SMAC is expressed de novo in a subset of cervical cancer tumors

Coexpression of Smac/DIABLO and Estrogen Receptor in breast cancer

BACKGROUND

Smac/DIABLO is a proapoptotic protein deregulated in breast cancer, with a controversial role as a tumor marker, possibly due to a lack of correlative mRNA and protein analyses.

OBJECTIVE

To investigate the association of Smac/DIABLO gene and protein levels with clinical variables in breast cancer patients.

METHODS

Smac/DIABLO mRNA expression was analyzed by qPCR in 57 frozen tissues, whereas protein levels were assessed by immunohistochemistry in 82 paraffin-embedded tissues. Survivin mRNA levels were also measured. In vitro assays were performed to investigate possible regulators of Smac/DIABLO.

RESULTS

Higher levels of Smac/DIABLO mRNA and protein were found in estrogen receptor (ER)-positive samples (p= 0.0054 and p= 0.0043, respectively) in comparison to ER-negative tumors. A negligible positive association was found between Smac/DIABLO and survivin expression. In vitro assays showed that Smac/DIABLO is not regulated by ER and, conversely, it does not participate in ER expression modulation.

CONCLUSIONS

mRNA and protein levels of Smac/DIABLO were increased in ER-positive breast tumors in comparison with ER-negative samples, although the mechanism of this regulation is still unknown. Public databases showed a possible clinical relevance for this association.

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.

Putting the pieces together: How is the mitochondrial pathway of apoptosis regulated in cancer and chemotherapy?

In order to solve a jigsaw puzzle, one must first have the complete picture to logically connect the pieces. However, in cancer biology, we are still gaining an understanding of all the signaling pathways that promote tumorigenesis and how these pathways can be pharmacologically manipulated by conventional and targeted therapies. Despite not having complete knowledge of the mechanisms that cause cancer, the signaling networks responsible for cancer are becoming clearer, and this information is serving as a solid foundation for the development of rationally designed therapies. One goal of chemotherapy is to induce cancer cell death through the mitochondrial pathway of apoptosis. Within this review, we present the pathways that govern the cellular decision to undergo apoptosis as three distinct, yet connected puzzle pieces: (1) How do oncogene and tumor suppressor pathways regulate apoptosis upstream of mitochondria? (2) How does the B-cell lymphoma 2 (BCL-2) family influence tumorigenesis and chemotherapeutic responses? (3) How is post-mitochondrial outer membrane permeabilization (MOMP) regulation of cell death relevant in cancer? When these pieces are united, it is possible to appreciate how cancer signaling directly impacts upon the fundamental cellular mechanisms of apoptosis and potentially reveals novel pharmacological targets within these pathways that may enhance chemotherapeutic success.

Array-based gene expression, CGH and tissue data defines a 12q24 gain in neuroblastic tumors with prognostic implication

BACKGROUND

Neuroblastoma has successfully served as a model system for the identification of neuroectoderm-derived oncogenes. However, in spite of various efforts, only a few clinically useful prognostic markers have been found. Here, we present a framework, which integrates DNA, RNA and tissue data to identify and prioritize genetic events that represent clinically relevant new therapeutic targets and prognostic biomarkers for neuroblastoma.

METHODS

A single-gene resolution aCGH profiling was integrated with microarray-based gene expression profiling data to distinguish genetic copy number alterations that were strongly associated with transcriptional changes in two neuroblastoma cell lines. FISH analysis using a hotspot tumor tissue microarray of 37 paraffin-embedded neuroblastoma samples and in silico data mining for gene expression information obtained from previously published studies including up to 445 healthy nervous system samples and 123 neuroblastoma samples were used to evaluate the clinical significance and transcriptional consequences of the detected alterations and to identify subsequently activated gene(s).

RESULTS

In addition to the anticipated high-level amplification and subsequent overexpression of MYCN, MEIS1, CDK4 and MDM2 oncogenes, the aCGH analysis revealed numerous other genetic alterations, including microamplifications at 2p and 12q24.11. Most interestingly, we identified and investigated the clinical relevance of a previously poorly characterized amplicon at 12q24.31. FISH analysis showed low-level gain of 12q24.31 in 14 of 33 (42%) neuroblastomas. Patients with the low-level gain had an intermediate prognosis in comparison to patients with MYCN amplification (poor prognosis) and to those with no MYCN amplification or 12q24.31 gain (good prognosis) (P = 0.001). Using the in silico data mining approach, we identified elevated expression of five genes located at the 12q24.31 amplicon in neuroblastoma (DIABLO, ZCCHC8, RSRC2, KNTC1 and MPHOSPH9). Among these, DIABLO showed the strongest activation suggesting a putative role in neuroblastoma progression.

CONCLUSIONS

The presented systematic and rapid framework, which integrates aCGH, gene expression and tissue data to obtain novel targets and biomarkers for cancer, identified a low-level gain of the 12q24.31 as a potential new biomarker for neuroblastoma progression. Furthermore, results of in silico data mining suggest a new neuroblastoma target gene, DIABLO, within this region, whose functional and therapeutic role remains to be elucidated in follow-up studies.

Survivin and Smac gene expressions but not livin are predictors of prognosis in non-small cell lung cancer patients treated with adjuvant chemotherapy following surgery

OBJECTIVE

Survivin and livin, which are members of the inhibitor of apoptosis protein family, regulate both programmed cell death and proliferation. Second mitochondria-derived activator of caspase is thought to regulate apoptosis by antagonizing inhibitor of apoptosis protein. These gene expressions are regarded as prognostic markers in some malignancies. However, result in previous studies of the association of these gene expressions with prognosis of patients with non-small cell lung cancer remains contradictory.

METHODS

Survivin, livin and second mitochondria-derived activator of caspase mRNA was detected by semi-quantitative reverse transcriptase-polymerase chain reaction in surgical resected tumor specimen from 66 non-small cell lung patients who received adjuvant platinum-based chemotherapy.

RESULTS

Results showed that patients with survivin high expression had significantly shorter tumor-free survival (P = 0.012) and overall survival (P = 0.007) than those with survivin low expression. There was a significant association of second mitochondria-derived activator of caspase high expression in non-small cell lung cancer tissue with longer tumor-free survival (P = 0.021) and overall survival (P = 0.0013). However, livin mRNA expression level had no impact on the tumor-free survival and overall survival of the patients. In multivariate analyses, survivin mRNA high expression (P = 0.033 and P = 0.024) and advanced pathologic stage (P = 0.009 and P = 0.008) were the factors which independently predicted a worse tumor-free survival and overall survival.

CONCLUSIONS

Our data suggest that assessment of survivin and second mitochondria-derived activator of caspase mRNA expression may be useful for predicting survival in non-small cell lung cancer patients receiving platinum-based chemotherapy after surgical resection and can provide valuable information for deciding better therapy strategy.

Role of Smac/DIABLO in cancer progression

Second mitochondria-derived activator of caspase/direct inhibitor of apoptosis-binding protein with low pI (Smac/DIABLO) is a proapoptogenic mitochondrial protein that is released to the cytosol in response to diverse apoptotic stimuli, including commonly used chemotherapeutic drugs. In the cytosol, Smac/DIABLO interacts and antagonizes inhibitors of apoptosis proteins (IAPs), thus allowing the activation of caspases and apoptosis. This activity has prompted the synthesis of peptidomimetics that could potentially be used in cancer therapy. For these reasons, several authors have analyzed the expression levels of Smac/DIABLO in samples of patients from different tumors. Although dissimilar results have been found, a tissue-specific role of this protein emerges from the data. The objective of this review is to present the current knowledge of the Smac/DIABLO role in cancer and its possible use as a marker or therapeutic target for drug design.

The response of human colonocytes to folate deficiency in vitro: functional and proteomic analyses

Low folate intake is associated with colon cancer. We combined a proteomics and biochemical approach to identify proteins and pathways affected by folate deficiency in human colonocytes. Folate differentially altered activity and expression of proteins involved in proliferation [e.g., PCNA], DNA repair [e.g., XRCC5, MSH2], apoptosis [e.g., BAG family chaperone protein, DIABLO and porin], cytoskeletal organization [e.g., actin, ezrin, elfin], and expression of proteins implicated in malignant transformation [COMT, Nit2].

Smac/DIABLO is required for effector caspase activation during apoptosis in human cells

Mitochondria play a pivotal role during stress-induced apoptosis as several proapoptotic proteins are released to the cytosol to activate caspases. Smac/DIABLO is one of the proapoptotic proteins released from the mitochondria and has been shown to inactivate IAPs. However, gene knockout studies in mice revealed a redundant role for Smac during development and cell death. By applying RNA interference-mediated loss of function approach, we demonstrate that Smac/DIABLO is required for the activation of effector but not initiator caspases during stress and receptor-mediated cell death in HeLa cells. Cells with reduced Smac resist apoptosis and retained clonogenicity. Our results suggest an obligatory role for Smac/DIABLO in these tumor cells during several pathways of apoptosis induction.

Apoptosis induced by cAMP requires Smac/DIABLO transcriptional upregulation

Smac/DIABLO is a mitochondrial protein that participates in apoptotic cell death by means of sequestering several members of the inhibitor of apoptosis protein family. This action allows caspase activation, cleavage of key cellular substrates and death. Release from mitochondria is considered the main regulatory step of Smac/DIABLO activity. Nevertheless, the fact that at least one isoform, Smac-beta, does not reside in this organelle implies that transcriptional regulation could also be important. cAMP is a well known second messenger with important apoptotic effects. To analyze if cAMP could be involved in Smac/DIABLO gene regulation, we analyzed 2903 base pairs upstream of the coding sequence and characterized the minimal promoter, which contains a consensus CRE site. We found that cAMP/PKA/CREB pathway is indeed an important regulator of Smac/DIABLO transcription, since exposure to the cAMP analog 8-CPT-cAMP, the adenylyl cyclase activator forskolin, the inhibitor of phosphodiesterase isobutylmethylxanthine or by hindering PKA activation with H89, regulated the promoter activity, as shown by gene reporter and RT-PCR assays. Additionally, the results of site-directed mutagenesis revealed that the consensus CRE site was biologically functional and required for cAMP-induced promoter activity in human HeLa cells. Supporting these results, a negative dominant version of the protein kinase A responsive factor, KCREB, reduced basal Smac/DIABLO expression and rendered the promoter unresponsive to cAMP. Reducing Smac expression using an antisense approach blocked the apoptosis effects of cAMP in cervical cancer cells. These results show that cAMP is an important modulator of the apoptotic threshold in cancer cell by means of regulating Smac/DIABLO expression.

High Smac/DIABLO expression is associated with early local recurrence of cervical cancer

Background

In a recent pilot report, we showed that Smac/DIABLO mRNA is expressed de novo in a subset of cervical cancer patients. We have now expanded this study and analyzed Smac/DIABLO expression in the primary lesions in 109 cervical cancer patients.

Methods

We used immunohistochemistry of formalin-fixed, paraffin-embedded tissue sections to analyze Smac/DIABLO expression in the 109 primary lesions. Seventy-eight samples corresponded to epidermoid cervical cancer and 31 to cervical adenocarcinoma. The median follow up was 46.86 months (range 10–186).

Results

Smac/DIABLO was expressed in more adenocarcinoma samples than squamous tumours (71% vs 50%; p = 0.037). Among the pathological variables, a positive correlation was found between Smac/DIABLO immunoreactivity and microvascular density, a marker for angiogenesis (p = 0.04). Most importantly, Smac/DIABLO immunoreactivity was associated with a higher rate of local recurrence in squamous cell carcinoma (p = 0.002, log rank test). No association was found between Smac/DIABLO and survival rates.

Conclusion

Smac/DIABLO expression is a potential marker for local recurrence in cervical squamous cell carcinoma patients.