Radiation-induced apoptosis--the ceramide-SAPK signaling pathway and clinical aspects

Identifying hub genes for chemo-radiotherapy sensitivity in cervical cancer: a bi-dataset in silico analysis

PURPOSE

To identify the hub genes that associated with chemo-radiotherapy sensitivity for cervical cancer and to explore the relationship between hub genes and various cellular processes and potential mechanism of cervical cancer.

METHODS

The gene expression data of 21 patients with CESC and the mRNA expression profiles of 296 patients with CESC were obtained from the Gene Expression Omnibus(GEO) and The Cancer Genome Atlas (TCGA) databases, respectively. The potential functions and regulatory mechanisms of differentially expressed genes (DEGs) were identified using GO and KEGG enrichment analyses. Hub genes were identified using random survival forest analysis. The relationship between hub genes and various cellular processes was comprehensively analyzed. The expression of hub genes was assessed using clinical data extracted from the Human Protein Atlas (HPA) database.

RESULTS

A total of 139 and 13 DEGs were found to be upregulated and downregulated, respectively, in CESC. The six hub genes, namely, SELP, PIM2, CCL19, SDS, NRP1, and SF3A2, were significantly correlated with immune cell infiltration, chemotherapy sensitivity, disease-related genes, and enriched signaling pathways (all p-value < 0.05). A nomogram and calibration curve were generated using the six hub genes to predict prognosis with high accuracy. A regulatory network comprising TFs (ZBTB3) and mRNAs (NRP1/PIM2/SELP) and several competitive endogenous RNA (ceRNA) networks comprising mRNAs, miRNAs, and lncRNAs were constructed. Data from HPA indicated that the protein expression of the six hub genes differed significantly between patients with CESC and healthy individuals.

CONCLUSION

Upregulation of SELP, PIM2, CCL19, SDS, NRP1, and SF3A2 is associated with radiotherapy sensitivity and is involved in various cellular processes in CESC. These six genes may serve as biomarkers for predicting the radiotherapy response and prognosis in patients with CESC.

Lipid Metabolism and Cancer

Lipid metabolism is involved in the regulation of numerous cellular processes, such as cell growth, proliferation, differentiation, survival, apoptosis, inflammation, movement, membrane homeostasis, chemotherapy response, and drug resistance. Reprogramming of lipid metabolism is a typical feature of malignant tumors. In a variety of cancers, fat uptake, storage and fat production are up-regulated, which in turn promotes the rapid growth, invasion, and migration of tumors. This paper systematically summarizes the key signal transduction pathways and molecules of lipid metabolism regulating tumors, and the role of lipid metabolism in programmed cell death. In conclusion, understanding the potential molecular mechanism of lipid metabolism and the functions of different lipid molecules may facilitate elucidating the mechanisms underlying the occurrence of cancer in order to discover new potential targets for the development of effective antitumor drugs.

Key radioresistance regulation models and marker genes identified by integrated transcriptome analysis in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignancy that is endemic to China and Southeast Asia. Radiotherapy is the usual treatment, however, radioresistance remains a major reason for failure. This study aimed to find key radioresistance regulation models and marker genes of NPC and clarify the mechanism of NPC radioresistance by RNA sequencing and bioinformatics analysis of the differences in gene expression profiles between radioresistant and radiosensitive NPC tissues. A total of 21 NPC biopsy specimens with different radiosensitivity were analyzed by RNA sequencing. Differentially expressed genes in RNA sequencing data were identified using R software. The differentially expressed gene data derived from RNA sequencing as well as prior knowledge in the form of pathway databases were integrated to find sub‐networks of related genes. The data of RNA sequencing with the GSE48501 data from the GEO database were combined to further search for more reliable genes associated with radioresistance of NPC. Survival analyses using the Kaplan–Meier method based on the expression of the genes were conducted to facilitate the understanding of the clinical significance of the differentially expressed genes. RT‐qPCR was performed to validate the expression levels of the differentially expressed genes. We identified 1182 differentially expressed genes between radioresistant and radiosensitive NPC tissue samples. Compared to the radiosensitive group, 22 genes were significantly upregulated and 1160 genes were downregulated in the radioresistant group. In addition, 10 major NPC radiation resistance network models were identified through integration analysis with known NPC radiation resistance‐associated genes and mechanisms. Furthermore, we identified three core genes, DOCK4, MCM9, and POPDC3 among 12 common downregulated genes in the two datasets, which were validated by RT‐qPCR. The findings of this study provide new clues for clarifying the mechanism of NPC radioresistance, and further experimental studies of these core genes are warranted.

Radical Hemithoracic Radiotherapy Induces Systemic Metabolomics Changes That Are Associated with the Clinical Outcome of Malignant Pleural Mesothelioma Patients

Simple Summary

Radical hemithoracic radiotherapy represents a promising new advance in the field of radiation oncology and encouraging results have been achieved in the treatment of malignant pleural mesothelioma patients. This study showed that this radiotherapy modality produces significant changes in serum metabolomics profile mainly affecting arginine and polyamine biosynthesis pathways. Interestingly, individual metabolomics alterations were found associated with the clinical overall survival outcome of the radiotherapy treatment. These results highlight metabolomics profile analysis as a powerful prognostic tool useful to better understand the mechanisms underlying the interpatients variability and to identify patients who may receive the best benefit from this specific radiotherapy treatment.

Abstract

Radical hemithoracic radiotherapy (RHRT) represents an advanced therapeutic option able to improve overall survival of malignant pleural mesothelioma patients. This study aims to investigate the systemic effects of this radiotherapy modality on the serum metabolome and their potential implications in determining the individual clinical outcome. Nineteen patients undergoing RHRT at the dose of 50 Gy in 25 fractions were enrolled. Serum targeted metabolomics profiles were investigated at baseline and the end of radiotherapy by liquid chromatography and tandem mass spectrometry. Univariate and multivariate OPLS-DA analyses were applied to study the serum metabolomics changes induced by RHRT while PLS regression analysis to evaluate the association between such changes and overall survival. RHRT was found to affect almost all investigated metabolites classes, in particular, the amino acids citrulline and taurine, the C14, C18:1 and C18:2 acyl-carnitines as well as the unsaturated long chain phosphatidylcholines PC ae 42:5, PC ae 44:5 and PC ae 44:6 were significantly decreased. The enrichment analysis showed arginine metabolism and the polyamine biosynthesis as the most perturbed pathways. Moreover, specific metabolic changes encompassing the amino acids and acyl-carnitines resulted in association with the clinical outcome accounting for about 60% of the interpatients overall survival variability. This study highlighted that RHRT can induce profound systemic metabolic effects some of which may have a significant prognostic value. The integration of metabolomics in the clinical assessment of the malignant pleural mesothelioma could be useful to better identify the patients who can achieve the best benefit from the RHRT treatment.

Prediction of neonatal acne based on maternal lipidomic profiling

BACKGROUND

Neonatal acne occurs in the first few weeks after birth. Some lesions are more serious and leave scars. Maternal surface skin lipids (SSL) have a strong correlation with SSL of infants. The establishment of prediction rank model based on maternal SSL is essential to the prevention and treatment of neonatal acne.

METHOD

Surface skin lipids samples were collected from the mothers (M) of 56 neonatal acne patients and the mothers (HM) of 19 healthy infants. Surface skin lipids from the right forehead were collected using a noninvasive method. UPLC-QTOF-MS was applied to detect SSL. Partial least squares discriminant analysis and receiver operating characteristic (ROC) analysis were performed to screen and validate potential lipids. Random forest (RF) and ROC analysis were used to establish a prediction model and evaluate its accuracy.

RESULTS

Sixteen altered potential lipids belonging to fatty acids, sphingomyelins, and glycerides were associated with M. M had less lipids than HM. Spearman's correlation of 16 lipids revealed 9 with high correlation. They were chosen as characteristic values of the RF prediction model. And the model showed an average accuracy of 98% in the validation set.

CONCLUSION

We have established an RF model for predicting neonatal acne and have shown that high skin barrier-related lipids were markers for predicting neonatal acne.

Side Effects in Cancer Therapy: Are Sphingolipids to Blame?

Cancer patients' quality of life is greatly dependent on the efficacy of treatments and their associated side effects, which can significantly reduce the overall quality of life. Although the effectiveness of cancer treatments has improved over time, adverse effects persist with each treatment. Some side effects, such as paclitaxel-induced peripheral neuropathy, can be dose limiting, thus further reducing the potential of paclitaxel chemotherapy treatment. Premature ovarian failure in young female patients due to radiation and chemotherapy therapy can have devastating infertility consequences. In recent years, a class of lipids known as sphingolipids has been identified as playing a role in the side effects of cancer therapies. Advanced analytical technologies, such as mass spectrometry, have provided great aid in detecting and distinguishing individual sphingolipids at low concentrations. Sphingolipids play an important role in cell proliferation and apoptosis and, importantly, sphingolipid metabolism has been shown to be dysregulated in cancer. The goal of this review is to summarize the latest findings of the role of sphingolipids in the injurious side effects in various cancer treatments. A better understanding of the molecular mechanisms driving these sphingolipid-induced side effects can help develop new drugs and treatments for cancer that have fewer side effects, thus improving treatment efficacy and quality of life.

Endocannabinoid and ceramide levels are altered in patients with colorectal cancer

Endocannabinoids and ceramides have demonstrated growth inhibition, cell death induction and pro-apoptotic activity in cancer research. In the present study, we describe the profiles of two major endocannabinoids, ceramides, free fatty acids and relevant metabolic enzymes in 47 pairs of human colorectal cancer tissues and adjacent non-tumor tissues. Among them, anandamide (AEA) and its metabolite, arachidonic acid (AA), were markedly upregulated in cancer tissues particularly in those with lymphatic metastasis. The levels of C16 and C24 ceramides were significantly elevated in the colorectal tumor tissues, while levels of C18 and C20 ceramides showed opposite trends. Levels of two enzymes participating in the biosynthesis and degradation of AEA, N-acyl-phosphatidylethanolamine-hydrolyzing phospholipase D (NPLD) and fatty acid amide hydrolase (FAAH), together with the most abundant ceramide synthases (CerS1, CerS2, CerS5 and CerS6) in the colon were also determined. Quantitative-PCR analysis indicated that the mRNA levels of these enzymes were overexpressed in the tumor tissues. The activities of NPLD and FAAH were also upregulated. In addition, both gene and protein expression levels of cannabinoid receptor 1 (CB1) were elevated but not of CB2. Elevation of AEA and alteration of ceramides (C16, C24, C18, C20) may qualify as potential endogenous biomarkers and novel drug targets for colorectal cancer.

Sphingosine 1-phosphate promotes activation of aprine preantral follicle in vitro

This study describes the effect of sphingosine 1-phosphate (S1P) for development of preantral follicle, therefore the activation and follicular viability of caprine follicles cultured in vitro. Ovarian fragments were cultured for 1 or 7 days in Minimum Essential Medium with different S1P concentrations (0, 1, 10, 50, 100 or 200ng/mL). All ovarian fragments were processed for histological analysis in optical microscopy, transmission electron microscopy and fluorescence analysis. The treatment using 1ng/mL of S1P was able to maintain the percentage of normal follicles with the progression of the culture from day 1 to 7. At end of the 7-day culture period there was a significant reduction (P<0.05) in the percentage of primordial follicles in all groups treated with S1P, compared with fresh control (FC) and Control Culture (CC), which was followed by an increase of activated follicles (intermediary, primary and secondary). In addition, the culture for 7 days with media supplemented with S1P with 1ng/mL preserved the ultrastructure of organelles and kept the preantral follicular viability when evaluated by fluorescence microscopy. In conclusion, after 7 days of culture, the 1ng/mL of S1P activates the development of preantral caprine follicles, cultured in situ and maintains the oocitary and follicular viability.

Combinatorial therapies improve the therapeutic efficacy of nanoliposomal ceramide for pancreatic cancer

Poor prognosis cancers, such as pancreatic cancer, represent inherent challenges for ceramide-based nanotherapeutics due to metabolic pathways, which neutralize ceramide to less toxic or pro-oncogenic metabolites. We have recently developed a novel 80 nanometer diameter liposomal formulation that incorporates 30 molar percent C6-ceramide, a bioactive lipid that is pro-apoptotic to many cancer cells, but not to normal cells. In this manuscript, we evaluated the efficacy of combining nanoliposomal C6-ceramide (Lip-C6) with either gemcitabine or an inhibitor of glucosylceramide synthase. We first assessed the biological effect of Lip-C6 in PANC-1 cells, a gemcitabine-resistant human pancreatic cancer cell line, and found that low doses alone did not induce cell toxicity. However, cytotoxicity was achieved by combining Lip-C6 with either non-toxic sub-therapeutic concentrations of gemcitabine or with the glucosylceramide synthase inhibitor D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP). Furthermore, these combinations with Lip-C6 cooperatively inhibited PANC-1 tumor growth in vivo. Mechanistically, Lip-C6 inhibited pro-survival Akt and Erk signaling, whereas the nucleoside analog gemcitabine did not. Furthermore, by including PDMP within the nanoliposomes, which halted ceramide neutralization as evidenced by LC-MS3, the cytotoxic effects of Lip-C6 were enhanced. Collectively, we have demonstrated that nanoliposomal ceramide can be an effective anti-pancreatic cancer therapeutic in combination with gemcitabine or an inhibitor of ceramide neutralization.

Targeting sphingolipid metabolism in head and neck cancer: rational therapeutic potentials

IMPORTANCE OF THE FIELD

Ceramide accumulation has been shown to be a conserved mechanism of apoptosis initiation in normal physiological processes as well as in response to cancer treatments. Therefore, it is unsurprising that many cancers develop aberrations of sphingolipid metabolism that prevent the accumulation of ceramide, whether by reduction of ceramide generation or by enhanced ceramide catabolism, particularly dangerous when catabolism leads to generation of pro-tumor sphingosine-1-phosphate and ceramide-1-phosphate. Numerous studies have now implicated dysregulation of sphingolipid metabolism in head and neck cancers.

AREAS COVERED IN THIS REVIEW

This review highlights the importance of sphingolipid metabolism and brings sphingolipid metabolism to the forefront in the investigation of novel therapies for head and neck cancer. It reviews sphingolipid-centric therapies under investigation in preclinical and clinical trials of cancers of the head and neck.

WHAT THE READER WILL GAIN

The roles of sphingolipids and sphingolipid metabolism in cancer are reviewed and the reader will be brought up to date with discoveries in the field of sphingolipid metabolism in head and neck cancer.

TAKE HOME MESSAGE

As treatments for head and neck cancers are currently limited, the potential of targeting sphingolipid metabolism should be taken into consideration as we seek novel ways to combat this group of tumors.

Acid ceramidase upregulation in prostate cancer: role in tumor development and implications for therapy

Bioactive sphingolipids, such as ceramide, sphingosine and sphingosine-1-phosphate are known bio-effector molecules which play important roles in various aspects of cancer biology including cell proliferation, growth arrest, apoptosis, metastasis, senescence and inflammation. Therefore, enzymes involved in ceramide metabolism are gaining recognition as being critical regulators of cancer cell growth and/or survival. We previously observed that the ceramide metabolizing enzyme, acid ceramidase (AC) is upregulated in tumor tissues. Studies have now concluded that this creates a dysfunctional ceramide pathway, which is responsible for tumor progression and resistance to chemotherapy and radiation. This suggests that development of small-molecule drugs that inhibit AC enzyme activity is a promising approach for improving standard cancer therapy and patient's clinical outcomes.

Oxidative stress as a significant factor for development of an adaptive response in irradiated and nonirradiated human lymphocytes after inducing the bystander effect by low-dose X-radiation

X-radiation (10cGy) was shown to induce in human lymphocytes transposition of homologous chromosomes loci from the membrane towards the centre of the nucleus and activation of the chromosomal nucleolus-forming regions (NFRs). These effects are transmitted by means of extracellular DNA (ecDNA) fragments to nonirradiated cells (the so-called bystander effect, BE). We demonstrated that in the development of the BE an important role is played by oxidative stress (which is brought about by low radiation doses and ecDNA fragments of the culture medium of the irradiated cells), by an enzyme of apoptosis called caspase-3, and by DNA-binding receptors of the bystander cells, presumably TLR9. Proposed herein is a scheme of the development of an adaptive response and the BE on exposure to radiation. Ionizing radiation induces apoptosis of the radiosensitive fraction of cells due to the development of the "primary" oxidative stress (OS). DNA fragments of apoptotic cells are released into the intercellular space and interact with the DNA-binding receptors of the bystander cells. This interaction activates in lymphocytes signalling pathways associated with synthesis of the reactive oxygen species and nitrogen species, i.e., induces secondary oxidative stress accompanied by apoptosis of part of the cells, etc. Hence, single exposure to radiation may be followed by relatively long-lasting in the cellular population oxidative stress contributing to the development of an adaptive response. We thus believe that ecDNA of irradiated apoptotic lymphocytes is a significant factor of stress-signalling.

Clinical biomarkers and imaging for radiotherapy-induced cell death

INTRODUCTION

Radiotherapy, like most anticancer treatments, achieves its therapeutic effect by inducing different types of cell death in tumors.

CELL DEATH MARKERS AND IMAGING MODALITIES

To evaluate treatment efficacy a variety of routine anatomical imaging modalities is used. However, changes in tumor physiology, metabolism and proliferation often precede these volumetric changes. Therefore, reliable biomarkers and imaging modalities that could assess treatment response more rapidly or even predict tumor responsiveness to treatment in an early phase would be very useful to identify responders and/or avoid ineffective, toxic therapies. A better understanding of cell death mechanisms following irradiation is essential for the development of such tools.

CELL DEATH AND AVAILABLE ASSAYS

In this review the most prominent types of radiation-induced cell death are discussed. In addition, the currently available assays to detect apoptosis, necrosis, mitotic catastrophe, autophagy and senescence in vitro and, if applicable, in vivo, are presented.

Prognostic significance of 99mTc Hynic-rh-annexin V scintigraphy during platinum-based chemotherapy in advanced lung cancer

PURPOSE

The purpose of this study was to evaluate if sequential 99mTc Hynic-rh- annexin V scintigraphy (TAS) can predict outcome in patients with advanced lung cancer, shortly after the start of platinum-based chemotherapy.

PATIENTS AND METHODS

In 16 consecutive chemotherapy-naive patients with advanced stage non-small-cell lung cancer scheduled for platinum-based chemotherapy, TAS was performed before and within 48 hours after the start of therapy. Chemotherapy-induced changes in tumor annexin V uptake, calculated as maximum count per pixel and expressed as percentage to baseline value, were compared with treatment response determined according to Response Evaluation Criteria in Solid Tumors.

RESULTS

A significant correlation (r2 = 0.86; P = .0001) was found between annexin V metabolic changes and treatment outcome. All patients with notably increased annexin V tumor uptake showed complete or partial response. Less prominently increased or decreased uptake correlated with stable or progressive disease.

CONCLUSION

TAS is a promising test to predict tumor response in patients with advanced lung cancer early in the course of platinum-based chemotherapy.

Sphingosine 1-phosphate protects ovaries from chemotherapy-induced damage in vivo

OBJECTIVE

To investigate whether sphingosine-1-phosphate (S1P), an apoptosis-inhibitor, would be able to protect ovarian follicles from chemotherapy-induced cell death in vivo.

DESIGN

Animal study.

SETTING

Academic medical center.

ANIMAL(S)

Twenty female mice.

INTERVENTION(S)

Twenty mice were randomly assigned into three groups: in group A (n = 8), each mouse received an injection of low concentration of S1P (A1: 0.5 mM), prepared in a vehicle (PET) into the bursa of one ovary and a high concentration (A2: 2.0 mM S1P) to the contralateral ovary. In group B (n = 8), only PET was injected to both ovaries. Afterwards, both groups received 100 mug Dacarbazine (Medac, Hamburg, Germany) IV. The control group C (n = 4) received no chemotherapy. After 2 weeks, the ovaries from group C and from 4 mice from group A and B were evaluated histologically. The remaining mice from group A and B were allowed 3 mating attempts at 4, 8, and 12 weeks after chemotherapy.

MAIN OUTCOME MEASURE(S)

Primordial/primary and pre-/antral follicular density, pregnancy rates.

RESULTS

Chemotherapy caused a significant reduction in the mean number of primordial follicles of mice treated with only PET or with low concentration of S1P (1.86/field of view [C] vs. 1.17 [B] and 0.98 [A1]; P=.006 and P<.0001, respectively) but not in the ovaries treated with high concentration of S1P (2.05/field of view [A2]; P=.918, not significant). Furthermore, three mice (75%) from group A became pregnant at the first mating attempt, in contrast to group B, in which only one mouse (25%) became pregnant and only after the third mating attempt.

CONCLUSION(S)

Local application of S1P protects ovarian follicles from chemotherapy-induced cell death, thereby preserving fertility.

Effects of ceramide inhibition on experimental radiation-induced oral mucositis

OBJECTIVE

Oral mucositis (OM) is a common toxicity of ionizing radiation (IR), which is used as treatment for head and neck cancer. Ceramide-mediated apoptosis may contribute to the pathogenesis of mucositis. In response to IR or other cellular stresses, ceramide production occurs either by the hydrolytic action of sphingomyelinase (SMase) or de novo via ceramide synthase.

STUDY DESIGN

Male golden Syrian hamsters (10 per group) exposed to a single dose of 40 Gy ionizing radiation (day 0) were treated with subcutaneous 0.2 mL injections of either neutral SMase, acidic SMase, or ceramide synthase inhibitor (5 mmol/L glutathione, 5 micromol/L desipramine, or 1 micromol/L fumonisin B1, respectively) from day -1 to day 16. A control group was treated with saline. Two blinded examiners assessed clinical OM development from day 6 to day 26. Two animals per group were killed on days 3, 10, and 16 for immunohistochemical detection of ceramide expression in both the epithelium and in the connective tissue.

RESULTS

The group exposed to fumonisin B1 exhibited a statistically significant reduction in mean daily weight gain, mean mucositis score, duration of mucositis, and expression of ceramide in the epithelium on day 3 as well as in the connective tissue on days 10 and 16 relative to control. Immunohistologic analysis also revealed significant differences in ceramide expression on days 3 and 16 for animals treated with glutathione in both the epithelial and connective tissue when compared to the control.

CONCLUSIONS

These results suggest that IR triggers early de novo ceramide production and that inhibition of this process attenuates OM on a clinical level.

Sphingosine 1-Phosphate Protects Bovine Oocytes from Heat Shock During Maturation1

Sphingosine 1-phosphate (S1P) is a sphingolipid metabolite that can block apoptosis by counteracting the proapoptotic effects of ceramide. Experiments were performed to evaluate whether S1P blocks the disruption in oocyte developmental competence caused by heat shock. Cumulus-oocyte complexes (COCs) were placed in maturation medium and cultured at 38.5 or 41 degrees C for the first 12 h of maturation. Incubation during the last 10 h of maturation, fertilization, and embryonic development were performed at 38.5 degrees C. Heat shock during the first 12 h of maturation reduced cleavage rate, the number of oocytes developing to the blastocyst stage, and the percentage of cleaved embryo that subsequently developed to blastocysts. Addition of 50 nM S1P to maturation medium had no effect on oocytes matured at 38.5 degrees C but blocked effects of thermal stress on cleavage and subsequent development. The blastocysts formed at Day 8 did not differ between S1P and control groups in caspase activity, total cell number, or percentage of cells that were apoptotic. Blocking endogenous generation of S1P by addition of 50 nM N1N-dimethylsphingosine, a sphingosine kinase inhibitor, reduced or tended to reduce cleavage rate and blastocyst development regardless of whether maturation of COCs was at 38.5 or 41 degrees C. Results demonstrate that S1P protects oocytes from a physiologically relevant heat shock and affects oocyte maturation even in the absence of heat shock. The S1P-treated oocytes that survived heat shock and became blastocysts had a normal developmental potential as determined by caspase activity, total cell number, and percentage of apoptotic cells. Thus, modulation of developmental competence of oocytes using S1P may be a useful approach for enhancing fertility in situations where developmental competence of oocytes is compromised.

Ceramide analogues in apoptosis: a new strategy for anticancer drug development

A survey on the role played by ceramide within the sphingolmyelin pathway is here reported, taking into account its importance as an intracellular effector molecule in apoptosis. Recently, several analogs of ceramide, able to pass the cell membrane and then to induce apoptosis, have been developed as a new potential approach in anticancer therapy.

Increasing endogenous ceramide using inhibitors of sphingolipid metabolism maximizes ionizing radiation-induced mitochondrial injury and apoptotic cell killing

To enhance the killing effects of ionizing radiation, we amplified the endogenous ceramide signal in Jurkat cell cultures using 3 different inhibitors of sphingolipid metabolism: DL-PDMP, D-MAPP and imipramine. Of the various possible drug combinations, only DL-PDMP (20 microM) + imipramine (20 microM) and DL-PDMP (20 microM) + imipramine (20 microM) + D-MAPP (5 microM) induced a major increase in ceramide levels, reaching 240% and 340% of control values, respectively, after incubation for 48 hr. With these models, we demonstrate that endogenously formed ceramide triggers time- and concentration-dependent apoptosis through induction of mitochondrial injury and activation of the caspase pathway. Cellular dysfunction includes alterations to the cellular redox potential, as assessed by the generation of ROS and total glutathione depletion, and a drop in Delta Psi(m). A parallel elevation of mitochondrial ceramide levels was also observed. The combination of DL-PDMP + imipramine +/- D-MAPP with 10 Gy irradiation produced cumulative effects leading to apoptosis via mitochondrial collapse and activation of the caspase cascade. The association efficiency was confirmed in normal and acid sphingomyelinase-deficient lymphoid cell lines. Taken together, these results suggest that increasing endogenous ceramide levels may potentially be very valuable when combined with ionizing radiation in tumor therapy.

Novel techniques in the delivery of radiation in pediatric oncology

The field of radiation oncology continues to develop at a rapid pace, due to concurrent progress in high speed computing, improved sensitivity in diagnostic imaging (both anatomic and physiologic), and the introduction of rational new therapeutics built on solid radiobiologic principles. These innovations will become critically important in the field of pediatric oncology, as they will allow for an increased therapeutic ratio in the developing child. Maximizing the benefit of lower dose radiation through the use of radiation modifiers (hypoxic cell sensitizers, signal transduction pathway inhibitors, concurrent chemotherapy), increasing the tolerance of normal tissues (radioprotectors) and tailoring the target area more closely to the desired critical tissues (IMRT, functional simulation with PET and MRS, radiolabeled monoclonal antibodies) will lessen the short and long term toxicity of radiation and increase its effectiveness.

Flow cytometric detection of apoptotic bone marrow cells with fractional DNA content after application of WR-2721, cyclophosphamide, cisplatin, and exposure of mice to gamma rays

Little is known about the mechanisms of apoptosis triggered in normal cells of the haemopoietic system by the aminothiol WR-2721 (Amifostine), chemotherapeutic drugs, and ionizing radiation; thus, the present study was undertaken to evaluate the effects of WR-2721, cyclophosphamide (CP), cisplatin (CDDP), and 60Co gamma rays on induction of apoptotic DNA degradation in bone marrow cells. Adult male Swiss mice were treated with WR-2721 (400 mg/kg b.wt.), CP (200 mg/kg b.wt.), and CDDP (10 mg/kg b.wt.), and exposed to 6 Gy 60Co gamma rays. Alterations in the number of apoptotic cells with fractional DNA content and also the cell cycle position of the non-apoptotic cells were determined in the bone marrow at 7 and 24 hours after treatment of mice with these agents, using flow cytometric assay of the controlled extraction of low-MW DNA from apoptotic cells. The chemotherapeutic drugs CP and CDDP and 60Co gamma rays triggered apoptosis and affected the cell cycle position of the non-apoptotic cells in the mouse bone marrow. The pretreatment of mice with WR-2721 resulted in the modulatory action of the aminothiol on induction of apoptotic cell death and changes in the cell cycle distribution of the non-apoptotic cells caused by the DNA-damaging agents. The patterns of changes in the frequency of apoptotic cells and the cell cycle position of the non-apoptotic cells, observed in the bone marrow, were dependent on the agent(s) applied and the time interval after application of the drug(s) and exposure of mice to gamma rays. Understanding of the mechanisms responsible for triggering of apoptotic cell death and disturbing of the cell cycle by the DNA-damaging agents, and modulation of the apoptotic and cell cycle pathways by the aminothiol WR-2721, can lead to more effective therapy and chemo- and radio-protection of normal cells.

Apoptosis as a cellular predictor for histopathologic response to neoadjuvant radiochemotherapy in patients with rectal cancer

BACKGROUND

Tumor shrinkage by preoperative radiochemotherapy (RCT) can markedly improve surgery in locally advanced (T4) rectal cancer with clear resection margins and may enable sphincter preservation in low-lying tumors. However, tumor response varies considerably, even among tumors treated according to the same protocol. If one is able to identify patients with highly radio-responsive tumors at the time of diagnosis, a selective and individualized policy of preoperative RCT might be pursued.

METHODS

The apoptotic index (AI), Ki-67, p53, and bcl-2 were evaluated by immunohistochemistry on pretreatment biopsies from 44 patients treated uniformly according to a prospective neoadjuvant RCT protocol (CAO/AIO/ARO-94). Treatment response was assessed histopathologically in the resected surgical specimen, using a five-point grading system. Expression of each marker was correlated with tumor response and relapse-free survival after curative surgery.

RESULTS

Tumors with complete (n = 3) or good (n = 28) response to RCT showed significantly higher pretreatment levels of apoptosis (mean AI: 2.06%) than tumors with moderate (n = 7), minimal (n = 5), or no regression (n = 1) from RCT (AI: 1.44%, p = 0.003). The AI was significantly related to Ki-67 (p = 0.05), but not to p53 and bcl-2 status. Tumor regression and AI best predicted relapse-free survival after combined modality treatment and curative surgery.

CONCLUSION

Spontaneous apoptosis in rectal cancer may serve as an important predictor of tumor regression from RCT in rectal cancer and as a significant prognosticator of relapse-free survival. Thus, this molecular marker may finally help to tailor therapy with regard to (neo-) adjuvant treatment of rectal cancer.

Prognostic factors in transitional cell cancer of the bladder: an emerging role for Bcl-2 and p53

BACKGROUND AND PURPOSE

In a recent study on patients with transitional cell cancer of the bladder treated with curative radiotherapy following TUR-T, we demonstrated that a low apoptotic index and p53 positivity were associated with poor local control. The purpose of this study was to assess the prognostic significance of additional markers implicated in regulation of cell cycle and apoptosis.

PATIENTS AND METHODS

Bcl-2, Bax and p21 positivity were detected immunohistochemically on paraffin-embedded pre-treatment biopsies from 83 patients with invasive transitional cell cancer (TCC) of the bladder, treated with radiotherapy. In addition, markers determined in an earlier analysis, i.e.: p53, apoptotic index, cyclin D1, retinoblastoma protein and Ki-67 were included in the multivariate analysis. A stepwise proportional hazard analysis was performed, adjusting for classic prognostic factors (T-stage, grade, multifocality and macroscopic completeness of the TUR). Positivity was defined as >10% of tumor cells staining positive for Bcl-2, Bax and p21, and >20% for p53.

RESULTS

Bcl-2 positivity was found in 63%, Bax was positive in 52% and p21 in 55% of cases. In the PH analysis Bcl-2 positivity was found to be related to poor local control (36 vs. 72% at 3 years; P=0.003), as well as to shorter disease-specific survival (74 vs. 94% at 3 years; P=0.017). Evidence for an adverse effect of p53 positivity was also found (local control: 32 vs. 69% at 3 years;P=0.037, disease-specific survival: 76 vs. 92% at 3 years; P=0.043). In an additional PH analysis, we found poor local control rates for bladder cancers with combined Bcl-2 and p53 positivity (17 vs. 65% at 3 years; P=0.0017), and lower disease specific survival (60 vs. 92%; P=0.0024), disease-free survival (7 vs.35%, P=0.0023) and overall survival (39 vs. 80%; P=0.0018).

CONCLUSION

This study provides evidence for a poor outcome in patients treated with radiotherapy for TCC of the bladder expressing both Bcl-2 and p53. This relationship was found for local control and disease-free, disease-specific and overall survival.

The p75 neurotrophin receptor activates Akt (protein kinase B) through a phosphatidylinositol 3-kinase-dependent pathway

The Akt kinase plays a crucial role in supporting Trk-dependent cell survival, whereas the p75 neurotrophin receptor (p75NTR) facilitates cellular apoptosis. The precise mechanism that p75NTR uses to promote cell death is not certain, but one possibility is that p75NTR-dependent ceramide accumulation inhibits phosphatidylinositol 3-kinase-mediated Akt activation. To test this hypothesis, we developed a system for examining p75NTR-dependent apoptosis and determined the effect of p75NTR on Akt activation. Surprisingly, p75NTR increased, rather than decreased, Akt phosphorylation in a variety of cell types, including human Niemann-Pick fibroblasts, which lack acidic sphingomyelinase activity. The p75NTR expression level required to elicit Akt phosphorylation was much lower than that required to activate the JNK pathway or to mediate apoptosis. We show that p75NTR-dependent Akt phosphorylation was independent of TrkA signaling, required active phosphatidylinositol 3-kinase, and was associated with increased tyrosine phosphorylation of p85 and Shc and with reduced cytosolic tyrosine phosphatase activity. Finally, we show that p75NTR expression increased survival in cells exposed to staurosporine or subjected to serum withdrawal. These findings indicate that p75NTR facilitates cell survival through novel signaling cascades that result in Akt activation.

Radiotherapy and cellular signalling

Developments in cellular and molecular biology in the past decade have increased our understanding of the processes by which cells respond to ionising radiation. Cells use complex protein signalling systems that recognise radiation damage to DNA and plasma membrane lipids. When damage is found, it leads to the activation of various intracellular pathways that modulate the activity of genes controlling ceflular responses such as apoptosis, cell-cycle arrest, or repair. Numerous molecular targets may be activated or inhibited in an attempt to upregulatre or downregulate the radiation response. In this review, we discuss some of the new compounds and techniques for manipulating the cell's response to radiation.

Apoptosis in rectal carcinoma: prognosis and recurrence after preoperative radiotherapy

BACKGROUND

Rectal carcinoma is common, with considerable local recurrence and death rates. Preoperative radiotherapy and refined surgical techniques can improve local control. The aim of this study was to investigate the interaction between apoptosis and the outcome of rectal carcinoma, with and without short-term preoperative radiotherapy.

METHODS

Specimens were from 162 patients from the Southeast Swedish Health Care region included in the Swedish Rectal Cancer Trial between 1987-1990. New sections from the paraffin blocks of the preoperative biopsies and the surgical specimens were examined for apoptosis using the terminal deoxynucleotidyl transferase mediated digoxigenin nick end labeling (TUNEL) method.

RESULTS

The mean percentage of apoptotic cells was 0.3% (0-4%) and 1.1% (0-14.5%) for the preoperative biopsy and the surgical specimen, respectively. The authors analyzed the surgical specimens from nonirradiated patients and divided them into three groups by apoptotic index (AI) as follows: 0%, 0-1%, and > 1%. A high AI was associated with a decreased local recurrence rate compared with an intermediate or a low AI (P = 0.024). There was no significant relation between AI and survival. There was a significant reduction in the local recurrence rate for irradiated patients compared with the nonirradiated in the low (P = 0.015) and intermediate (P = 0.038) AI groups. In the high AI group, there were few recurrences and no significant difference was observed between irradiated and nonirradiated patients. The relative risk of death from rectal carcinoma in Dukes A-C patients was not significantly decreased by radiotherapy, but, in the intermediate AI group, there was a trend (P = 0.08) in favor of the irradiated patients.

CONCLUSION

A high AI in rectal carcinoma indicated a decreased local recurrence rate.

Cranial irradiation and central hypothyroidism

Cranial irradiation causes thyrotropin (TSH)-releasing hormone (TRH) secretory abnormalities. TRH deficiency leads to abnormal glycosylation of TSH alpha and beta subunits and loss of the normal circadian pattern of TSH secretion (low in the afternoon, a surge in the evening, higher at night). This disruption results in either mixed hypothyroidism (raised TSH with abnormal secretory kinetics) or central hypothyroidism (abnormal secretory kinetics without raised TSH). Although primary hypothyroidism is more common in the general population and cancer survivors, the cumulative incidence of central and mixed hypothyroidism is high during the ten years after cranial irradiation. Monitoring for decline in free thyroxine (FT(4)) and rise in serum TSH, and early recognition using TSH surge and TRH tests, are clinically valuable. Early thyroid hormone replacement therapy to achieve serum FT(4) in the upper half of the normal range is crucial for maintaining optimal health and growth in cancer survivors.

Ceramide-induced apoptosis of human thyroid cancer cells resistant to apoptosis by irradiation

Ionizing radiation (IR) induces apoptosis through, in part, cell membrane breakdown signals. Ceramide and diacylglycerol (DAG) are released after IR exposure, which act as second messengers to induce proapoptotic and antiapoptotic signals, respectively. We have previously shown, however, that thyroid cells are relatively resistant to IR-induced apoptosis. To investigate the mechanism of thyroid cell resistance to IR-related apoptosis, we determined the effects of ceramide and its release following exposure of human thyroid cancer cell lines to IR. Exogenous C2-ceramide (10-100 microM) activated the apoptosis process in all cell lines used. Exogenous C2-ceramide also activated a stress kinase, c-Jun N-terminal kinase UNK). The apoptotic action of ceramide was attenuated by serum or simultaneous activation of protein kinases C and A by phorbol esters and forskolin. Furthermore, 2-5 Gy IR had a differential effect on ceramide and DAG release in human thyroid cells; a weak and transient release of ceramide but a strong and sustained release of DAG. Our results indicated that the radioresistance properties of thyroid cancer cells probably reflect the dominance of anti-apoptotic signals, evoked by growth factor(s) and DAG, which override the apoptotic effect of ceramide released by human thyroid cells on exposure to IR, in spite of activation of proapoptotic pathway downstream of ceramide.

Oocyte apoptosis: like sand through an hourglass

Although the study of germ cell death is arguably still in its infancy as a field, several recent breakthroughs have provided the fodder for a story, replete with episodes of apparent mass cellular suicide if not murder, that will undoubtedly serve as a research base for many laboratories over the next several years. Death is known to strike the male and female germlines with roughly equal intensity, but the innate feature of male germ cells being self-renewing while those of the female are not places the death of oocytes in a completely different light. Indeed, the functional life span of the female gonads is defined in most species, including humans, by the size and rate of depletion of the precious endowment of oocytes enclosed within follicles in the ovaries at birth. This continuous loss of oocytes throughout life, referred to by many as the female biological clock, appears to be driven by a genetic program of cell death that is composed of players and pathways conserved from worms to humans. It is on this genetic pathway, and the role of its constituent molecules in regulating female germ cell fate, that this review will focus. Emphasis will be placed on those studies using genetic-null or transgenic models to explore the functional requirement of proteins, such as Bcl-2 family members, Apaf-1, and caspases in vertebrates to CED-9, CED-4, and CED-3 in Caenorhabditis elegans, in oocyte survival and death. Furthermore, hypotheses regarding the potential impact of translating what is now known of the oocyte death pathway into new approaches for the clinical diagnosis and management of female infertility and the menopause will be offered as a means to stimulate further research in this new and exciting field.

Molecular mechanisms of ionizing radiation-induced apoptosis

Ionizing radiation activates not only signalling pathways in the nucleus as a result of DNA damage, but also signalling pathways initiated at the level of the plasma membrane. Proteins involved in DNA damage recognition include poly(ADP ribose) polymerase (PARP), DNA-dependent protein kinase, p53 and ataxia- telangiectasia mutated (ATM). Many of these proteins are inactivated by caspases during the execution phase of apoptosis. Signalling pathways outside the nucleus involve tyrosine kinases such as stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK), protein kinase C, ceramide and reactive oxygen species. Recent evidence shows that tumour cells resistant to ionizing radiation-induced apoptosis have defective ceramide signalling. How these signalling pathways converge to activate the caspases is presently unknown, although in some cell types a role for calpain has been suggested.

Towards prediction and modulation of treatment response

The purpose of this paper is to evaluate new predictive assays and their potential to modulate treatment response. Their impact is presented in the context of three EORTC clinical trials in head and neck, lung and breast cancer, showing an improvement in survival by accelerated fractionation, concomitant use of cisplatin and radiotherapy and adjuvant hormonal treatment, respectively. Assays have been developed to predict the response to treatment by measuring tumor characteristics, such as the growth potential by the labeling index after i.v. injection of IdUrd, the extent of radiation-induced stable and unstable chromosome aberrations and the induction of apoptosis. These assays could guide us in the adaptation of the individual radiation doses and fractionation schedules. The measurement of the effect of cisplatin on DNA has become feasible with the development of antibodies against DNA adducts. In a recently completed phase II dose escalation trial with concomitant radiotherapy and daily cisplatin in lung cancer, we found that patients with high DNA adduct levels measured in the buccal mucosa, had a much better survival rate than patients with a low or undetectable amount of cisplatin DNA adducts. A better understanding of the signal transduction pathways involved in radiation-induced apoptosis may help to design studies aimed at modulating the apoptotic response. We and others have recently shown that alkylphospholipids, which inhibit mitogenic signaling, induce apoptosis in a variety of tumor cell lines. In combination with ionizing radiation, these compounds cause an enhancement of apoptotic cell kill. This type of signaling-based intervention study may form the basis for new therapeutic strategies. Pretreatment levels of apoptosis may be helpful in predicting treatment outcome, although the data so far show inconsistent results. The importance of evaluating other tumor-biological parameters, including cell kinetics should be stressed. Based on assays predicting reliably the response to hormonal therapy, a more appropriate choice can be made for therapeutic intervention with hormonal therapy and for selecting the appropriate adjuvant therapy in breast cancer patients. The development of a functional estrogen receptor assay (ER-FASAY), based on a yeast growth-assay, provides a way of estimating abnormal function of the receptor in tumors with a positive estrogen receptor score as measured by a classical immuno-histochemistry assay. This yeast assay can also detect different DNA mutations of the estrogen receptor existing in an individual tumor specimen.