The expression of p53-induced protein with death domain (Pidd) and apoptosis in oral squamous cell carcinoma

Lethal and Non-Lethal Functions of Caspases in the DNA Damage Response

Members of the caspase family are well known for their roles in the initiation and execution of cell death. Due to their function in the removal of damaged cells that could otherwise become malignant, caspases are important players in the DNA damage response (DDR), a network of pathways that prevent genomic instability. However, emerging evidence of caspases positively or negatively impacting the accumulation of DNA damage in the absence of cell death demonstrates that caspases play a role in the DDR that is independent of their role in apoptosis. This review highlights the apoptotic and non-apoptotic roles of caspases in the DDR and how they can impact genomic stability and cancer treatment.

Serum Autoantibodies against LRDD, STC1, and FOXA1 as Biomarkers in the Detection of Ovarian Cancer

Purpose

This study is aimed at evaluating serum autoantibodies against four tumor-associated antigens, including LRDD, STC1, FOXA1, and EDNRB, as biomarkers in the immunodiagnosis of ovarian cancer (OC).

Methods

The autoantibodies against LRDD, STC1, FOXA1, and EDNRB were measured using an enzyme-linked immunosorbent assay (ELISA) in 94 OC patients and 94 normal healthy controls (NHC) in the research group. In addition, the diagnostic values of different autoantibodies were validated in another independent validation group, which comprised 136 OC patients, 136 NHC, and 181 patients with benign ovarian diseases (BOD).

Results

In the research group, autoantibodies against LRDD, STC1, and FOXA1 had higher serum titer in OC patients than NHC (P < 0.001). The area under receiver operating characteristic curves (AUCs) of these three autoantibodies were 0.910, 0.879, and 0.817, respectively. In the validation group, they showed AUCs of 0.759, 0.762, and 0.817 and sensitivities of 49.3%, 42.7%, and 48.5%, respectively, at specificity over 90% for discriminating OC patients from NHC. For discriminating OC patients from BOD, they showed AUCs of 0.718, 0.729, and 0.814 and sensitivities of 47.1%, 39.0%, and 51.5%, respectively, at specificity over 90%. The parallel analyses demonstrated that the combination of anti-LRDD and anti-FOXA1 autoantibodies achieved the optimal diagnostic performance with the sensitivity of 58.1% at 87.5% specificity and accuracy of 72.8%. The positive rate of the optimal autoantibody panel improved from 62.4% to 87.1% when combined with CA125 in detecting OC patients.

Conclusion

Serum autoantibodies against LRDD, STC1, and FOXA1 have potential diagnostic values in detecting OC.

Alcohol and Head and Neck Cancer: Updates on the Role of Oxidative Stress, Genetic, Epigenetics, Oral Microbiota, Antioxidants, and Alkylating Agents

Head and neck cancer (HNC) concerns more than 890,000 patients worldwide annually and is associated with the advanced stage at presentation and heavy outcomes. Alcohol drinking, together with tobacco smoking, and human papillomavirus infection are the main recognized risk factors. The tumorigenesis of HNC represents an intricate sequential process that implicates a gradual acquisition of genetic and epigenetics alterations targeting crucial pathways regulating cell growth, motility, and stromal interactions. Tumor microenvironment and growth factors also play a major role in HNC. Alcohol toxicity is caused both directly by ethanol and indirectly by its metabolic products, with the involvement of the oral microbiota and oxidative stress; alcohol might enhance the exposure of epithelial cells to carcinogens, causing epigenetic modifications, DNA damage, and inaccurate DNA repair with the formation of DNA adducts. Long-term markers of alcohol consumption, especially those detected in the hair, may provide crucial information on the real alcohol drinking of HNC patients. Strategies for prevention could include food supplements as polyphenols, and alkylating drugs as therapy that play a key role in HNC management. Indeed, polyphenols throughout their antioxidant and anti-inflammatory actions may counteract or limit the toxic effect of alcohol whereas alkylating agents inhibiting cancer cells' growth could reduce the carcinogenic damage induced by alcohol. Despite the established association between alcohol and HNC, a concerning pattern of alcohol consumption in survivors of HNC has been shown. It is of primary importance to increase the awareness of cancer risks associated with alcohol consumption, both in oncologic patients and the general population, to provide advice for reducing HNC prevalence and complications.

The Role of Caspase-2 in Regulating Cell Fate

Caspase-2 is the most evolutionarily conserved member of the mammalian caspase family and has been implicated in both apoptotic and non-apoptotic signaling pathways, including tumor suppression, cell cycle regulation, and DNA repair. A myriad of signaling molecules is associated with the tight regulation of caspase-2 to mediate multiple cellular processes far beyond apoptotic cell death. This review provides a comprehensive overview of the literature pertaining to possible sophisticated molecular mechanisms underlying the multifaceted process of caspase-2 activation and to highlight its interplay between factors that promote or suppress apoptosis in a complicated regulatory network that determines the fate of a cell from its birth and throughout its life.

Low expression of PIDD is associated with cell proliferation and apoptosis in hepatocellular carcinoma

p53-induced death domain protein (PIDD) facilitates p53-dependent apoptosis through the interaction with components of the death receptor signaling pathways. However, the role of PIDD in hepatocellular carcinoma (HCC) development remains unknown. In this study, we investigated the expression pattern of PIDD in clinical HCC samples and adjacent non-cancerous tissues using immunohistochemistrical and Western blot analyses. The results showed that PIDD was lowly expressed in HCC tissues and HCC cell lines, compared with the adjacent non-tumorous tissues and LO2 normal hepatocytes. In addition, clinicopathological analysis showed that the expression of PIDD was closely related with multiple clinicopathological variables, such as American Joint Committee on Cancer (AJCC) stage, AFP, and poor prognosis of HCC. Univariate and multivariate survival analyses demonstrated that PIDD could serve as an independent prognostic factor to predict the survival of HCC patients. We used serum starvation-refeeding experiment to explore the involvement of PIDD in HCC cell cycle regulation. We found that PIDD was accumulated in growth-arrested HCC cells and was progressively decreased when cells entered into S phase. Moreover, flow cytometry and cell counting kit-8 (CCK-8) assays indicated that depleting the expression of PIDD could facilitate cell cycle progression and accelerate cell proliferation in HepG2 cells, while overexpression of PIDD could result in cell cycle arrest at G1 phase and hinder the cell proliferation in Hep3B cells. Finally, flow cytometry revealed that overexpression of PIDD slightly increased the apoptosis of HCC cells. Taken together, we concluded that PIDD may be a valuable prognostic marker and promising therapeutic target of HCC.

Pingyangmycin stimulates apoptosis in human hemangioma-derived endothelial cells through activation of the p53 pathway

Pingyangmycin (also known as Bleomycin A5) is produced by Streptomyces verticillus var. pingyangensis n.sp., and has anti‑tumor activities against a variety of tumor cells. The aim of the present study was to determine the molecular mechanism(s) underlying the therapeutic effects of pingyangmycin against infantile hemangiomas. Human hemangioma‑derived endothelial cells (HemECs) were treated with pingyangmycin at varying concentrations (100, 200 or 300 µg/ml), and the morphological changes and apoptosis levels were assessed. The gene expression changes were determined by cDNA microarray technology. Transmission electron microscopy examination revealed that the pingyangmycin‑treated HemECs exhibited typical apoptotic characteristics, including chromatin condensation and the formation of apoptotic bodies. Annexin‑V staining demonstrated that pingyangmycin caused a significant and dose‑dependent induction of apoptosis in the HemECs. In the pingyangmycin‑treated HemECs, 4,752 genes demonstrated at least 2‑fold expression changes at the mRNA level. Quantitative polymerase chain reaction confirmed that pingyangmycin significantly upregulated the expression of p53, p53‑induced protein with death domain, Bax, p53 upregulated modulator of apoptosis and p53 inducible gene 3, and downregulated the expression of murine double minute 2. The data demonstrated that the pro‑apoptotic activity of pingyangmycin against infantile hemangiomas involves p53 pathway activation.

PIDDosome-independent tumor suppression by Caspase-2

The PIDDosome, a multiprotein complex constituted of the ‘p53-induced protein with a death domain (PIDD), ‘receptor-interacting protein (RIP)-associated ICH-1/CED-3 homologous protein with a death domain' (RAIDD) and pro-Caspase-2 has been defined as an activating platform for this apoptosis-related protease. PIDD has been implicated in p53-mediated cell death in response to DNA damage but also in DNA repair and nuclear factor kappa-light-chain enhancer (NF-κB) activation upon genotoxic stress, together with RIP-1 kinase and Nemo/IKKγ. As all these cellular responses are critical for tumor suppression and deregulated expression of individual PIDDosome components has been noted in human cancer, we investigated their role in oncogenesis induced by DNA damage or oncogenic stress in gene-ablated mice. We observed that Pidd or Caspase-2 failed to suppress lymphoma formation triggered by γ-irradiation or 3-methylcholanthrene-driven fibrosarcoma development. In contrast, Caspase-2 showed tumor suppressive capacity in response to aberrant c-Myc expression, which did not rely on PIDD, the BH3-only protein Bid (BH3 interacting domain death agonist) or the death receptor ligand Trail (TNF-related apoptosis-inducing ligand), but associated with reduced rates of p53 loss and increased extranodal dissemination of tumor cells. In contrast, Pidd deficiency associated with abnormal M-phase progression and delayed disease onset, indicating that both proteins are differentially engaged upon oncogenic stress triggered by c-Myc, leading to opposing effects on tumor-free survival.

P53-induced protein with a death domain (PIDD): master of puppets?

P53-induced protein with a death domain (PIDD) has been described as primary p53 target gene, induced upon DNA damage. More than 10 years after its discovery, its physiological role in the DNA damage response remains enigmatic, as it seems to be able to execute life-death decisions in vitro, yet genetic ablation in mice failed to reveal an obvious phenotype. Nonetheless, evidence is accumulating that it contributes to the fine-tuning of the DNA-damage response by orchestrating critical processes such as caspase activation or nuclear factor κB translocation and can also exert additional nuclear functions, for example, the modulation of translesion synthesis. In this review, we aim to integrate these observations and propose possible unexplored functions of PIDD.

The PIDDosome, DNA-damage-induced apoptosis and beyond

P53-induced protein with a death domain (PIDD) was cloned as a death domain (DD)-containing protein whose expression is induced by p53. It was later described as the core of a molecular platform-activating caspase-2, named the PIDDosome. These first results pointed towards a role for PIDD in apoptosis, in response to DNA damage. Identification of new PIDDosome complexes involved in DNA repair and nuclear factor-κB signaling challenged this early concept. PIDD functions are growing as new complexes and new interaction partners are being discovered, and as additional functions are being revealed. A fascinating feature of PIDD lies within its complex and tight regulation mechanisms, which allow the molecule to fine-tune its different functions: from transcriptional regulation to the expression of different isoforms, and from the interaction with regulatory proteins to an ingenious post-translational cleavage mechanism generating various active fragments with specific functions. Further studies still need to be carried out to provide answers to many unresolved issues and to reconcile conflicting results. This review aims at providing an overview of the current PIDD knowledge status.

Caspase-2 activation in the absence of PIDDosome formation

PIDD (p53-induced protein with a death domain [DD]), together with the bipartite adapter protein RAIDD (receptor-interacting protein-associated ICH-1/CED-3 homologous protein with a DD), is implicated in the activation of pro–caspase-2 in a high molecular weight complex called the PIDDosome during apoptosis induction after DNA damage. To investigate the role of PIDD in cell death initiation, we generated PIDD-deficient mice. Processing of caspase-2 is readily detected in the absence of PIDDosome formation in primary lymphocytes. Although caspase-2 processing is delayed in simian virus 40–immortalized pidd^−/− mouse embryonic fibroblasts, it still depends on loss of mitochondrial integrity and effector caspase activation. Consistently, apoptosis occurs normally in all cell types analyzed, suggesting alternative biological roles for caspase-2 after DNA damage. Because loss of either PIDD or its adapter molecule RAIDD did not affect subcellular localization, nuclear translocation, or caspase-2 activation in high molecular weight complexes, we suggest that at least one alternative PIDDosome-independent mechanism of caspase-2 activation exists in mammals in response to DNA damage.

The PIDDosome mediates delayed death of hippocampal CA1 neurons after transient global cerebral ischemia in rats

A brief period of global brain ischemia, such as that induced by cardiac arrest or cardiopulmonary bypass surgery, causes cell death in vulnerable hippocampal CA1 pyramidal neurons days after reperfusion. Although numerous factors have been suggested to account for this phenomenon, the mechanisms underlying it are poorly understood. We describe a cell death signal called the PIDDosome, a protein complex of p53-induced protein with a death domain (PIDD), receptor-interacting protein-associated ICH-1/CED-3 homologous protein with a death domain (RAIDD), and procaspase-2. We induced 5 min of transient global cerebral ischemia (tGCI) using bilateral common carotid artery occlusion with hypotension. Western blot analysis showed that expression of twice-cleaved fragment of PIDD (PIDD-CC) increased in the cytosolic fraction of the hippocampal CA1 subregion and preceded procaspase-2 activation after tGCI. Caspase-2 cleaved Bid in brain homogenates. Co-immunoprecipitation and immunofluorescent studies demonstrated that PIDD-CC, RAIDD, and procaspase-2 were co-localized and bound directly, which indicates the formation of the PIDD death domain complex. Furthermore, we tested inhibition of PIDD expression by using small interfering RNA (siRNA) treatment that was initiated 48 h before tGCI. Administration of siRNA against PIDD decreased not only expression of PIDD-CC, but also activation of procaspase-2 and Bid, resulting in a decrease in histological neuronal damage and DNA fragmentation in the hippocampal CA1 subregion after tGCI. These results imply that PIDD plays an important role in procaspase-2 activation and delayed CA1 neuronal death after tGCI. We propose that PIDD is a hypothetical molecular target for therapy against neuronal death after tGCI.