Anti-apoptotic proteins, apoptotic and proliferative parameters and their prognostic significance in cervical carcinoma

Subcellular localization of X-linked inhibitor of apoptosis protein (XIAP) in cancer: does that matter?

X-linked inhibitor of apoptosis protein (XIAP) finely tunes the balance between survival and death to control homeostasis. XIAP is found aberrantly expressed in cancer, which has been shown to promote resistance to therapy-induced apoptosis and confer poor outcome. Despite its predominant cytoplasmic localization in human tissues, growing evidence implicates the expression of XIAP in other subcellular compartments in sustaining cancer hallmarks. Herein, we review our current knowledge on the prognostic role of XIAP localization and discuss molecular mechanisms underlying differential biological functions played in each compartment. The comprehension of XIAP subcellular shuttling and functional dynamics might provide the rationale for future anticancer therapeutics.

Hierarchically targetable fiber rods decorated with dual targeting ligands and detachable zwitterionic coronas

The shapes of drug carriers have significant effects on the drug's blood circulation lifetime and tumor accumulation levels. In this study, nonspherical drug carriers of fiber rods are enhanced with hierarchically targeting capabilities to achieve long circulation in blood, on-demand recovery of cell targeting ligands in tumor tissues and dual ligands-mediated cellular uptake. Zwitterionic polymers are conjugated on fiber rods via acid-labile linkers as stealth coronas to reduce the capture by macrophages and shield the targeting ligands. Compared with commonly used poly(ethylene glycol), the zwitterionic grafts show significantly higher inhibition of protein adsorption and lower internalization by macrophages, leading to around 2 folds longer blood circulation and over 2.5 folds higher drug accumulation in tumors than pristine fiber rods. To address the conflicts between blood circulation and cellular uptake, the zwitterionic coronas are efficiently removed in the slightly acidic tumor microenvironment. The exposure of targeting ligands could activate the internalization by tumor cells, resulting in higher cytotoxicity and tumor accumulation than those with stable linkers. Fiber rods are grafted with dual ligands of folate and biotin, and the optimal ligand densities and ratios are determined to maximize the tumor cell uptake. Compared with other treatment, fiber rods with decorated zwitterionic coronas and acid-liable exposure of dual targeting ligands enhance the suppression of tumor growth, prolong animal survival, and cause less lung metastasis. The development of fiber rods with hierarchically targeting capabilities shows great potential in improving the blood circulation, tumor accumulation and cellular uptake, and eventually promoting therapeutic efficacy. STATEMENT OF SIGNIFICANCE: The targeted delivery of chemotherapeutic agents will encounter a series of biological and pathological barriers. In this study, fiber rods were empowered with hierarchically targeting capabilities to resolve the conflict between blood circulation and cellular uptake. This strategy has shown several advantages over the existing methods. Firstly, zwitterionic polymers were used as blood circulation ligands, and concrete evidence was provided via head-to-head comparison with commonly used poly(ethylene glycol) ligands in the macrophage uptake and in vivo tissue distribution. Secondly, the depletion of circulation ligands and on-demand exposure of targeting ligands in tumor tissues showed crucial effects on the uptake by tumor cells. Thirdly, the densities and ratios of the dual targeting ligands were initially determined for a maximal cellular internalization.

Comprehensive molecular characterization of inhibitors of apoptosis proteins (IAPs) for therapeutic targeting in cancer

Background

Inhibitors of apoptosis proteins (IAPs) are a family of antiapoptotic proteins modulating cell cycle, signal transduction and apoptosis. Dysregulated IAPs have been reported to contribute to tumor progression and chemoresistance in various cancers. However, existing studies were sporadic and only focus on one specific cancer with one particular gene in the IAPs family. A systematic investigation on the co-expression pattern, regulation frameworks on various pathways, prognostic utility on patient outcomes, and predictive value on drug sensitivity among all the IAPs across multiple tumor types was lacking.

Methods

Leveraging The Cancer Genome Atlas data with comprehensive genomic characterizations on 9714 patients across 32 tumor types and the Genomics of Drug Sensitivity in Cancer data with both genomic characterizations and drug sensitivity data on > 1000 cell lines, we investigated the co-expression pattern of IAPs, their regulations of apoptosis as well as other pathways and clinical relevance of IAPs for therapeutics development.

Results

We discovered diverse expression pattern among IAPs, varied spectrum of apoptosis regulations through IAPs and extensive regulations beyond apoptosis involving immune response, cell cycle, gene expression and DNA damage repair. Importantly, IAPs were strong prognostic factors for patient survival and tumor stage in several tumor types including brain, liver, kidney, breast and lung cancer. Further, several IAPs were found to be predictive of sensitivity to BCL-2 inhibitors (BIRC3, BIRC5, BIRC6, and BIRC7) as well as RIPK1 inhibitors (BIRC3 and BIRC6).

Conclusion

Together, our work revealed the landscape of regulations, prognostic utilities and therapeutic relevance of IAPs across multiple tumor types.

WX20120108, a novel IAP antagonist, induces tumor cell autophagy via activating ROS-FOXO pathway

Recently, inhibitor of apoptosis proteins (IAPs) and some IAP antagonists were found to regulate autophagy, but the underlying mechanisms remain unclear. WX20120108 is an analogue of GDC-0152 (a known IAP antagonist) and displays more potent anti-tumor and autophagy-regulating activity in tumor cells, we investigated the regulatory mechanisms underlying WX20120108-induced autophagy. Using molecular docking and fluorescence polarization anisotropy (FPA) competitive assay, we first demonstrated that WX20120108, acting as an IAP antagonist, bound to the XIAP-BIR3, XIAP BIR2-BIR3, cIAP1 BIR3, and cIAP2 BIR3 domains with high affinities. In six cancer cell lines, WX20120108 inhibited the cell proliferation with potencies two to ten-fold higher than that of GDC-0152. In HeLa and MDA-MB-231 cells, WX20120108 induced caspase-dependent apoptosis and activated TNFα-dependent extrinsic apoptosis. On the other hand, WX20120108 induced autophagy in HeLa and MDA-MB-231 cells in dose- and time-dependent manners. We revealed that WX20120108 selectively activated Foxo3, evidenced by Foxo3 nuclear translocation in both gene modified cell line and HeLa cells, as well as the upregulated expression of Foxo3-targeted genes (Bnip3, Pik3c3, Atg5, and Atg4b), which played a key role in autophagy initiation. WX20120108-induced autophagy was significantly suppressed when Foxo3 gene was silenced. WX20120108 dose-dependently increased the generation of reactive oxygen species (ROS) in HeLa cells, and WX20120108-induced Foxo3 activation was completely blocked in the presence of catalase, a known ROS scavenger. However, WX20120108-induced ROS generation was not affected by cIAP1/2 or XIAP gene silencing. In conclusion, WX20120108-induced autophagy relies on activating ROS-Foxo3 pathway, which is independent of IAPs. This finding provides a new insight into the mechanism of IAP antagonist-mediated regulation of autophagy.

Negative correlation between X-linked inhibitors of apoptosis and second mitochondria-derived activator of caspase expression levels in cervical carcinoma and cervical intraepithelial neoplasia

X-linked inhibitors of apoptosis (XIAP) and second mitochondria-derived activator of caspase (Smac) have been widely reported to serve roles in the development of cervical carcinoma. The present study analyzed the associations between the expression levels of XIAP and Smac in normal cervical epithelium, cervical intraepithelial neoplasia (CIN) and cervical carcinoma. Immunohistochemistry staining of formalin-fixed, paraffin-embedded tissue sections was performed in order to analyze the expression levels of XIAP and Smac in 15 cases of normal cervical tissues, 69 cases of CIN and 76 cases of cervical carcinoma. All the tissue samples were confirmed by pathological diagnosis. The association of XIAP and Smac expression levels was analyzed using one-way analysis of variance, χ² tests and Spearman's ρ for the nonparametric bi-variant correlation analysis. Overall survival was determined using the log-rank test and Kaplan-Meier survival curves. The expression level of XIAP was increased in CIN and cervical carcinoma tissues compared with normal cervical tissues, whereas Smac demonstrated a converse expression pattern to XIAP in these tissues. The positive staining level of XIAP protein was increased in grade 3 CIN compared with that in grade 1–2 CIN, and was significantly higher in the less-differentiated tissue of cervical carcinoma compared with the well- or medium-differentiated tissues (P<0.05). The staining level was also significantly increased in cervical carcinoma with stage 2b-3 compared with tissues from stage 1–2a carcinoma (P<0.05). The expression levels of Smac were in opposition to these results. XIAP was associated with pelvic lymph node metastasis, whereas no association was identified with Smac expression. The expression level of XIAP was significantly and negatively associated with cell survival time in cervical carcinoma, whereas the expression level of Smac was significantly and positively associated with cell survival time in cervical carcinoma. Therefore, XIAP and Smac may participate in the development of cervical cancer. The expression levels of XIAP and Smac were significantly and inversely associated. This may be useful in early diagnosis, evaluation of surgery and chemotherapy and the prognosis of cervical carcinoma.

XIAP Interacts with and Regulates the Activity of FAF1

Cell death depends on the balance between the activities of pro- and anti-apoptotic factors. X-linked inhibitor of apoptosis protein (XIAP) plays an important role in the cytoprotective process by inhibiting the caspase cascade and regulating pro-survival signaling pathways. While searching for novel interacting partners of XIAP, we identified Fas-associated factor 1 (FAF1). Contrary to XIAP, FAF1 is a pro-apoptotic factor that also regulates several signaling pathways in which XIAP is involved. However, the functional relationship between FAF1 and XIAP is unknown. Here, we describe a new interaction between XIAP and FAF1 and describe the functional implications of their opposing roles in cell death and NF-κB signaling. Our results clearly demonstrate the interaction of XIAP with FAF1 and define the specific region of the interaction. We observed that XIAP is able to block FAF1-mediated cell death by interfering with the caspase cascade and directly interferes in NF-κB pathway inhibition by FAF1. Furthermore, we show that XIAP promotes ubiquitination of FAF1. Conversely, FAF1 does not interfere with the anti-apoptotic activity of XIAP, despite binding to the BIR domains of XIAP; however, FAF1 does attenuate XIAP-mediated NF-κB activation. Altered expression of both factors has been implicated in degenerative and cancerous processes; therefore, studying the balance between XIAP and FAF1 in these pathologies will aid in the development of novel therapies.

Potential of apoptotic pathway-targeted cancer therapeutic research: Where do we stand?

Underneath the intricacy of every cancer lies mysterious events that impel the tumour cell and its posterity into abnormal growth and tissue invasion. Oncogenic mutations disturb the regulatory circuits responsible for the governance of versatile cellular functions, permitting tumour cells to endure deregulated proliferation, resist to proapoptotic insults, invade and erode normal tissues and above all escape apoptosis. This disruption of apoptosis has been highly implicated in various malignancies and has been exploited as an anticancer strategy. Owing to the fact that apoptosis causes minimal inflammation and damage to the tissue, apoptotic cell death-based therapy has been the centre of attraction for the development of anticancer drugs. Increased understanding of the molecular pathways underlying apoptosis has enabled scientists to establish unique approaches targeting apoptosis pathways in cancer therapeutics. In this review, we reconnoitre the two major pathways (intrinsic and extrinsic) targeted cancer therapeutics, steering toward chief modulators of these pathways, such as B-cell lymphoma 2 protein family members (pro- and antiapoptotic), inhibitor of apoptosis proteins, and the foremost thespian of extrinsic pathway regulator, tumour necrosis factor-related apoptosis-inducing agent. Together, we also will have a look from clinical perspective to address the agents (drugs) and therapeutic strategies adopted to target these specific proteins/pathways that have entered clinical trials.

Association between expression of X-linked inhibitor of apoptosis protein and the clinical outcome in a BRAF V600E-prevalent papillary thyroid cancer population

BACKGROUND

The X-linked inhibitor of apoptosis protein (XIAP) is associated with carcinogenesis, cancer progression, and metastasis through inhibition of the caspase-mediated apoptotic pathway. The BRAF(V600E) mutation is the most common genetic alteration and an established prognostic marker in papillary thyroid cancer (PTC). The prevalence of the BRAF mutation is very high and is up to 80% in Korean PTC patients. In the present study, we evaluated the potential role of XIAP expression as a novel prognostic marker to predict recurrence, in combination with the BRAF(V600E) mutational status.

METHODS

The study enrolled 164 patients with conventional PTC who underwent bilateral thyroidectomy followed by immediate (131)I ablation. The presence of the BRAF(V600E) mutation was evaluated by direct sequencing. The degree of XIAP expression was evaluated by immunohistochemical (IHC) staining using a monoclonal antibody.

RESULTS

The BRAF(V600E) mutation was found in 123 of 164 patients (75%) with classical PTC. XIAP expression was positive in 128 of 164 patients (75%), and positive XIAP expression was significantly associated with the presence of lateral cervical lymph node metastases (p=0.01). XIAP expression was more frequent in BRAF(V600E) mutated PTCs than in BRAF wild type PTCs (p=0.048). The BRAF(V600E) mutation was significantly associated with cancer recurrence in study subjects (hazard ratio=2.98, p=0.039). PTCs positive for the BRAF(V600E) mutation but negative for XIAP expression had a significantly higher rate of recurrent PTC (hazard ratio=4.53, p=0.012).

CONCLUSION

The evaluation of XIAP expression and BRAF mutational analysis was more useful for the prediction of cancer recurrence in patients with PTC than BRAF genotype alone.

Survivin expression correlates with nodal metastasis in T1-T2 squamous cell carcinoma of the tongue

In this study, the correlation between neck metastasis and recurrence was investigated by studying specimens of tongue squamous cell carcinoma patients immunohistochemical with survivin antibodies in the primary biopsy. A retrospective review was conducted at the Academic University Hospital. 46 patients who had squamous cell carcinoma of the tongue, who underwent various types of glossectomy and neck dissections between 1991 and 2008, were evaluated. The patient's sex, TNM staging, differentiation and recurrence rates were analyzed. There were 20 T1 patients and 26 T2 patients; 27 of the patients were N0 and 19 had metastatic lymph nodes in the neck. Survivin antibodies were applied with streptavidin-biotin method to the sections that were prepared from the primary tumor biopsy specimens of the patients. The correlation between neck metastasis and recurrence and survivins' immunohistochemical staining was analyzed with statistical methods. There were no significant differences between the patient's age, sex, tumor's T stage, tumor differentiation and survivin staining density. Survivin staining was positive in 15 (79 %) of 19 patients with neck metastasis, while it was positive in 16 (59 %) of 27 patients without neck metastasis. Eleven (79 %) of the 14 patients who had recurrence and all 6 patients who had neck recurrence only were stained by survivin. Expression of nuclear and cytoplasmic survivin can be a useful marker for predicting cervical lymph node metastasis in T1-T2 tumors in tongue SCC.

IAP proteins as targets for drug development in oncology

The inhibitors of apoptosis (IAPs) constitute a family of proteins involved in the regulation of various cellular processes, including cell death, immune and inflammatory responses, cell proliferation, cell differentiation, and cell motility. There is accumulating evidence supporting IAP-targeting in tumors: IAPs regulate various cellular processes that contribute to tumor development, such as cell death, cell proliferation, and cell migration; their expression is increased in a number of human tumor samples, and IAP overexpression has been correlated with tumor growth, and poor prognosis or low response to treatment; and IAP expression can be rapidly induced in response to chemotherapy or radiotherapy because of the presence of an internal ribosome entry site (IRES)-dependent mechanism of translation initiation, which could contribute to resistance to antitumor therapy. The development of IAP antagonists is an important challenge and was subject to intense research over the past decade. Six molecules are currently in clinical trials. This review focuses on the role of IAPs in tumors and the development of IAP-targeting molecules for anticancer therapy.

XIAP antisense therapy with AEG 35156 in acute myeloid leukemia

INTRODUCTION

AEG 35156 is an antisense oligonucleotide to X-linked inhibitor of apoptosis protein (XIAP). Overexpression of XIAP is common in acute myeloid leukemia (AML) and other cancers and is thought to cause resistance to cancer therapy. Effective treatment options for patients with relapsed or refractory AML are limited and survival continues to be poor. Targeting resistance mechanisms is expected to improve results in relapsed as well as front-line settings.

AREAS COVERED

Role of XIAP in apoptosis pathways, structure of AEG 35156, mechanism of action, pharmacokinetics and pharmacodynamics, clinical efficacy and review of clinical trials in AML.

EXPERT OPINION

AEG 35156 in combination with standard chemotherapy was generally very well-tolerated and had shown some evidence of anti-leukemic activity in AML. The target knock down was transient and has not always correlated with response. Future studies may be done with variations in dose scheduling and with more emphasis on comprehensive pharmacodynamic studies simultaneously analyzing other inhibitor of apoptosis proteins (IAPs) and various XIAP regulators. Use of small molecule mimetics of second mitochondria derived activator of caspases (Smac) simultaneously targeting other IAPs appears to be an attractive option.

Evaluation of pleural fluid survivin and XIAP for the diagnosis of malignant pleural effusion

Survivin and X-linked inhibitor of apoptosis (XIAP) are two inhibitors of apoptosis that are expressed highly in most malignancies and may be diagnostic markers of cancer. The aim of this study was to assess the diagnostic value of survivin and XIAP as tumor markers in malignant pleural effusion. Ninety-eight consecutive patients (including 56 malignant effusions and 42 benign effusions) with pleural effusion were enrolled in the study. Levels of survivin and XIAP mRNA in pleural fluid were measured by reverse transcription polymerase chain reaction. Carcinoembryonic antigen (CEA) was also detected simultaneously. Results showed that levels of survivin and XIAP mRNA were significantly higher in malignant than in benign effusion (P < 0.001 and P = 0.002, respectively). In the diagnosis of malignant pleural effusion, survivin achieved the highest sensitivity (89.3 %) and specificity (95.2 %), as compared with XIAP (66.1 % sensitivity and 85.7 % specificity), or CEA (71.4 % sensitivity and 80.9 % specificity). The combination of survivin and CEA reached 94.6 % sensitivity, with 90.5 % specificity, whereas the combined analysis of survivin and XIAP yielded the highest specificity (95.2 %) and a very good sensitivity (91.1 %). In conclusion, survivin mRNA assay is a useful tumor marker for discriminating malignant from benign pleural effusion. XIAP may be a good candidate for molecular detection of malignant effusion. The combination of survivin and CEA, or XIAP, can increase diagnostic performance.

The Interface between BCR-ABL-Dependent and -Independent Resistance Signaling Pathways in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a clonal hematopoietic disorder characterized by the presence of the Philadelphia chromosome which resulted from the reciprocal translocation between chromosomes 9 and 22. The pathogenesis of CML involves the constitutive activation of the BCR-ABL tyrosine kinase, which governs malignant disease by activating multiple signal transduction pathways. The BCR-ABL kinase inhibitor, imatinib, is the front-line treatment for CML, but the emergence of imatinib resistance and other tyrosine kinase inhibitors (TKIs) has called attention for additional resistance mechanisms and has led to the search for alternative drug treatments. In this paper, we discuss our current understanding of mechanisms, related or unrelated to BCR-ABL, which have been shown to account for chemoresistance and treatment failure. We focus on the potential role of the influx and efflux transporters, the inhibitor of apoptosis proteins, and transcription factor-mediated signals as feasible molecular targets to overcome the development of TKIs resistance in CML.

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.

Nuclear cIAP1 overexpression is a tumor stage- and grade-independent predictor of poor prognosis in human bladder cancer patients

PURPOSE

To evaluate the tumor-related expression profile of cellular inhibitor of apoptosis protein 1 (cIAP1) and cellular inhibitor of apoptosis protein (cIAP2) in patients with bladder cell carcinoma (BCC) and to investigate its potential prognostic value.

METHODS

The expression of cIAP1 and cIAP2 was examined immunohistochemically in archival bladder specimens from 32 normal controls and 102 consecutive patients who underwent surgical operations at our department from January 2004 through December 2005. Cytoplasm cIAP1 and cIAP2 expression was scored as 0 (negative), +1 (weak), +2 (medium), and +3 (strong). Nuclear cIAP1 expression was scored as 0 (0%), +1 (1%-25%), +2 (26%-50%), and +3 (>50%). Proliferation was determined by Ki67 staining as percentage of positive cells.

RESULTS

cIAP1 and cIAP2 expression were significantly increased in bladder cancer compared with normal bladder urothelium (cIAP1-C: P < 0.01, cIAP2-C: P = 0.017, cIAP1-N: P < 0.01). Nuclear staining of cIAP1 (cIAP1-N) was significantly associated with tumor stage (muscle invasive vs. non-muscle invasive, P = 0.03) and tumor grade (low vs. high, P = 0.01). Both the mean overall survival and mean recurrence-free survival were significantly decreased in the high cIAP1-N group compared to the low cIAP1-N group (low cIAP1-N: mean overall survival 62.7 months, high cIAP1-N: mean overall survival 45.6 months, P < 0.01; low cIAP1-N: mean recurrence-free survival 44.2 months, high cIAP1-N: mean recurrence-free survival 30.1 months, P < 0.01). cIAP1-N expression correlated strongly with KI67 expression (r = 0.744, P < 0.01).

CONCLUSION

Nuclear cIAP-1 expression strongly correlated to bladder cancer stage, tumor grade, tumor recurrence and tumor related death. This marker expression was also appears to be a marker in bladder cancer prognosis.

Association of XIAP and P2X7 receptor expression with lymph node metastasis in papillary thyroid carcinoma

The expression of X-linked inhibitor of apoptosis (XIAP) and the P2X7 receptor were demonstrated in a variety of tumors. The purpose of the present study was to investigate the associations of XIAP and P2X7 receptor expression with the clinicopathological features of patients with papillary thyroid carcinoma (PTC). In this cross-sectional study, a total of 62 cases were examined, including 43 patients with PTCs and 19 with benign nodular goiters. XIAP and P2X7 receptor expression were examined by immunohistochemical methods on formalin-fixed, paraffin-embedded thyroid tissues. The staining intensity and extent were evaluated and scored using a semi-quantitative method. The immunohistochemical staining score integrating the intensity and extent of XIAP and P2X7 receptors in PTCs was higher than in nodular goiters. XIAP (OR: 5.6, 95% CI: 1.5-21.1, P=0.009) and P2X7 receptor (OR: 6.1, 95% CI: 1.5-24.4, P=0.007) expression were associated with lymph node metastasis in PTCs. In logistic regression analysis, P2X7 receptor expression, tumor size, and capsular infiltration were predictors for lymph node metastasis (P=0.001). Our results suggested that XIAP and P2X7 receptor expression may predict the aggressiveness of PTC.

Elevated XIAP expression alone does not confer chemoresistance

Background:

In various tumour types, elevated expression of the X-linked inhibitor of apoptosis protein (XIAP) has been observed and XIAP targeting in diverse tumour entities enhanced the susceptibility to chemotherapeutic agents. Therefore, XIAP has been described and reviewed repeatedly as a chemoresistance factor in different tumour entities. However, rather than being an adverse prognostic marker, recent data suggest that elevated XIAP expression may be associated with a favourable clinical outcome. These somewhat conflicting findings, and the fact that in early studies XIAP suppressed apoptosis only when expressed transiently at levels far in excess of its physiological concentration, argue that the function of XIAP as an anti-apoptotic factor in tumour cells is both more complex and diverse than previously appreciated.

Methods:

To better understand the impact of long-term elevated XIAP expression on resistance to chemotherapy, we generated cell lines stably overexpressing XIAP. The role of mitochondria was examined by stable expression of Bcl2 or stable knockdown of second mitochondria-derived activator of caspase (SMAC) in combination with up- or downregulation of XIAP expression.

Results:

Our data show that long-term expression of XIAP at concentrations comparable to that in tumour cells (two- to five-fold increase) resulted in little or no resistance towards chemotherapeutic drugs. The XIAP overexpression only in conjunction with stable knockdown of a single XIAP-antagonising factor such as SMAC resulted in severe resistance to cytostatic agents demonstrating XIAP as a potent chemoresistance factor only in cells lacking functional XIAP regulatory circuits.

Conclusion:

Our results demonstrated that elevated XIAP expression alone cannot serve as a predictive marker of chemoresistance. Our data suggest that in order to predict the impact of XIAP on chemosusceptibility for a given tumour entity, the expression levels and functional states of all XIAP modulators need to be taken into account.

Combined analysis of cell growth and apoptosis-regulating proteins in HPVs associated anogenital tumors

Background

The clinical course of human papillomavirus (HPV) associated with Bowenoid papulosis and condyloma acuminatum of anogenital tumors are still unknown. Here we evaluated molecules that are relevant to cellular proliferation and regulation of apoptosis in HPV associated anogenital tumors.

Methods

We investigated the levels of telomerase activity, and inhibitor of apoptosis proteins (IAPs) family (c-IAP1, c-IAP2, XIAP) and c-Myc mRNA expression levels in 20 specimens of Bowenoid papulosis and 36 specimens of condyloma acuminatum in anogenital areas. Overall, phosphorylated (p-) AKT, p-ribosomal protein S6 (S6) and p-4E-binding protein 1 (4EBP1) expression levels were examined by immunohistochemistry in anogenital tumors both with and without positive telomerase activity.

Results

Positive telomerase activity was detected in 41.7% of Bowenoid papulosis and 27.3% of condyloma acuminatum compared to normal skin (p < 0.001). In contrast, the expression levels of Bowenoid papulosis indicated that c-IAP1, c-IAP2 and XIAP mRNA were significantly upregulated compared to those in both condyloma acuminatum samples (p < 0.001, p < 0.001, p = 0.022, respectively) and normal skin (p < 0.001, p = 0.002, p = 0.034, respectively). Overall, 30% of Bowenoid papulosis with high risk HPV strongly promoted IAPs family and c-Myc but condyloma acuminatum did not significantly activate those genes. Immunohistochemically, p-Akt and p-S6 expressions were associated with positive telomerase activity but not with p-4EBP1 expression.

Conclusion

Combined analysis of the IAPs family, c-Myc mRNA expression, telomerase activity levels and p-Akt/p-S6 expressions may provide clinically relevant molecular markers in HPV associated anogenital tumors.

BRAFV600E mutation and X-linked inhibitor of apoptosis expression in papillary thyroid carcinoma

BACKGROUND

The BRAF mutation V600E (BRAF(V600E)) is the most common genetic alteration in papillary thyroid carcinoma (PTC), while overexpression of X-linked inhibitor of apoptosis (XIAP) has been found in various tumors. Both of these events are implicated in carcinogenesis, tumor progression, recurrence, etc. There are few reports, however, of the BRAF(V600E) mutation and XIAP overexpression in PTC patients. The aim of this study was to investigate the frequency of the BRAF(V600E) mutation in PTC and its relationship to clinicopathological parameters and the expression of XIAP.

METHODS

Genomic DNA was extracted from 123 paraffin-embedded PTC tumor tissue samples and amplified for analysis of the V600E mutation in exon 15 of the BRAF gene by polymerase chain reaction. XIAP expression was examined by immunohistochemical methods in 46 PTCs, 18 benign nodular goiters, and 10 Hashimoto's thyroiditis samples.

RESULTS

The BRAF(V600E) mutation was found in 34.1% of PTC, and was especially prevalent in the classic type. BRAF(V600E) was significantly correlated with younger age at diagnosis (p = 0.026), tumor size (p = 0.009), and histological variants (p = 0.024). There was a trend towards association with extrathyroidal invasion (p = 0.067). By logistic regression analysis, a significant relationship was found between tumor size and the BRAF(V600E) mutation (p = 0.03). XIAP was expressed in 82.6% of PTCs, which was a higher percentage than observed in the group of benign thyroid disorders (35.7%, p < 0.001). Neither the intensity (p = 0.611) nor the extent (p = 0.723) of XIAP staining was correlated with the presence of BRAF(V600E) in PTC patients.

CONCLUSIONS

These data indicate that BRAF(V600E) is associated some of the aggressive clinicopathological features of PTC including younger age at diagnosis, larger tumor size, and classic histological type, as well as also extrathyroidal invasion. XIAP-positive staining was more prevalent in PTCs than in the benign thyroid disorders. Although BRAF(V600E) and XIAP expression are commonly seen in PTC, their presence together seems unrelated.

Stable XIAP knockdown clones of HCT116 colon cancer cells are more sensitive to TRAIL, taxanes and irradiation in vitro

PURPOSE

To develop a model of X-linked inhibitor of apoptosis (XIAP) down regulation in colorectal cancer cell lines. This may be used to determine whether combination strategies have clinical potential.

METHODS

A series of clones were developed using short hairpin RNA (shRNA) against XIAP stably expressed in HCT116 cells. XIAP mRNA and protein levels were established by RT-PCR and Immunoblot, respectively. GeneChip microarrays confirmed XIAP knockdown and absence of compensation by other IAP members.

RESULTS

Four XIAP knockdown cell lines show 82-93% reduction in XIAP mRNA and 67-89% reduction in protein when compared to four luciferase control cell lines. XIAP knockdown sensitises cells to rhTRAIL by a factor of 3, to paclitaxel and docetaxel by a factor of >2 and, to a lesser extent, radiotherapy (20% enhancement).

CONCLUSIONS

Clinical trials with XIAP antisense continue, and these data suggest combination studies with agents such as rhTRAIL and taxanes should be undertaken.

IAP-targeted therapies for cancer

DNA damage, chromosomal abnormalities, oncogene activation, viral infection, substrate detachment and hypoxia can all trigger apoptosis in normal cells. However, cancer cells acquire mutations that allow them to survive these threats that are part and parcel of the transformation process or that may affect the growth and dissemination of the tumor. Eventually, cancer cells accumulate further mutations that make them resistant to apoptosis mediated by standard cytotoxic chemotherapy or radiotherapy. The inhibitor of apoptosis (IAP) family members, defined by the presence of a baculovirus IAP repeat (BIR) protein domain, are key regulators of cytokinesis, apoptosis and signal transduction. Specific IAPs regulate either cell division, caspase activity or survival pathways mediated through binding to their BIR domains, and/or through their ubiquitin-ligase RING domain activity. These protein-protein interactions and post-translational modifications are the subject of intense investigations that shed light on how these proteins contribute to oncogenesis and resistance to therapy. In the past several years, we have seen multiple approaches of IAP antagonism enter the clinic, and the rewards of such strategies are about to reap benefit. Significantly, small molecule pan-IAP antagonists that mimic an endogenous inhibitor of the IAPs, called Smac, have demonstrated an unexpected ability to sensitize cancer cells to tumor necrosis factor-alpha and to promote autocrine or paracrine production of this cytokine by the tumor cell and possibly, other cells too. This review will focus on these and other developmental therapeutics that target the IAPs in cancer.

hCG beta expression by cervical squamous carcinoma--in vivo histological association with tumour invasion and apoptosis

AIMS

To investigate the correlation of beta-subunit of human chorionic gonadotrophin (hCG beta) expression by cervical carcinomas with measures of tumour apoptosis.

METHODS AND RESULTS

Eighty-nine cervical carcinoma patients' samples were subject to hCG beta immunohistochemistry and scored with respect to intensity of immunopositivity and percentage of positive cells. Apoptosis was evaluated by three independent parameters: morphological characteristics [haematoxylin and eosin (H&E)], terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling (TUNEL) and poly (ADP-ribose) polymerase (PARP) immunopositivity. Of the 12 adenocarcinomas, only one (8%) was hCG beta+. However, 87% (61/70) of the squamous cell and 100% (7/7) of adenosquamous cell carcinomas were hCG beta+. hCG beta reactivity and intensity was predominantly confined to peripheral tumour cells at the stromal-epithelial interface. Correlation analysis showed that H&E and PARP apoptotic immunopositivity negatively correlated with hCG beta expression (P < 0.001 and P = 0.028 respectively), whereas TUNEL did not (P = 0.12). However, immunopositivity for apoptotic cells by TUNEL was significantly less in tumours where hCG beta expression was greater (scoring >or= 6) and vice versa. hCG beta immunopositivity was also observed in newly formed blood vessels, as well as tumour cells within lymphatic vessels. When tumour vascularization was taken into account, samples with noted vascularization positively correlated with hCG beta scoring.

CONCLUSIONS

hCG beta expression correlates with reduced tumour cell apoptosis and may be involved in tumour vascularization and dissemination.

Expression of cIAP-1 correlates with nodal metastasis in squamous cell carcinoma of the tongue

Cellular inhibitor-of-apoptosis protein 1 (cIAP-1) is a member of the inhibitor-of- apoptosis protein family, which predominantly regulates apoptosis. It has been suggested that expression of cIAP-1 correlates with certain clinicopathological features. The possible significance of cIAP-1 expression in cervical lymph node metastasis of tongue squamous cell carcinoma (SCC) is investigated. Seventy-five tongue SCCs were analyzed by immunohistochemistry. cIAP-1 immunoreactivity patterns were nuclear in 38 (51%), cytoplasmic in 47 (63%), and concurrent in 37 (49%) cases. Nuclear, cytoplasmic and concurrent cIAP-1 immunoreactions were significantly correlated with lymph node metastasis in tongue SCCs (P=0.0011, 0.0012, and 0.0006, respectively). The cleaved caspase-3, which is a marker of tumor apoptosis, and Ki-67 index, which is a marker of tumor proliferation, were immunohistochemically examined in 21 tongue SCCs with concurrent nuclear and cytoplasmic cIAP-1 expression and with metastasis, and in 23 tongue SCCs without concurrent nuclear and cytoplasmic cIAP-1 expression and without metastasis. Concurrent cIAP-1 expression was inversely correlated with caspase-3 (P=0.0066), but was positively correlated with Ki-67 expression (P=0.0028). The mode of invasion was associated with lymph node metastasis (P=0.014) and differentiation (P=0.013), but was not correlated with cIAP-1 expression. There was no statistically significant correlation between nuclear or cytoplasmic cIAP-1 expression and the clinicopathological factors of gender, age, clinical stage or differentiation. These results suggest that both patterns of cIAP-1 are useful markers for predicting cervical lymph node metastasis in tongue SCC.

Comparative proteomic analysis of low stage and high stage endometrioid ovarian adenocarcinomas

Ovarian cancer, the second most common gynecological malignancy, accounts for 3% of all cancers among women in the United States, and has a high mortality rate, largely because existing therapies for widespread disease are rarely curative. Ovarian endometrioid adenocarcinoma (OEA) accounts for about 20% of the overall incidence of all ovarian cancer. We have used proteomics profiling to characterize low stage (FIGO stage 1 or 2) versus high stage (FIGO stage 3 or 4) human OEAs. In general, the low stage tumors lacked p53 mutations and had frequent CTNNB1, PTEN, and/or PIK3CA mutations. The high stage tumors had mutant p53, were usually high grade, and lacked mutations predicted to deregulate Wnt/β-catenin and PI3K/Pten/Akt signaling. We utilized 2-D liquid-based separation/mass mapping techniques to elucidate molecular weight and pI measurements of the differentially expressed intact proteins. We generated 2-D protein mass maps to facilitate the analysis of protein expression between both the low stage and high stage tumors. These mass maps (over a pI range of 5.6-4.6) revealed that the low stage OEAs demonstrated protein over-expression at the lower pI ranges (pI 4.8-4.6) in comparison to the high stage tumors, which demonstrated protein over-expression in the higher pI ranges (pI 5.4-5.2). These data suggest that both low and high stage OEAs have characteristic pI signatures of abundant protein expression probably reflecting, at least in part, the different signaling pathway defects that characterize each group. In this study, the low stage OEAs were distinguishable from high stage tumors based upon the proteomic profiles. Interestingly, when only high-grade (grade 2 or 3) OEAs were included in the analysis, the tumors still tended to cluster according to stage, suggesting that the altered protein expression was not solely dependent upon tumor cell differentiation. Further, these protein profiles clearly distinguish OEA from other types of ovarian cancer at the protein level.

Expression of deltaNp73 and TAp73alpha independently associated with radiosensitivities and prognoses in cervical squamous cell carcinoma

PURPOSE

The p73 gene produces different protein isoforms using alternative promoters and splicing, which have different biological characteristics. This study was to investigate the expression patterns of two distinct p73 isoforms (deltaNp73 and TAp73alpha) in cervical squamous cell carcinomas (SCC) and the relationship between their expressions and prognostic significance in cervical SCC patients.

EXPERIMENTAL DESIGN

We investigated the protein expressions of deltaNp73 and TAp73alpha in 117 cervical SCC and 113 normal cervical tissues using immunohistochemistry. The expression levels were analyzed with clinical variables and patients' survival.

RESULTS

DeltaNp73and TAp73alpha were significantly overexpressed in cervical SCC compared with those in normal cervical epithelium (P < 0.001). However, their expressions were inversely correlated (P < 0.001, R = -0.368) and associated with differential tumor radiosensitivity. Overexpression of deltaNp73 was significantly found in SCC resistant to irradiation (P < 0.001), whereas increase of TAp73alpha expression was observed in the majority of SCC sensitive to irradiation (P < 0.001). Multivariate and survival analyses indicated that the expressions of deltaNp73 and TAp73alpha were independently associated with prognosis: deltaNp73 was associated with recurrence of the disease [P = 0.001; odds ratio (OR), 4.857] and an adverse outcome (P = 0.012; OR, 4.676), whereas TAp73alpha predicted a better survival of cervical SCC patients (P = 0.018; OR, 0.065).

CONCLUSIONS

The p73 gene might be an important determinant of cellular response to irradiation. The expressions of the two main isoforms (deltaNp73 and TAp73alpha) might be potential markers for predicting the prognosis and sensitivity to radiotherapy in patients with cervical SCC.

Immunohistochemical detection of the X-linked inhibitor of apoptosis protein (XIAP) in cervical squamous intraepithelial neoplasia and squamous carcinoma

Premalignant and invasive squamous lesions of the uterine cervix were surveyed for the immunohistochemical detectability of the X-linked inhibitor of apoptosis protein (XIAP), believed to be the most potent of a novel group of proteins designated inhibitor of apoptosis proteins (IAPs). IAPs bind and prevent the activation of apoptosis-mediating caspases. Recent cancer biologic studies have implicated IAPs in therapeutic resistance and tumor aggressiveness. XIAP in particular is considered a highly promising target for drug discovery. Forty-four formalin-fixed and paraffin-embedded archival tissue sections were deparaffinized; subjected to citrate-based antigen retrieval; and immunostained with anti-XIAP monoclonal antibody (clone 48, BD Biosciences, San Jose, Calif) diluted 1:250, 4 degrees C x 72 hours; and developed using EnVision-Plus (Dako, Carpinteria, Calif) and diaminobenzidine as chromagen. Particulate or heterogeneous cytoplasmic staining was considered positive. Normal squamous epithelium was XIAP-positive in 7 of 34 cases (20.6%). Preinvasive intraepithelial lesions were positively stained in 54.5% of cases. Nineteen of 22 invasive squamous carcinomas were positive (86.4%). The intensity and extensiveness of XIAP immunostaining varied among individual cases, but trended upward with loss of tumor differentiation: 8 of 9 cases with strong staining were poorly differentiated carcinomas. The present study suggests the characteristic link between poor tumor differentiation and more aggressive clinical behavior could in some malignancies be based upon the concomitant induction of XIAP. Induction of XIAP appears to occur in a subset of intraepithelial lesions; in others, XIAP is detected only upon progression to invasive carcinoma. Detection of enhanced XIAP expression may also pinpoint those lesions that might benefit from pharmacologic disruption of XIAP's actions.

Immunohistochemical detection of X-linked inhibitor of apoptosis (XIAP) in neoplastic and other thyroid disorders

The X-linked inhibitor of apoptosis (XIAP) is the most potent of the inhibitors of apoptosis, a group of related caspase inhibitors. X-linked inhibitor of apoptosis expression correlates with radio- and chemoresistance and clinical aggressiveness in certain tumors. XIAP expression was examined in 106 specimens from neoplastic and other thyroid disorders, which underwent citrate-based antigen retrieval and staining with monoclonal anti-XIAP. Normal thyroid was XIAP-negative. Of 35 papillary thyroid carcinomas (PTCs), 29 (83%) stained variably in intensity and/or extent. An insular carcinoma was strongly positive and 1 of 4 anaplastic carcinomas moderately positive. Follicular, medullary, and 3 of 4 anaplastic carcinomas, oncocytic neoplasms, and a hyalinizing trabecular tumor were nonstaining. Hashimoto's thyroiditis and adenomatous goiters were either nonstaining or occasionally stained in oncocytic foci. Because XIAP was highly specific for PTC among the thyroid neoplasms, it may be a useful marker for differential diagnosis when used alone or in combination with other markers. XIAP may also be useful in differentiating insular carcinoma from follicular neoplasm in certain difficult cases. In addition, the selective expression of XIAP in PTC and some high-grade thyroid malignancies also provides clues to the role of the apoptotic pathway in the tumorigenesis of these neoplasms.

Disturbed expression of the apoptosis regulators XIAP, XAF1, and Smac/DIABLO in gastric adenocarcinomas

Dysregulation of apoptosis plays an important role in carcinogenesis and tumor progression. Whereas x-linked inhibitor of apoptosis (XIAP) is a potent inhibitor of apoptosis, its antagonists second mitochondria-derived activator of caspases/direct IAP binding protein with low PI (Smac/DIABLO), and XIAP-associated factor 1 (XAF1) promote apoptosis. To explore the relevance of XIAP, Smac/DIABLO, and XAF1 for carcinogenesis and tumor progression, we analyzed 46 primary gastric adenocarcinomas and non-neoplastic gastric mucosa samples by quantitative real-time polymerase chain reaction. XIAP, Smac/DIABLO, and XAF1 expression was found in all non-neoplastic gastric mucosa samples and all adenocarcinomas. XIAP expression levels did not change between non-neoplastic gastric mucosa and adenocarcinomas or between carcinomas of early and advanced stages. Although Smac/DIABLO expression was significantly (P=0.01) higher in carcinomas, the ratio of XIAP to Smac/DIABLO expression remained stable between non-neoplastic mucosa and carcinomas. XAF1 expression had the tendency to decrease from non-neoplastic mucosa to advanced adenocarcinomas. Importantly, the ratio of XIAP to XAF1 expression significantly (P=0.03) increased from non-neoplastic mucosa to adenocarcinomas and the increase was even higher in carcinomas of advanced stage (P=0.01). Moreover, expression of the XAF1 splice variants differing in the zinc-finger domain essential for XIAP-binding was analyzed and revealed a significant higher (P=0.03) variant-2/variant-1 ratio in advanced carcinomas. In conclusion, an increased expression ratio of XIAP to XAF1 in combination with a disturbed expression of the XAF1 splice variants could be shown in gastric adenocarcinomas. These marked imbalances probably result in an impaired ability for XAF1 to antagonize the effects of XIAP thereby contributing to apoptosis-resistance and generating an important growth advantage.

Immunohistochemical detection of antiapoptotic protein X-linked inhibitor of apoptosis in mammary carcinoma

An immunohistochemical survey of X-linked inhibitor of apoptosis (XIAP) expression in mammary carcinoma was performed. XIAP, the most potent of the inhibitor of apoptosis family of caspase inhibitors, has been linked to tumor aggressiveness and therapeutic resistance in several malignancies and is considered an attractive target for cancer drug discovery. Routinely processed sections from 94 ductal carcinomas, 9 lobular carcinomas, and 10 ductal carcinomas with lobular components or features were subjected to citrate-based antigen retrieval, immunostained with anti-XIAP (BD Biosciences, Franklin Lakes, NJ), Envision+ reagents (Dako, Carpinteria, CA), and diaminobenzidine. Positive staining was found in 22.7% of grade 1, 44% of grade 2, and 89.5% of grade 3 ductal carcinomas. Strong staining occurred in no cases of grade 1, 13% of grade 2, and 55.2% of grade 3 ductal carcinomas. XIAP staining increased overall with grade of ductal carcinoma in situ as well. The staining intensity of invasive carcinoma correlated with that of the corresponding ductal carcinoma in situ in 70% of cases. Ductal carcinomas overall showed more staining than lobular carcinomas. XIAP is most strongly and commonly detected in grade 3 ductal carcinoma. The degree of XIAP expression appears frequently to be determined in the preinvasive intraductal phase of tumorigenesis. These findings suggest a possible role of XIAP in the more aggressive clinical behavior of grade 3, compared with lower-grade ductal carcinomas.

Targeting the apoptotic machinery in pancreatic cancers using small-molecule antagonists of the X-linked inhibitor of apoptosis protein

Resistance to apoptosis is a hallmark of many solid tumors, including pancreatic cancers, and may be the underlying basis for the suboptimal response to chemoradiation therapies. Overexpression of a family of inhibitor of apoptosis proteins (IAP) is commonly observed in pancreatic malignancies. We determined the therapeutic efficacy of recently described small-molecule antagonists of the X-linked IAP (XIAP) in preclinical models of pancreatic cancer. Primary pancreatic cancers were assessed for XIAP expression by immunohistochemistry, using a pancreatic cancer tissue microarray. XIAP small-molecule antagonists ("XAntag"; compounds 1396-11 and 1396-12) and the related compound 1396-28 were tested in vitro in a panel of human pancreatic cancer cell lines (Panc1, Capan1, and BxPC3) and in vivo in s.c. xenograft models for their ability to induce apoptosis and impede neoplastic growth. In addition, pancreatic cancer cell lines were treated with XAntags in conjunction with either tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or with radiation to determine potential synergy for such dual targeting of the apoptotic machinery. XIAP was overexpressed in 14 of 18 (77%) of primary pancreatic cancers. The XAntags1396-11 and 1396-12, but not the inactive isomer 1396-28, induced profound apoptosis in multiple pancreatic cancer cell lines tested in vitro, with a IC(50) in the range of 2 to 5 mumol/L. Mechanistic specificity of the XAntags for the baculoviral IAP repeat-2 domain of XIAP was shown by preferential activation of downstream "effector" caspases (caspase-3 and caspase-7) versus the upstream "initiator" caspase-9. S.c. BxPC3 xenograft growth in athymic mice was significantly inhibited by monotherapy with XAntags; treated xenografts showed marked apoptosis and increased cleavage of caspase-3. Notably, striking synergy was demonstrable when XAntags were combined with either TRAIL or radiation therapy, as measured by growth inhibition in vitro and reduced colony formation in soft agar of pancreatic cancer cell lines, at dosages where these therapeutic modalities had minimal to modest effects when used alone. Finally, XAntags in combination with the standard-of-care agent for advanced pancreatic cancer, gemcitabine, resulted in significantly greater inhibition of in vitro growth than gemcitabine alone. Our results confirm that pharmacologic inhibition of XIAP is a potent therapeutic modality in pancreatic cancers. These antagonists are independently capable of inducing pancreatic cancer cell death and also show synergy when combined with proapoptotic ligands (TRAIL), with radiation, and with a conventional antimetabolite, gemcitabine. These preclinical results suggest that targeting of the apoptotic machinery in pancreatic cancers with XAntags is a promising therapeutic option that warrants further evaluation.

E3 ubiquitin ligases as cancer targets and biomarkers

E3 ubiquitin ligases are a large family of proteins that are engaged in the regulation of the turnover and activity of many target proteins. Together with ubiquitin-activating enzyme E1 and ubiquitin-conjugating enzyme E2, E3 ubiquitin ligases catalyze the ubiquitination of a variety of biologically significant protein substrates for targeted degradation through the 26S proteasome, as well as for nonproteolytic regulation of their functions or subcellular localizations. E3 ubiquitin ligases, therefore, play an essential role in the regulation of many biologic processes. Increasing amounts of evidence strongly suggest that the abnormal regulation of some E3 ligases is involved in cancer development. Furthermore, some E3 ubiquitin ligases are frequently overexpressed in human cancers, which correlates well with increased chemoresistance and poor clinic prognosis. In this review, E3 ubiquitin ligases (such as murine double minute 2, inhibitor of apoptosis protein, and Skp1-Cullin-F-box protein) will be evaluated as potential cancer drug targets and prognostic biomarkers. Extensive study in this field would lead to a better understanding of the molecular mechanism by which E3 ligases regulate cellular processes and of how their deregulations contribute to carcinogenesis. This would eventually lead to the development of a novel class of anticancer drugs targeting specific E3 ubiquitin ligases, as well as the development of sensitive biomarkers for cancer treatment, diagnosis, and prognosis.

Apoptotic effect of fludarabine is independent of expression of IAPs in B-cell chronic lymphocytic leukemia

Despite the efficiency of fludarabine in the induction of clinical responses in B-cell chronic lymphocytic leukemia (B-CLL) patients, resistance to this drug has been documented. The present study tested whether resistance to fludarabine is related to the expression of inhibitor of apoptosis proteins (IAPs) family members. We analyzed the expression of c-IAP1, c-IAP2 and XIAP, by immunocytochemistry, in 30 blood samples from B-CLL patients and correlated protein expression to fludarabine-induced apoptosis estimated by an annexin-V assay. Expression of c-IAP1, c-IAP2 and XIAP were found predominantly in the cytoplasm, and a wide range of staining intensities was observed among distinct samples. No correlation was found between the levels of IAPs expression and prognostic factors such as age, gender, lymphocyte doubling time, white blood cell count or previous treatment. The expression of IAPs also failed to predict the sensitivity to fludarabine-induced apoptosis. Alternative pathways of cell death may explain the independence of fludarabine-induced apoptosis from the high expression of IAPs.

XIAP is related to the chemoresistance and inhibited its expression by RNA interference sensitize pancreatic carcinoma cells to chemotherapeutics

OBJECTIVES

To explore the exact role does the x-linked inhibitor of apoptosis (XIAP) play in chemoresistance of pancreatic carcinoma cell and the cell sensitivity to chemotherapeutic drugs changed after XIAP is inhibited by RNA interference (RNAi).

METHODS

Pancreatic carcinoma cell line SW1990 was exposed to 5-fluorouracil (5-fu) with the concentrations of 1.0 and 10 mug/mL to increase the expression of XIAP. Then 4 RNAi plasmid vectors against XIAP were designed and constructed, then transfected into SW1990. Repressive effect was evaluated by reverse transcriptase polymerase chain reaction and Western blot; 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and flow cytometry were performed to determine cell sensitivity to 5-fu and gemcitabine; furthermore, apoptosis is confirmed by Hoechst 33258 stain.

RESULTS

XIAP of SW1990 can be up-regulated with the chemoresistance increasing 1.5- and 4-fold after 10 and 30 days induced by 5-fu. Two of the 4 vectors can inhibit the expression of XIAP protein more than 60%. The cells apoptosis index induced by 5-fu and gemcitabine increased greatly after XIAP is inhibited by the RNAi plasmid vectors.

CONCLUSIONS

XIAP is one of the most important factors in the pancreatic carcinoma chemoresistance, and inhibition of XIAP in pancreatic carcinoma can enhance the cancer sensitivity to chemotherapeutic drugs.

Targeting XIAP for the treatment of malignancy

X-linked inhibitor of apoptosis protein (XIAP) is a member of the inhibitor of apoptosis proteins family of caspase inhibitors that selectively binds and inhibits caspases-3, -7 and -9, but not caspase-8. As such, XIAP blocks a substantial portion of the apoptosis pathway and is an attractive target for novel therapeutic agents for the treatment of malignancy. Antisense oligonucleotides directed against XIAP are effective in vitro and are currently being evaluated in clinical trials. Small molecule XIAP inhibitors that target the baculovirus IAP repeat (BIR) 2 or BIR 3 domain are in preclinical development and are advancing toward the clinic. This review will discuss the progress being made in developing antisense and small-molecule XIAP inhibitors.

Inhibitors of apoptosis proteins in human cervical cancer

Background

It has been shown that IAPs, in particular XIAP, survivin and c-IAP1, are overexpressed in several malignancies. In the present study we investigate the expression of c-IAP1, c-IAP2, XIAP and survivin and its isoforms in cervical cancer.

Methods

We used semiquantitative RT-PCR assays to analyze 41 cancer and 6 normal tissues. The study included 8 stage I cases; 16 stage II; 17 stageIII; and a control group of 6 samples of normal cervical squamous epithelial tissue.

Results

c-IAP2 and XIAP mRNA levels were similar among the samples, cervical tumors had lower c-IAP1 mRNA levels. Unexpectedly, a clear positive association was found between low levels of XIAP and disease relapse. A log-rank test showed a significant inverse association (p = 0.02) between XIAP expression and tumor aggressiveness, as indicated by disease relapse rates. There were no statistically significant differences in the presence or expression levels of c-IAP1 and c-IAP2 among any of the clinical variables studied. Survivin and its isoforms were undetectable in normal cervical tissues, in contrast with the clear upregulation observed in cancer samples. We found no association between survivin expression and age, clinical stage, histology or menopausal state. Nevertheless, we found that adenocarcinoma tumors expressed higher levels of survivin 2B and DeltaEx3 (p = 0.001 and p = 0.04 respectively, by Kruskal-Wallis). A multivariate Cox's partial likelihood-based analysis showed that only FIGO stage was an independent predictor of outcome.

Conclusion

There are no differences in the expression of c-IAP2 and XIAP between normal vs. cancer samples, but XIAP expression correlate in cervical cancer with relapse of this disease in the patients. Otherwise, c-IAP1 was downregulated in the cervical cancer samples. The expression of survivin was upregulated in the patients with cervical cancer. We have found that adenocarcinoma presented higher levels of survivin isoforms 2B and DeltaEx3.

Expression and localization of inhibitor of apoptosis proteins in normal human tissues

The family of inhibitor of apoptosis (IAP) proteins can suppress apoptosis induced by a variety of triggers. Among the IAPs, cIAP1, cIAP2, and XIAP have been characterized as inhibitors of specific caspases, and their expression, together with that of survivin, has been shown in several studies to play a role as tumor marker and prognostic factor for the survival of patients with cancer. Although survivin is usually not expressed in normal adult tissues, cIAP1, cIAP2, and XIAP have been found broadly expressed at messenger RNA level within normal cells. Here, we report an immunohistochemical study in a comprehensive panel of normal human tissues, and we confirm at the protein level the wide expression of IAPs. These results are consistent with a physiological role of IAPs in normal cells. Moreover, we show that IAPs' expression levels and localization patterns differ depending on the cell lineage. The variable subcellular localization of the IAPs within different cell types suggests that compartmentalization may contribute to regulate their function. The physiological role of these proteins should be further investigated to help tailor IAP-targeted therapeutic strategies for patients with cancer and circumvent possible side effects.

Nuclear expression of cIAP-1, an apoptosis inhibiting protein, predicts lymph node metastasis and poor patient prognosis in head and neck squamous cell carcinomas

cIAP-1, an apoptosis inhibiting protein, has been suggested to play important roles in the development of cervical and esophageal squamous cell carcinomas (SCCs). In order to clarify the subcellular localization of cIAP-1 and to investigate its clinicopathological significance in head and neck SCCs (HNSCCs), we examined cIAP-1 expression in four oral SCC cell lines by immunocytochemistry and Western blot. Expressions of nuclear and cytoplasmic cIAP-1, caspase-3, and Smac/DIABLO were also examined immunohistochemically in 57 cases of the HNSCCs. cIAP-1 expression was detected in HSC-2, HSC-3, and HSC-4 cells by immunohistochemistry and Western blot. In HSC-2 and HSC-4 cells, cIAP-1 was detected in both the nuclear and cytoplasmic fractions. Nuclear cIAP-1 expression was positive in 17 (30%) of HNSCCs, was correlated with lymph node metastasis (P=0.020) and advanced disease stage (P=0.032), and tended to be correlated with poor patient prognosis (P=0.059). Cytoplasmic cIAP-1 expression showed similar but weaker clinicopathological correlations. Nuclear cIAP-1 expression was inversely correlated with caspase-3 expression, but was correlated with Smac/DIABLO expression. Nuclear cIAP-1 expression appears to be a useful marker for predicting poor patient prognosis in HNSCCs, and may play roles in HNSCCs through the signaling pathway mediated by Smac/DIABLO and caspase-3.

Targeting the IAP family of caspase inhibitors as an emerging therapeutic strategy

The IAPs (inhibitor of apoptosis proteins) are a family of caspase inhibitors that block the execution phase of apoptosis. Overexpression of IAPs confers chemoresistance and, in some groups of patients, is associated with a poor prognosis. Given their role in the development and progression of solid tumors and hematologic malignancies, efforts are underway to develop therapeutic IAP inhibitors, with a focus on X-linked IAP (XIAP) and survivin. Antisense oligonucleotides that target XIAP and survivin have been developed and are currently in phase I clinical trial. Small-molecules that bind and inhibit XIAP have also been identified and are in the process of clinical development. This review focuses on the preclinical data that support the development of IAP-targeted therapies.

Apoptotic Pathways and Therapy Resistance in Human Malignancies

Apoptosis and necrosis are two morphologically distinct forms of cell death that are important for maintaining of cellular homeostasis. Almost all agents can provoke either response when applied to cells; however, the duration of treatment and the dose of the used agents determine which type of death (apoptosis or necrosis) is initiated. The response of tumors to chemo-, radio-, and hormone therapy or to treatment with biologically active agents may depend at least in part on the propensity of these tumors to undergo cell death. Some tumors, e.g., leukemias, small cell lung cancer, and seminomas, respond quickly to first-line therapy; this fast response is thought to result from induction of apoptosis. Solid tumors, on the other hand, usually respond slowly and less effectively, with cell death characterized not only by apoptosis but also by necrosis, or mitotic catastrophe. It is likely that resistance of tumors to treatment might be associated with defects in, or dysregulation of, different steps of the apoptotic pathways. Several attempts were undertaken to use the knowledge of these defects to design new drugs, which might either activate or re-activate the apoptotic machinery of tumor cells. Here we discuss the apoptotic pathways and their role in therapy resistance of human malignancies. Although such studies are still in progress, they offer great promise for future cancer therapy. We hope that some of these agents will turn out to be valuable additions to the future therapeutic arsenal, which will most probably include a combination of conventional cytotoxic drugs and molecular target-based pro-apoptotic drugs.

Targeting the IAP Family of Caspase Inhibitors as an Emerging Therapeutic Strategy

The IAPs (inhibitor of apoptosis proteins) are a family of caspase inhibitors that block the execution phase of apoptosis. Overexpression of IAPs confers chemoresistance and, in some groups of patients, is associated with a poor prognosis. Given their role in the development and progression of solid tumors and hematologic malignancies, efforts are underway to develop therapeutic IAP inhibitors, with a focus on X-linked IAP (XIAP) and survivin. Antisense oligonucleotides that target XIAP and survivin have been developed and are currently in phase I clinical trial. Small-molecules that bind and inhibit XIAP have also been identified and are in the process of clinical development. This review focuses on the preclinical data that support the development of IAP-targeted therapies.

p73 expression is associated with the cellular radiosensitivity in cervical cancer after radiotherapy

Apoptosis is one of the causes of cell death in cervical cancer following radiotherapy. By studying the gene expression profile with cDNA apoptotic array, the p73 gene was found overexpressed in radiosensitive cervical cancers when compared with radioresistant ones. To investigate the role of the p73 gene in relation to clinical assessment of radiosensitivity in cervical cancer based on the findings of residual tumor cells in cervical biopsies after completion of radiotherapy, we studied the protein expression of p73 in 59 cervical cancers after radiotherapy and 68 normal cervices using immunohistochemistry. The expression of p73 was found to be significantly increased in cancer samples and, more importantly, in those samples sensitive to radiotherapy (P < 0.001). The overexpression of p73 actually predicted a better prognosis in cervical cancer patients (P < 0.001). To investigate the possible involvement of p73 downstream genes, the protein expressions of p21 and Bax were studied. The expression of p21, but not Bax, was found to be positively correlated with the expression of p73 (P = 0.001). Furthermore, the epigenetic regulation of p73 expression via DNA methylation was also investigated in 103 cervical cancers and 124 normals. Hypermethylation of p73 gene was observed in 38.8% of cervical cancers, and it was significantly associated with reduced or absent p73 expression (P < 0.001). Reactivation of p73 expression in two cervical cancer cell lines by demethylation treatment supported the role of methylation in the regulation of p73 expression. Our findings suggested that p73 expression was related to the radiosensitivity of cervical cancer cells and may play an important role in the regulation of cellular radiosensitivity.

Disturbed balance of expression between XIAP and Smac/DIABLO during tumour progression in renal cell carcinomas

Dysregulation of apoptosis plays an important role in tumour progression and resistance to chemotherapy. The X-linked inhibitor of apoptosis (XIAP) is considered to be the most potent caspase inhibitor of all known inhibitor of apoptosis-family members. Only recently, an antagonist of XIAP has been identified, termed Smac/DIABLO. To explore the relevance of antiapoptotic XIAP and proapoptotic Smac/DIABLO for tumour progression in renal cell carcinomas (RCCs), we analysed XIAP and Smac/DIABLO mRNA and protein expression in the primary tumour tissue from 66 RCCs of all major histological types by quantitative real-time PCR, Western blot and ELISA. X-linked inhibitor of apoptosis and Smac/DIABLO mRNA expression was found in all RCCs. Importantly, the relative XIAP mRNA expression levels significantly increased from early (pT1) to advanced (pT3) tumour stages (P=0.0002) and also with tumour dedifferentiation (P=0.04). Western blot analysis confirmed the tumour stage-dependent increase of XIAP expression on the protein level. In contrast, mRNA and protein expression levels of Smac/DIABLO did not significantly change between early and advanced tumour stages or between low and high tumour grades. Consequently, the mRNA expression ratio between antiapoptotic XIAP and proapoptotic Smac/DIABLO markedly increased during progression from early (pT1) to advanced (pT3) tumour stages. Moreover, RCCs confined within the organ capsule (pT1 and pT2) exhibited a significantly lower XIAP to Smac/DIABLO expression ratio when compared with RCCs infiltrating beyond the kidney (pT3; P=0.01). Thus, our investigation demonstrates that the delicate balance between XIAP and Smac/DIABLO expression is gradually disturbed during progression of RCCs, resulting in a relative increase of antiapoptotic XIAP over proapoptotic Smac/DIABLO, thereby probably contributing to the marked apoptosis resistance of RCC.

Chromosome in situ hybridisation, Ki-67, and telomerase immunocytochemistry in liquid based cervical cytology

AIMS

To assess the potential value of chromosome in situ hybridisation (CISH), Ki-67, and telomerase immunocytochemistry in liquid based cervical cytology to help detect carcinoma cells and precursors.

METHOD

Sixty ThinPrep processed cervical cytology samples were studied: 23 cases within the normal limit, 13 low grade squamous intraepithelial lesions (LSILs), 10 high grade squamous intraepithelial lesions (HSILs), six squamous cell carcinomas, three endocervical adenocarcinomas, two cervical adenosquamous cell carcinomas, and three endometrial adenocarcinomas. CISH was performed with DNA probes specific for the pericentromeric regions of chromosome 11 and 16. Hybridisation signals were visualised with the streptavidin-biotin peroxidase technique. The monoclonal MIB1 and polyclonal TRT-H231 antibodies were used to detect Ki-67 and telomerase immunoreactivity, respectively.

RESULTS

Non-specific background staining was almost absent in CISH slides. Normal squamous and glandular cells showed a diploid chromosomal pattern. A relative gain in chromosomes 11 and 16 (aneusomy) was seen in HSIL and the carcinomas (p<0.0001). In MIB1 stained smears, normal cells and koilocytes showed inconspicuous immunoreactivity, whereas strongly immunoreactive nuclei were found in cancer cells and HSIL (p<0.0001). Not only carcinoma and HSIL cells, but also some normal cells, showed cytoplasmic staining for telomerase.

CONCLUSIONS

These preliminary results indicate that ThinPrep processed cervical smears are suitable for CISH and immunocytochemical studies. The neoplastic squamous and glandular cells were easily identified based on nuclear aneusomy and strong Ki-67 immuoreactivity in the context of abnormal nuclear morphology. This is the first study to apply CISH in cervical cytology using an immunoenzymatic approach.

XIAP expression is an independent prognostic marker in clear-cell renal carcinomas1 1The results of the study are part of the PhD thesis of E. Caliskan

Deregulation of apoptosis plays an important role in carcinogenesis, tumor progression, and resistance to chemotherapy. XIAP is considered to be the most potent caspase inhibitor of all known IAP (inhibitor of apoptosis) family members. To explore the relevance of XIAP for progression and prognosis in renal cell carcinomas (RCCs) of the clear-cell type, we analyzed XIAP protein expression in formalin-fixed tissue from 145 clear-cell RCCs by immunohistochemistry. XIAP protein expression was found in 95% of clear-cell RCCs. A significant increase of XIAP expression became evident from well (G1) to poorly (G3) differentiated clear-cell RCCs (P < 0.0001) and from low (pT1) to advanced (pT3) tumor stages (P = 0.0016). Log-rank test showed a significant inverse correlation (P = 0.0174) between XIAP expression and tumor aggressiveness as indicated by patients' survival. Most important, multivariate Cox regression analysis revealed that XIAP expression is an independent prognostic parameter (P = 0.018) in clear-cell RCCs. Our results suggest an important role for XIAP-mediated inhibition of apoptosis during progression of clear-cell RCCs and introduce XIAP expression as a new independent prognostic marker in this tumor type.