Prognostic value of Smac expression in rectal cancer patients treated with neoadjuvant therapy

Integrated multiplex analysis of cell death regulators in stage II colorectal cancer suggests patients with 'persister' cell profiles fail to benefit from adjuvant chemotherapy

Objective

Inducing tumour cell apoptosis is a primary objective of chemotherapy but, to date, there are no validated biomarkers of apoptosis sensitivity or resistance. Our objective was to image multiple apoptosis pathway proteins at single cell level and determine multi-protein associations with recurrence risk and chemotherapy response in patients with stage II colorectal cancer (CRC).

Methods and analysis

Multiplexed imaging of 16 proteins in the intrinsic and extrinsic apoptosis pathways at single cell resolution on resected tissue from 194 patients with stage II CRC who either received adjuvant chemotherapy (n=108) or were treated with surgery only (n=86). K-means clustering of >600 000 cancer cells and cell level intensities of APAF1, procaspase-9, procaspase-3, XIAP, SMAC, BAX, BAK, BCL2, BCL-XL, MCL-1, procaspase-8, BID, FADD, FLIP, RIP3 and CIAP1 identified distinct cell cluster profiles.

Results

Chemotherapy-treated patients with a higher percentage of cell clusters with low procaspase-3 and high XIAP had a higher risk of recurrence. This was validated in an independent cohort of adjuvant chemotherapy-treated high-risk patients with stage II CRC. We also applied two established system models of apoptosis initiation and execution to estimate cellular apoptosis sensitivity and show that these cell clusters do not appear to have impaired mitochondrial outer membrane permeabilisation sensitivity, but downstream procaspase-3 cleavage is compromised. This represents a key characteristic of drug-tolerant 'persister' cells.

Conclusion

This study represents the most comprehensive analysis to date of apoptosis protein distribution at single cell level in CRC tumours. Our study identifies a subgroup of patients with stage II CRC with an apoptosis-resistant 'persister' cell profile who do not benefit from adjuvant chemotherapy.

Role of Smac, survivin, XIAP, and Omi/HtrA2 proteins in determining the chemotherapeutic response of patients with cervical cancer treated with neoadjuvant chemotherapy

Neoadjuvant chemotherapy (NACT) followed by radical surgical hysterectomy and pelvic lymph node dissection is considered an effective method to treat patients with bulky stage IB-IIA cervical cancer, but not all patients benefit from NACT. Apoptotic proteins play important roles in the progression of chemotherapy, and second mitochondria-derived activator of caspase (Smac) may have a cooperative relationship with Omi/HtrA2, leading to carcinogenesis and chemotherapy resistance. Chemosensitivity is an important prognostic factor for cervical cancer patients. The aim of this study was to evaluate the significance of Smac, survivin, X-linked inhibitor-of-apoptosis protein (XIAP), and Omi/HtrA2 expression in predicting the response to neoadjuvant chemotherapy and the prognostic significance of te expression of these proteins in cervical cancer patients. Our findings showed that low expression levels of survivin and high expression levels of Omi/HtrA2 in chemotherapy-responsive cervical carcinoma patients significantly increased chemosensitivity.

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.

Can an IL13 -1112 C/T (rs1800925) polymorphism predict responsiveness to neoadjuvant chemoradiotherapy and survival of Chinese Han patients with locally advanced rectal cancer?

We sought to determine whether a polymorphism in the Interleukin 13 gene (IL13), 1112 C/T (rs1800925) predicts responsiveness to neoadjuvant chemoradiotherapy (neoCRT) and prognosis in Chinese Han patients with locally advanced rectal cancer (LARC). Pre-treatment biopsies of primary rectal lesion and surgical specimens were collected from 58 patients with LARC, who were treated with neoCRT and surgery. Tumor DNA was extracted from these biopsies and sequenced to analyze the rs1800925 polymorphism. The tumor response to neoCRT was categorized using a tumor regression grade (TRG, 0-2 were poor responders; 3-4 were good responders). Analyses of progression free survival (PFS) and overall survival (OS) were carried out using the Kaplan-Meier method. Of the forty-six patients for whom tumor DNA was successfully sequenced, 23 were good responders to neoCRT (11 patients with a pathological complete response, i.e. pCR) and the other 23 were poor responders. Good and poor responders were equally likely to have a C/C genotype at rs1800925 (73.9%) as a T/T or C/T genotype (26.1%). There were no differences between the C/C and T/T+C/T genotypes with respect to the ypT0-2 ratio (38.2% vs. 41.7%, P = 1.0), ypN0 nodal status (67.6% vs. 50.0%, P= 0.314), 6-year PFS (67.6% vs. 50%, P=0.274), or 6-year OS (76.5% vs. 66.7%, P=0.441). Thus, the IL13-1112 C/T (rs1800925) polymorphism does not predict responsiveness to neoCRT or prognosis of Chinese Han patients with LARC.

Clinical significance of joint detection of Smac and Caspase9 protein levels in predicting preoperative chemoradiotherapy sensitivity in patients with rectal cancer

AIM: To evaluate the role of second mitochondria-derived activator of Caspase (Smac) and cysteinyl asparate specific proteinase 9 (Caspase9), alone and in combination, in predicting preoperative chemoradiotherapy sensitivity in patients with rectal carcinoma by investigating the relationship between the expression of Smac and Caspase9 and the pathologic response in patients who have received preoperative chemoradiotherapy.

METHODS: The biopsy specimens before chemoradiotherapy and surgical specimens were obtained from 43 cases of rectal adenocarcinoma who received preoperative chemoradiotherapy from July 2008 to June 2013. Immunohistochemical staining was used to test the protein expression levels of Smac and Caspase9, and the relationship between Smac and Caspase9 protein expression levels and postoperative pathological response was analyzed.

RESULTS: The effective rate of preoperative chemoradiotherapy was as high as 72.1%, and the pathological complete response rate was 30.2%. The expression of Smac and Caspase9 was altered after chemoradiotherapy (P < 0.001 for both). Their expression levels were significantly downregulated after chemoradiotherapy. The effective rate of preoperative chemoradiotherapy was significantly increased in patients who were positive for Caspase9 protein expression (staining score range, 1 to 8) before chemoradiotherapy (P < 0.05). And the effective rate was further increased when Smac and Caspase9 proteins were both positive (P = 0.0002). The survival analysis indicated that chemoradiotherapy response was correlated with the overall survival, and the survival was significantly longer in the response arm than in the non-response arm (P = 0.0193).

CONCLUSION: The positive expression of Caspase9 protein in biopsy specimens before chemoradiotherapy can be a marker for sensitivity to radiation and chemotherapy in patients with rectal cancer. Joint detection of Smac and Caspase9 proteins can be more reliable in predicting the sensitivity to preoperative chemoradiotherapy in rectal cancer patients. The response to chemoradiotherapy is a key factor responsible for patients' prognosis. The joint detection of Smac and Caspase9 can be helpful in screening out patients who are sensitive to preoperative chemoradiation.

Smac/DIABLO expression in human gastrointestinal carcinoma: Association with clinicopathological parameters and survivin expression

Lack of apoptosis is a key factor in carcinogenesis and tumor progression. Survivin is a member of the inhibitor of apoptosis protein (IAP) family. Second mitochondria-derived activator of caspases/direct inhibitor of apoptosis-binding protein with low pI (Smac/DIABLO) is an antagonist of IAPs. Recently, Smac/DIABLO was identified as a potent therapeutic target. However, the clinical significance of Smac/DIABLO in gastrointestinal carcinomas remains unclear. In the present study, Smac/DIABLO expression was analyzed by immunohistochemistry in 72 gastric adenocarcinomas and 78 colorectal adenocarcinomas. The expression of Smac/DIABLO was significantly higher in colorectal carcinoma than in gastric carcinoma. Additionally, a correlation was found between the expression of Smac/DIABLO and nuclear survivin in well- to moderately-differentiated colorectal adenocarcinomas (r=0.245; P<0.01). Based on these results, it was hypothesized that gastric and colorectal carcinomas differ in the level of Smac/DIABLO expression. Our previous studies revealed that the expression of cleaved caspase-9 was significantly lower in colorectal carcinoma than in gastric carcinoma (P<0.0001). Conversely, the expression levels of microtubule-associated protein 1 light chain 3 (LC3), an autophagy marker, and survivin were significantly higher in colon cancer than in gastric cancer (P<0.0001 and P<0.01, respectively). Taken together, these results indicate that not only LC3 and survivin expression, but also Smac/DIABLO expression, are significantly higher in colorectal carcinoma than in gastric carcinoma. We hypothesize that the analysis of Smac/DIABLO, survivin and LC3 expression in colorectal carcinoma is likely to aid cancer therapy due to the involvement of these markers in apoptosis and/or autophagy.

Targeting IAP proteins for therapeutic intervention in cancer

Evasion of apoptosis is one of the crucial acquired capabilities used by cancer cells to fend off anticancer therapies. Inhibitor of apoptosis (IAP) proteins exert a range of biological activities that promote cancer cell survival and proliferation. X chromosome-linked IAP is a direct inhibitor of caspases - pro-apoptotic executioner proteases - whereas cellular IAP proteins block the assembly of pro-apoptotic protein signalling complexes and mediate the expression of anti-apoptotic molecules. Furthermore, mutations, amplifications and chromosomal translocations of IAP genes are associated with various malignancies. Among the therapeutic strategies that have been designed to target IAP proteins, the most widely used approach is based on mimicking the IAP-binding motif of second mitochondria-derived activator of caspase (SMAC), which functions as an endogenous IAP antagonist. Alternative strategies include transcriptional repression and the use of antisense oligonucleotides. This Review provides an update on IAP protein biology as well as current and future perspectives on targeting IAP proteins for therapeutic intervention in human malignancies.