotherapy (CRT) setting. And the association between response and the presence of p53 gene mutations was stronger than that between response and protein positivity.

Conclusion

The results of the present meta-analysis indicate that P53 status is a predictive factor for response in rectal cancer patient undergoing neoadjuvant radiation-based therapy.

The labdane diterpene sclareol (labd-14-ene-8, 13-diol) induces apoptosis in human tumor cell lines and suppression of tumor growth in vivo via a p53-independent mechanism of action

The labdane diterpene sclareol has demonstrated significant cytotoxicity against human tumor cell lines and human colon cancer xenografts. Therefore, there is need to elucidate the mode of action of this compound as very little information is known for the anticancer activity of sclareol and other labdane diterpenes, in general. COMPARE analysis of GI(50) values for a number of human cancer cell lines was initially implicated in an effort to assign a putative mechanism of action to the compound. Sclareol-induced cell cycle arrest and apoptosis were assessed by flow cytometry and Western blot analyses. Finally, the anticancer ability of sclareol in vivo was assessed by using human colon cancer xenograft/mouse models. Sclareol arrested in vitro the growth of p53-deficient (HCT116(p53-/-)) human colon cancer cells and subsequently induced apoptosis by activating both caspases-8 and -9. Intraperitoneal administration of liposome-encapsulated sclareol at the maximum tolerated dose induced a marked growth suppression of HCT116(p53-/-) tumors established as xenografts in immunodeficient NOD/SCID mice. In conclusion, we demonstrate herein that sclareol kills human tumor cells by inducing arrest at the G(1)-phase of the cell cycle followed by apoptosis that involves activation of caspases-8, -9 and -3 via a p53-independent mechanism. These findings suggest that liposome-encapsulated sclareol possesses chemotherapeutic potential for the treatment of colorectal and other types of human cancer regardless of the p53-status.

Bax, cytochrome c, and caspase-8 staining in parotid cancer patients: Markers of susceptibility in radiotherapy?

Objective: Negative bcl-2 and HLA-DR protein expression have been associated with responsiveness to adjuvant radiotherapy in surgically treated parotid cancer patients. The aim of this study was to investigate the prognostic significance of bax, cytochrome c, and caspase-8 protein expression in a group of surgically treated patients to determine whether they also suggest markers of responsiveness to adjuvant radiotherapy.

Study Design: Historical cohort study.

Setting: Otolaryngology department in a university hospital.

Subjects and Methods: The immunohistochemical expression of bax, cytochrome c, and caspase-8 were studied in paraffin-embedded tissue specimens originating from 27 surgically treated parotid cancer patients and nine patients with Warthin parotid tumors (control group) and correlated with the patients' clinicopathological characteristics and clinical outcome.

Results: Caspase-8 negative staining was more frequently observed in higher TNM stages and in tumors measuring more than 4 cm ( P = 0.009 and P = 0.018, respectively). Caspase-8 (−)/cytochrome c (−) patients carried low-grade lesions without nodal involvement ( P = 0.01 and P = 0.05, respectively). Caspase-8 (−) patients who received postoperative radiotherapy presented a significantly increased disease-free survival compared to those who did not ( P = 0.04). Patients bearing bax (−) tumors who received postoperative radiotherapy presented an improved four-year disease-free survival compared to bax (−) patients who did not receive any type of adjuvant radiotherapy ( P = 0.017).

Conclusion: Bax, cytochrome c, and caspase-8 protein expression failed to independently predict survival in parotid cancer patients. However, patients with bax (−) or caspase-8 (−) tumors should be considered as candidates for adjuvant radiotherapy in order to achieve better local disease control.

Novel HIV-1 therapeutics through targeting altered host cell pathways

The emergence of drug-resistant HIV-1 strains presents a challenge for the design of new drugs. Anti-HIV compounds currently in use are the subject of advanced clinical trials using either HIV-1 reverse transcriptase, viral protease or integrase inhibitors. Recent studies show an increase in the number of HIV-1 variants resistant to anti-retroviral agents in newly infected individuals. Targeting host cell factors involved in the regulation of HIV-1 replication might be one way to combat HIV-1 resistance to the currently available anti-viral agents. A specific inhibition of HIV-1 gene expression could be expected from the development of compounds targeting host cell factors that participate in the activation of the HIV-1 LTR promoter. Here we discuss how targeting the host can be accomplished either by using small molecules to alter the function of the host's proteins such as p53 or cdk9, or by utilizing new advances in siRNA therapies to knock down essential host factors such as CCR5 and CXCR4. Finally, we will discuss how the viral protein interactomes should be used to better design therapeutics against HIV-1.

9-Aminoacridine inhibition of HIV-1 Tat dependent transcription

As part of a continued search for more efficient anti-HIV-1 drugs, we are focusing on the possibility that small molecules could efficiently inhibit HIV-1 replication through the restoration of p53 and p21WAF1 functions, which are inactivated by HIV-1 infection. Here we describe the molecular mechanism of 9-aminoacridine (9AA) mediated HIV-1 inhibition. 9AA treatment resulted in inhibition of HIV LTR transcription in a specific manner that was highly dependent on the presence and location of the amino moiety. Importantly, virus replication was found to be inhibited in HIV-1 infected cell lines by 9AA in a dose-dependent manner without inhibiting cellular proliferation or inducing cell death. 9AA inhibited viral replication in both p53 wildtype and p53 mutant cells, indicating that there is another p53 independent factor that was critical for HIV inhibition. p21WAF1 is an ideal candidate as p21WAF1 levels were increased in both p53 wildtype and p53 mutant cells, and p21WAF1 was found to be phosphorylated at S146, an event previously shown to increase its stability. Furthermore, we observed p21WAF1 in complex with cyclin T1 and cdk9 in vitro, suggesting a direct role of p21WAF1 in HIV transcription inhibition. Finally, 9AA treatment resulted in loss of cdk9 from the viral promoter, providing one possible mechanism of transcriptional inhibition. Thus, 9AA treatment was highly efficient at reactivating the p53 – p21WAF1 pathway and consequently inhibiting HIV replication and transcription.

Biological predictive factors in rectal cancer treated with preoperative radiotherapy or radiochemotherapy

We analysed the expression of microsatellite instability, p53, p21, vascular endothelial growth factor and thymidylate synthase (TS) in pretreatment biopsy specimens from 57 locally advanced rectal cancers. The aim of the study was to correlate the expression of these markers with pathological response. Nineteen patients were treated with preoperative concomitant radiotherapy (RT) and fluorouracil/oxaliplatin-based chemotherapy (RCT), while 38 had RT alone. Pathological complete remission (pCR) and microfoci residual tumour (micR) occurred more frequently in patients treated with RCT (P=0.002) and in N0 tumours (P=0.004). Among patients treated with RCT, high TS levels were associated with a higher response rate (pCR+micR; P=0.015). No such correlation was found in the RT group. The other molecular factors were of no predictive value. Multivariate analysis confirmed a significant interaction between nodal status and the probability of achieving a pathological response (P=0.023) and between TS expression and treatment, indicating that a high TS level is predictive of a higher pathological response in the RCT subset (P=0.007). This study shows that lymph node status is the most important predictive factor of tumour response to preoperative treatment. Thymidylate synthase expression assessed immunohistochemically from pretreatment tumour biopsies may be a useful predictive marker of rectal tumour response to preoperative RCT.

Interferon-gamma mediated up-regulation of caspase-8 sensitizes medulloblastoma cells to radio- and chemotherapy

Loss of caspase-8 expression - which has been demonstrated in a subset of Medulloblastoma (MB) - might block important apoptotic signalling pathways and therefore contribute to treatment resistance. In this study, IFN-gamma mediated up-regulation of caspase-8 in human MB cells was found to result in chemosensitization to cisplatin, doxorubicin and etoposide, and sensitisation to radiation. These effects were more prominent in D425 and D341 MB cells (low basal caspase-8 expression) when compared to DAOY MB cells (high basal caspase-8 expression). IFN-gamma mediated chemosensitization and radiosensitization effects were reduced by treatment with the caspase-8 specific inhibitor z-IETD-fmk. Treatment of IFN-gamma resulted in activation of STAT1 in DAOY MB cells and to a lesser extent in D425, but not in D341, indicating that IFN-gamma acts in MB cells through STAT1-dependent and -independent signalling pathways. Taken together, our results demonstrate that IFN-gamma mediated restoration of caspase-8 in MB cells might enhance apoptotic pathways relevant to the response to chemo- and radiotherapy.