Intron disruption of the annexin IV gene reveals novel transcripts

A Temporal Comparative RNA Transcriptome Profile of the Annexin Gene Family in the Salivary versus Lacrimal Glands of the Sjögren's Syndrome-Susceptible C57BL/6.NOD-Aec1Aec2 Mouse

A generally accepted hypothesis for the initial activation of an immune or autoimmune response argues that alarmins are released from injured, dying and/or activated immune cells, and these products complex with receptors that activate signal transduction pathways and recruit immune cells to the site of injury where the recruited cells are stimulated to initiate immune and/or cellular repair responses. While there are multiple diverse families of alarmins such as interleukins (IL), heat-shock proteins (HSP), Toll-like receptors (TLR), plus individual molecular entities such as Galectin-3, Calreticulin, Thymosin, alpha-Defensin-1, RAGE, and Interferon-1, one phylogenetically conserved family are the Annexin proteins known to promote an extensive range of biomolecular and cellular products that can directly and indirectly regulate inflammation and immune activities. For the present report, we examined the temporal expression profiles of the 12 mammalian annexin genes (Anxa1-11 and Anxa13), applying our temporal genome-wide transcriptome analyses of ex vivo salivary and lacrimal glands from our C57BL/6.NOD-Aec1Aec2 mouse model of Sjögren's Syndrome (SS), a human autoimmune disease characterized primarily by severe dry mouth and dry eye symptoms. Results indicate that annexin genes Anax1-7 and -11 exhibited upregulated expressions and the initial timing for these upregulations occurred as early as 8 weeks of age and prior to any covert signs of a SS-like disease. While the profiles of the two glands were similar, they were not identical, suggesting the possibility that the SS-like disease may not be uniform in the two glands. Nevertheless, this early pre-clinical and concomitant upregulated expression of this specific set of alarmins within the immune-targeted organs represents a potential target for identifying the pre-clinical stage in human SS as well, a fact that would clearly impact future interventions and therapeutic strategies.

Comparative study between in vivo- and in vitro-derived extracts of cactus (Opuntis ficus-indica L. Mill) against prostate and mammary cancer cell lines

Opuntia ficus-indica L. Mill cladodes are considered to be a source of an abundance of bioactive compounds. To identify a natural product that can be used in the chemoprevention and treatment of cancer, this study was conducted to produce an anticancer agent extracted from in vitro-derived cladodes of prickly pear cactus. Toward this goal, assays of seed germination and micropropagation revealed that the highest seed germination rate was 66% and that the highest shoot number per explant was obtained with benzyl adenine (BA) (2 mg/l) and kinetin (Kin) (1 mg/l) within 2 months, at 22.6. In addition, the maximum length of shoots was obtained with BA (3 mg/l) and Kin (0.5 mg/l), at 7.44 cm. The in vitro-derived cladode extract showed higher total phenolic and kaempferol contents than the in vivo-derived cladode extract (total phenolics 156.5 mg/g and 86 mg/g DW; kaempferol 2.807 mg/g and 1.304 mg/g DW, respectively). These remarkable results reflected the anticancer activity on the viability and proliferation/migration of PC3 prostate and mammary Mcf7-7 cells. In terms of cytotoxicity, the IC50 values on PC3 and Mcf7 cells were 5775.7 and 6311.3 μg/ml, respectively, showing dose-dependent increases. Meanwhile, from in vivo analyses of the plants, the IC50 values were 5927.93 and 6825.6 μg/ml, respectively, again showing dose-dependent increases.

Annexin A4 Is Dispensable for Hair Cell Development and Function

Annexin A4 (ANXA4) is a Ca²⁺-dependent phospholipid-binding protein that is specifically expressed in the cochlear and vestibular hair cells, but its function in the hair cells remains unknown. In the present study, we show that besides localizing on the plasma membrane, ANXA4 immunoreactivity is also localized at the tips of stereocilia in the hair cells. In order to investigate the role of ANXA4 in the hair cells, we established Anxa4 knockout mice using CRISPR/Cas9 technique. Unexpectedly, the development of both cochlear and vestibular hair cells is normal in Anxa4 knockout mice. Moreover, stereocilia morphology of Anxa4 knockout mice is normal, so is the mechano-electrical transduction (MET) function. Consistently, the auditory and vestibular functions are normal in the knockout mice. In conclusion, we show here that ANXA4 is dispensable for the development and function of hair cells, which might result from functional redundancy between ANXA4 and other annexin(s) in the hair cells.

Annexin Animal Models-From Fundamental Principles to Translational Research

Routine manipulation of the mouse genome has become a landmark in biomedical research. Traits that are only associated with advanced developmental stages can now be investigated within a living organism, and the in vivo analysis of corresponding phenotypes and functions advances the translation into the clinical setting. The annexins, a family of closely related calcium (Ca²⁺)- and lipid-binding proteins, are found at various intra- and extracellular locations, and interact with a broad range of membrane lipids and proteins. Their impacts on cellular functions has been extensively assessed in vitro, yet annexin-deficient mouse models generally develop normally and do not display obvious phenotypes. Only in recent years, studies examining genetically modified annexin mouse models which were exposed to stress conditions mimicking human disease often revealed striking phenotypes. This review is the first comprehensive overview of annexin-related research using animal models and their exciting future use for relevant issues in biology and experimental medicine.

Annexin A4 N-terminal peptide inhibits adenylyl cyclase 5 and limits β-adrenoceptor-mediated prolongation of cardiac action potential

Adenylyl cyclases (AC) are essential for the normal and pathophysiological response of many cells. In cardiomyocytes, the predominant AC isoforms are AC5 and AC6. Specific AC5 inhibition was suggested as an option for the treatment of heart failure potentially advantageous over β-blockers. We previously reported an interaction between the calcium-binding protein annexin A4 (ANXA4) and AC5 in human embryonic kidney 293 (HEK293) cells and an inhibition of cyclic adenosine monophosphate (cAMP) production in cardiomyocytes. Here, we investigated whether ANXA4 is able to differentiate between AC5 and AC6. In transfected HEK293 cells, ANXA4 specifically co-immunoprecipitated with AC5 and not with AC6, via its N-terminal domain. Both ANXA4 and a peptide comprising the ANXA4 N-terminal sequence (A4N_1-22 ) decreased the cAMP production in AC5 and not in AC6 expressing cells. In line with ACs inhibition, in myocytes from ANXA4-deficient mice, β-adrenoceptor (βAR) stimulation led to a higher increase of the L-type calcium current (I_CaL ) and to an excessive action potential duration (APD) prolongation as compared to wild-type cardiomyocytes. This enhanced response was reversed in the presence of A4N_1-22 peptide likely via specific AC5 inhibition. We conclude that via the N-terminal domain ANXA4 inhibits AC5 not AC6, and that A4N_1-22 as a specific AC5 inhibitor could serve as a novel therapeutic tool for the treatment of AC5-linked diseases.

Annexins - insights from knockout mice

Annexins are a highly conserved protein family that bind to phospholipids in a calcium (Ca2+) - dependent manner. Studies with purified annexins, as well as overexpression and knockdown approaches identified multiple functions predominantly linked to their dynamic and reversible membrane binding behavior. However, most annexins are found at multiple locations and interact with numerous proteins. Furthermore, similar membrane binding characteristics, overlapping localizations and shared interaction partners have complicated identification of their precise functions. To gain insight into annexin function in vivo, mouse models deficient of annexin A1 (AnxA1), A2, A4, A5, A6 and A7 have been generated. Interestingly, with the exception of one study, all mice strains lacking one or even two annexins are viable and develop normally. This suggested redundancy within annexins, but examining these knockout (KO) strains under stress conditions revealed striking phenotypes, identifying underlying mechanisms specific for individual annexins, often supporting Ca2+ homeostasis and membrane transport as central for annexin biology. Conversely, mice lacking AnxA1 or A2 show extracellular functions relevant in health and disease that appear independent of membrane trafficking or Ca2+ signaling. This review will summarize the mechanistic insights gained from studies utilizing mouse models lacking members of the annexin family.

Annexin A4 is a novel direct regulator of adenylyl cyclase type 5

Annexin A4 (AnxA4), a Ca(2+)- and phospholipid-binding protein, is up-regulated in the human failing heart. In this study, we examined the impact of AnxA4 on β-adrenoceptor (β-AR)/cAMP-dependent signal transduction. Expression of murine AnxA4 in human embryonic kidney (HEK)293 cells dose-dependently inhibited cAMP levels after direct stimulation of adenylyl cyclases (ACs) with forskolin (FSK), as determined with an exchange protein activated by cAMP-Förster resonance energy transfer (EPAC-FRET) sensor and an ELISA (control vs. +AnxA4: 1956 ± 162 vs. 1304 ± 185 fmol/µg protein; n = 8). Disruption of the anxA4 gene led to a consistent increase in intracellular cAMP levels in isolated adult mouse cardiomyocytes, with heart-directed expression of the EPAC-FRET sensor, stimulated with FSK, and as determined by ELISA, also in mouse cardiomyocytes stimulated with the β-AR agonist isoproterenol (ISO) (anxA4a(+/+) vs. anxA4a(-/-): 5.1 ± 0.3 vs. 6.7 ± 0.6 fmol/µg protein) or FSK (anxA4a(+/+) vs. anxA4a(-/-): 1891 ± 238 vs. 2796 ± 343 fmol/µg protein; n = 9-10). Coimmunoprecipitation experiments in HEK293 cells revealed a direct interaction of murine AnxA4 with human membrane-bound AC type 5 (AC5). As a functional consequence of AnxA4-mediated AC inhibition, AnxA4 inhibited the FSK-induced transcriptional activation mediated by the cAMP response element (CRE) in reporter gene studies (10-fold vs. control; n = 4 transfections) and reduced the FSK-induced phosphorylation of the CRE-binding protein (CREB) measured on Western blots (control vs. +AnxA4: 150 ± 17% vs. 105 ± 10%; n = 6) and by the use of the indicator of CREB activation caused by phosphorylation (ICAP)-FRET sensor, indicating CREB phosphorylation. Inactivation of AnxA4 in anxA4a(-/-) mice was associated with an increased cardiac response to β-AR stimulation. Together, these results suggest that AnxA4 is a novel direct negative regulator of AC5, adding a new facet to the functions of annexins.

Proteomic analysis of the sheep caruncular and intercaruncular endometrium reveals changes in functional proteins crucial for the establishment of pregnancy

The expression and regulation of endometrial proteins are crucial for conceptus implantation and development. However, little is known about site-specific proteome profiles of the mammalian endometrium during the peri-implantation period. We utilised a two-dimensional gel electrophoresis/mass spectrometry-based proteomics approach to compare and identify differentially expressed proteins in sheep endometrium. Caruncular and intercaruncular endometrium were collected on days 12 (C12) and 16 (C16) of the oestrous cycle and at three stages of pregnancy corresponding to conceptus pre-attachment (P12), implantation (P16) and post-implantation (P20). Abundance and localisation changes in differentially expressed proteins were determined by western blot and immunohistochemistry. In caruncular endometrium, 45 protein spots (5% of total spots) altered between day 12 of pregnancy (P12) and P16 while 85 protein spots (10% of total spots) were differentially expressed between P16 and C16. In intercaruncular endometrium, 31 protein spots (2% of total spots) were different between P12 and P16 while 44 protein spots (4% of total spots) showed differential expression between C12 and C16. The pattern of protein changes between caruncle and intercaruncle sites was markedly different. Among the protein spots with implantation-related changes in volume, 11 proteins in the caruncular endometrium and six proteins in the intercaruncular endometrium, with different functions such as protein synthesis and degradation, antioxidant defence, cell structural integrity, adhesion and signal transduction, were identified. Our findings highlight the different but important roles of the caruncular and intercaruncular proteins during early pregnancy.

Anxa4 Genes are Expressed in Distinct Organ Systems in Xenopus laevis and tropicalis But are Functionally Conserved

Anxa4 belongs to the multigenic annexin family of proteins which are characterized by their ability to interact with membranes in a calcium-dependent manner. Defined as a marker for polarized epithelial cells, Anxa4 is believed to be involved in many cellular processes but its functions in vivo are still poorly understood. Previously, we cloned Xanx4 in Xenopus laevis (now referred to as anxa4a) and demonstrated its role during organogenesis of the pronephros, providing the first evidence of a specific function for this protein during the development of a vertebrate. Here, we describe the strict conservation of protein sequence and functional domains of anxa4 during vertebrate evolution. We also identify the paralog of anxa4a, anxa4b and show its specific temporal and spatial expression pattern is different from anxa4a. We show that anxa4 orthologs in X. laevis and tropicalis display expression domains in different organ systems. Whilst the anxa4a gene is mainly expressed in the kidney, Xt anxa4 is expressed in the liver. Finally, we demonstrate Xt anxa4 and anxa4a can display conserved function during kidney organogenesis, despite the fact that Xt anxa4 transcripts are not expressed in this domain. This study highlights the divergence of expression of homologous genes during Xenopus evolution and raises the potential problems of using X. tropicalis promoters in X. laevis.

T-2 toxin induced Salmonella Typhimurium intoxication results in decreased Salmonella numbers in the cecum contents of pigs, despite marked effects on Salmonella-host cell interactions

The mycotoxin T-2 toxin and Salmonella Typhimurium infections pose a significant threat to human and animal health. Interactions between both agents may result in a different outcome of the infection. Therefore, the aim of the presented study was to investigate the effects of low and relevant concentrations of T-2 toxin on the course of a Salmonella Typhimurium infection in pigs. We showed that the presence of 15 and 83 μg T-2 toxin per kg feed significantly decreased the amount of Salmonella Typhimurium bacteria present in the cecum contents, and a tendency to a reduced colonization of the jejunum, ileum, cecum, colon and colon contents was noticed. In vitro, proteomic analysis of porcine enterocytes revealed that a very low concentration of T-2 toxin (5 ng/mL) affects the protein expression of mitochondrial, endoplasmatic reticulum and cytoskeleton associated proteins, proteins involved in protein synthesis and folding, RNA synthesis, mitogen-activated protein kinase signaling and regulatory processes. Similarly low concentrations (1-100 ng/mL) promoted the susceptibility of porcine macrophages and intestinal epithelial cells to Salmonella Typhimurium invasion, in a SPI-1 independent manner. Furthermore, T-2 toxin (1-5 ng/mL) promoted the translocation of Salmonella Typhimurium over an intestinal porcine epithelial cell monolayer. Although these findings may seem in favour of Salmonella Typhimurium, microarray analysis showed that T-2 toxin (5 ng/mL) causes an intoxication of Salmonella Typhimurium, represented by a reduced motility and a downregulation of metabolic and Salmonella Pathogenicity Island 1 genes. This study demonstrates marked interactions of T-2 toxin with Salmonella Typhimurium pathogenesis, resulting in bacterial intoxication.

Early osteogenic differential protein profile detected by proteomic analysis in human periodontal ligament cells

BACKGROUND AND OBJECTIVE

Human periodontal ligament cells play a pivotal role in maintaining periodontal ligament space, contain progenitors that are able to differentiate into cementoblasts/osteoblasts and have a tremendous potential to regenerate periodontal tissue. However, the exact molecular mechanisms governing the differentiation mechanisms of progenitors in periodontal ligament cells remain largely unknown. This study was carried out to investigate the differentially expressed proteins involved in the osteogenic differentiation of progenitors presented in periodontal ligament cells.

MATERIAL AND METHODS

Using two-dimensional gel electrophoresis, mass spectrometry and peptide mass fingerprinting, we analyzed the differential protein profiles of periodontal ligament cells undergoing mineralization.

RESULTS

Compared with undifferentiated periodontal ligament cells, 61 proteins in periodontal ligament cells undergoing differentiation showed at least a 1.5-fold change in intensity, of which 29 differentially expressed proteins were successfully identified by matrix-assisted laser-desorption ionization time-of-flight mass spectrometry. The expression of some of the identified proteins was further confirmed by western blotting and reverse transcription-polymerase chain reaction analysis. The identified proteins were cytoskeleton proteins and cytoskeleton-associated proteins, nuclear proteins and cell membrane-bound molecules.

CONCLUSION

Our results suggest that the proteins identified in this study may be associated with the unique function of periodontal ligament cells in maintaining periodontal tissue homeostasis, thus providing a comprehensive reference for understanding and investigating in greater detail the molecular mechanisms of periodontal ligament cells involved in periodontal regeneration.

Studies on localization and function of annexin A4a within urinary bladder epithelium using a mouse knockout model

Annexin A4 (anxA4) is a member of the Ca(2+)-dependent membrane-binding family of proteins implicated in the regulation of ion conductances, Ca(2+) homeostasis, and membrane trafficking. We demonstrate, in mice, that annexins 1-6 are present in whole bladder and exhibit differential expression in the urothelium. An anxA4a-knockout (anxA4a(-/-)) mouse model shows no protein in the urothelium by immunofluorescence and immunoblotting. In wild-type bladders, anxA4a in umbrella cells showed uniform cytoplasmic staining and some association with the nuclear membrane. Application of a hydrostatic pressure to bladders mounted in Ussing chambers resulted in redistribution of anxA4a from cytoplasm to cellular boundaries in the basal and intermediate cells but not in superficial umbrella cells. We hypothesized that anxA4a might be important for barrier function or for stretch-activated membrane trafficking. To test these hypotheses, we conducted a series of functional and morphological analyses on bladders from control and anxA4a(-/-) animals. The transepithelial resistances, water permeabilities, and urea permeabilities of anxA4a(-/-) bladders were not different from controls, indicating that barrier function was intact. Membrane trafficking in response to hydrostatic pressure as measured by capacitance increases was also normal for anxA4a(-/-) bladders. Cystometrograms performed on live animals showed that voiding frequency and intrabladder pressures were also not different. There were no differences in bladder surface morphology or cellular architecture examined by scanning and transmission electron microscopy, respectively. We conclude that loss of anxA4 from the urothelium does not affect barrier function, membrane trafficking, or normal bladder-voiding behavior.

Gene trap mutagenesis

Our ability to genetically manipulate the mouse has had a great impact on medical research over the last few decades. Mouse genetics has developed into a powerful tool for dissecting the genetic causes of human disease and identifying potential targets for pharmaceutical intervention. With the recent sequencing of the human and mouse genomes, a large number of novel genes have been identified whose function in normal and disease physiology remains largely unknown. Government-sponsored multinational efforts are underway to analyze the function of all mouse genes through mutagenesis and phenotyping, making the mouse the interpreter of the human genome. A number of technologies are available for the generation of mutant mice, including gene targeting, gene trapping and transposon, chemical or radiation-induced mutagenesis. In this chapter, we review the current status of gene trapping technology, including its applicability to conditional mutagenesis.

Paraoxonase-2 Deficiency Aggravates Atherosclerosis in Mice Despite Lower Apolipoprotein-B-containing Lipoproteins

Paraoxonases (PONs) are a family of proteins that may play a significant role in providing relief from both toxic environmental chemicals as well as physiological oxidative stress. Although the physiological roles of the PON family of proteins, PON1, PON2, and PON3, remain unknown, epidemiological, biochemical, and mouse genetic studies of PON1 suggest an anti-atherogenic function for paraoxonases. To determine whether PON2 plays a role in the development of atherosclerosis in vivo, we generated PON2-deficient mice. When challenged with a high fat, high cholesterol diet for 15 weeks, serum levels of high density lipoprotein cholesterol, triglycerides, and glucose were not significantly different between wild-type and PON2-deficient mice. In contrast, serum levels of very low density lipoprotein (VLDL)/low density lipoprotein (LDL) cholesterol were significantly lower (-32%) in PON2-deficient mice compared with wild-type mice. However, despite lower levels of VLDL/LDL cholesterol, mice deficient in PON2 developed significantly larger (2.7-fold) atherosclerotic lesions compared with their wild-type counterparts. Enhanced inflammatory properties of LDL, attenuated anti-atherogenic capacity of high density lipoprotein, and a heightened state of oxidative stress coupled with an exacerbated inflammatory response from PON2-deficient macrophages appear to be the main mechanisms behind the larger atherosclerotic lesions in PON2-deficient mice. These results demonstrate that PON2 plays a protective role in atherosclerosis.

Cyclic changes and hormonal regulation of annexin IV mRNA and protein in human endometrium

Annexin IV (ANXA4) belongs to a ubiquitous family of Ca(2+)-dependent phospholipid-binding proteins. ANXA4 has been shown to be involved in a range of physiological functions including ion channel regulation, exocytosis and Ca(2+)-dependent signal transduction. The aims of this study were to fully characterize ANXA4 mRNA and protein in human endometrium during the menstrual cycle and to investigate the hormonal regulation of ANXA4. ANXA4 mRNA expression was quantified by real-time PCR in fresh endometrial tissue from cycling women, and protein expression was analysed by immunohistochemistry and western blotting. Hormonal regulation of ANXA4 transcription and translation was investigated using an endometrial explant system. ANXA4 mRNA was significantly up-regulated during mid-secretory (MS) and late-secretory (LS) phases compared with proliferative phases during the menstrual cycle. ANXA4 protein was localized to glandular and luminal epithelium and was present in high levels throughout the menstrual cycle except during early-secretory (ES) phase, when it was significantly reduced. Our data also show that, in proliferative explants, progesterone significantly increased the ANXA4 mRNA and protein after 48h in culture. Estrogen did not have any significant effects. This is the first study to show that ANXA4 transcription and translation are regulated by progesterone and suggests that ANXA4 may be important in regulating ion and water transport across the endometrial epithelium.

Expression and functions of annexins in the kidney

This review article summarizes current knowledge about the locations and possible functions of annexin family members in the kidney. Beginning with an introduction on common structural and biochemical features as well as general functional characteristics of annexins, the paper focuses on individual members with documented and/or proposed physiological relevance for renal development, structure, and functions. Three main aspects of annexin function in kidney epithelia emerge from the available experimental data. First, annexins are required for membrane organization and membrane transport events required for the establishment/maintenance of epithelial polarity. Second, there is accumulating evidence of an association of annexins with ion channels, as membrane-guiding auxiliary proteins or modulators of channel activity. Last but not least, some annexins seem to work as extracellular autocrine modulators of receptor function under different physiological conditions.

The gene trap resource: a treasure trove for hemopoiesis research

The laboratory mouse is an invaluable tool for functional gene discovery because of its genetic malleability and a biological similarity to human systems that facilitates identification of human models of disease. A number of mutagenic technologies are being used to elucidate gene function in the mouse. Gene trapping is an insertional mutagenesis strategy that is being undertaken by multiple research groups, both academic and private, in an effort to introduce mutations across the mouse genome. Large-scale, publicly funded gene trap programs have been initiated in several countries with the International Gene Trap Consortium coordinating certain efforts and resources. We outline the methodology of mammalian gene trapping and how it can be used to identify genes expressed in both primitive and definitive blood cells and to discover hemopoietic regulator genes. Mouse mutants with hematopoietic phenotypes derived using gene trapping are described. The efforts of the large-scale gene trapping consortia have now led to the availability of libraries of mutagenized ES cell clones. The identity of the trapped locus in each of these clones can be identified by sequence-based searching via the world wide web. This resource provides an extraordinary tool for all researchers wishing to use mouse genetics to understand gene function.

Cactus pear: a natural product in cancer chemoprevention

BACKGROUND

Cancer chemoprevention is a new approach in cancer prevention, in which chemical agents are used to prevent cancer in normal and/or high-risk populations. Although chemoprevention has shown promise in some epithelial cancers, currently available preventive agents are limited and the agents are costly, generally with side effects. Natural products, such as grape seed, green tea, and certain herbs have demonstrated anti-cancer effects. To find a natural product that can be used in chemoprevention of cancer, we tested Arizona cactus fruit solution, the aqueous extracts of cactus pear, for its anti-cancer effects in cultured cells and in an animal model.

METHOD

Aqueous extracts of cactus pear were used to treat immortalized ovarian and cervical epithelial cells, as well as ovarian, cervical, and bladder cancer cells. Aqueous extracts of cactus pear were used at six concentrations (0, 0.5, 1, 5, 10 or 25%) to treat cells for 1, 3, or 5 days. Growth inhibition, apoptosis induction, and cell cycle changes were analyzed in the cultured cells; the suppression of tumor growth in nude mice was evaluated and compared with the effect of a synthetic retinoid N-(4-hydroxyphernyl) retinamide (4-HPR), which is currently used as a chemoprevention agent. Immunohistochemistry staining of tissue samples from animal tumors was performed to examine the gene expression.

RESULTS

Cells exposed to cactus pear extracts had a significant increase in apoptosis and growth inhibition in both immortalized epithelial cells and cancer cells in a dose- and time-dependent manner. It also affected cell cycle of cancer cells by increasing G1 and decreasing G2 and S phases. Both 4-HPR and cactus pear extracts significantly suppressed tumor growth in nude mice, increased annexin IV expression, and decreased VEGF expression.

CONCLUSION

Arizona cactus pear extracts effectively inhibited cell growth in several different immortalized and cancer cell cultures, suppressed tumor growth in nude mice, and modulated expression of tumor-related genes. These effects were comparable with those caused by a synthetic retinoid currently used in chemoprevention trials. The mechanism of the anti-cancer effects of cactus pear extracts needs to be further studied.