Vascular smooth muscle cell apoptosis promotes transplant arteriosclerosis through inducing the production of SDF-1α

Transplant arteriosclerosis is a leading cause of late allograft loss. Medial smooth muscle cell (SMC) apoptosis is considered to be an important event in transplant arteriosclerosis. However, the precise contribution of medial SMC apoptosis to transplant arteriosclerosis and the underlying mechanisms remain unclear. We transferred wild-type p53 to induce apoptosis of cultured SMCs. We found that apoptosis induces the production of SDF-1α from apoptotic and neighboring viable cells, resulting in increased SDF-1α in the culture media. Conditioned media from Ltv-p53-transferred SMCs activated PI3K/Akt/mTOR and MAPK/Erk signaling in a SDF-1α-dependent manner and thereby promoted mesenchymal stem cell (MSC) migration and proliferation. In a rat aorta transplantation model, lentivirus-mediated BclxL transfer selectively inhibits medial SMC apoptosis in aortic allografts, resulting in a remarkable decrease of SDF-1α both in allograft media and in blood plasma, associated with diminished recruitment of CD90(+)CD105(+) double-positive cells and impaired neointimal formation. Systemic administration of rapamycin or PD98059 also attenuated MSC recruitment and neointimal formation in the aortic allografts. These results suggest that medial SMC apoptosis is critical for the development of transplant arteriosclerosis through inducing SDF-1α production and that MSC recruitment represents a major component of vascular remodeling, constituting a relevant target and mechanism for therapeutic interventions.

Will posttranslational modifications of brain proteins provide novel serological markers for dementias?

Drug development for dementias is significantly hampered by the lack of easily accessible biomarkers. Fluid biomarkers of dementias provide indications of disease stage, but have little prognostic value, cannot detect early pathological changes, and can only be measured in CSF (cerebrospinal fluid) which significantly limits their applicability. In contrast, imaging based biomarkers can provide indications of probability of disease progression, yet are limited in applicability due to cost, radiation and radio-tracers. These aspects highlight the need for other approaches to the development of biomarkers of dementia, which should focus on not only providing information about pathological changes, but also on being measured easily and reproducibly. For other diseases, focus on development of assays monitoring highly specific protease-generated cleavage fragments of proteins has provided assays, which in serum or plasma have the ability to predict early pathological changes. Proteolytic processing of brain proteins, such as tau, APP, and α-synuclein, is a key pathological event in dementias. Here, we speculate that aiming biomarker development for dementias at detecting small brain protein degradation fragments of generated by brain-derived proteases specifically in blood samples could lead to the development of novel markers of disease progression, stage and importantly of treatment efficacy.

Vitreous surgery for macular hole-related retinal detachment after phacoemulsification cataract extraction: 10-year retrospective review

PURPOSE

To evaluate the visual and anatomical results of surgery for macular hole-related retinal detachment (MHRD) after phacoemulsification cataract extraction.

METHODS

Data for all patients who underwent surgery for MHRD after phacoemulsification cataract extraction from 1 December 1998 to 30 September 2008 in one hospital were evaluated. Patient characteristics, best-corrected visual acuity (VA) preoperatively and at last examination, surgical technique, anatomical success, and follow-up period were extracted and analysed statistically.

RESULTS

A total of 13 625 eyes of 10 076 patients who had phacoemulsification cataract surgery were included. In the follow-up period, 10 cases of MHRD in nine patients were observed, of which seven eyes had high myopia. The mean axial length was 30.97 ± 1.36 mm (29.19, 32.97) and mean myopia was-19.35 ± 1.93 (-7.5,-3.5) dioptres. Overall anatomical success was achieved in 90% (9 out of 10 eyes). There was no statistically significant difference (P=0.240) between the logarithm of the MAR VA before the phacoemulsification cataract extraction and after MHRD surgical repair. VA increased in three eyes but decreased in the other seven after MHRD surgery.

CONCLUSIONS

As a primary procedure, vitreous surgery combined with other necessary adjunct procedures such as membrane peeling and retinal tamponade seems to be successful in achieving anatomical success. However, VA improvement is dependent on the type of macular lesion and not the surgical procedure.

Investigation of two novel biochemical markers of inflammation, matrix metalloproteinase and cathepsin generated fragments of C-reactive protein, in patients with ankylosing spondylitis

OBJECTIVES

Ankylosing spondylitis (AS) is a chronic inflammation of the spine and the sacroiliac joints. Current markers of inflammation, such as C-reactive protein (CRP), are reflecting the production of an acute phase reactant rather than tissue specific inflammation, but the use of CRP as a diagnostic and prognostic marker for AS has not provided the sought accuracy and specificity. We hypothesized that local enzymatic activity in the disease-affected tissue, which is associated with extensive tissue turnover may, by cleavage, modify the CRP produced in the liver. These cleavage products may provide additional information on systemic inflammation as compared to that of full-length CRP. We investigated whether these CRP degradation products would provide additional diagnostic value in AS patients compared to full-length CRP.

METHODS

CRP fragments were identified by mass-spectrometry. Two fragments were selected for ELISA development. One assay exclusively identified a matrix metalloproteinase (MMP) generated fragment, CRP-MMP, whereas the other assay identified a cathepsin generated fragment, CRP-CAT. Full-length CRP, CRP-MMP and CRP-CAT were measured in serum samples from 40 AS patients and 40 sex- and age-matched controls.

RESULTS

Full-length CRP was not elevated in AS patients compared to controls, whereas CRP-MMP was elevated by 25% (p<0.001) and CRP-CAT by 50% (p<0.0001). The Area Under Curve of the Receiver-Operator Characteristic curve of CRP-CAT was the highest with 77%.

CONCLUSIONS

MMP and cathepsin degraded CRP provided more discriminative diagnostic potential compared to that of full-length CRP in this current study. These data suggest that different pools of CRP may provide insight into the inflammation processes in AS.

Putative function of TAP63α during endochondral bone formation

P63, a member of the P53 tumor suppressor family, is known to play important functions in cancer and development. Interestingly, previous studies have shown that p63 null mice are absent or have truncated limbs, while mutations in human P63 cause several skeletal syndromes that also show limb and digit abnormalities, suggesting its essential role in long bone development. Indeed, we detected increased level of p63 transcript in hypertrophic MCT cells (an established cell model of chondrocyte maturation) than in proliferative MCT cells. To investigate the in vivo role of P63 upon endochondral bone formation, we have established transgenic mouse lines in which HA- and Flag-tagged TAP63α (the longest P63 isoform) is driven by the hypertrophic chondrocyte-specific Col10a1 regulatory elements. Skeletal staining of Col10a1-TAP63α transgenic mice at either embryonic day 17.5 (E17.5) or postnatal day 1 (P1) observed accelerated ossification in long bone, digit and tail bones compared to their wild-type littermates, suggesting a putative function of P63 during skeletal development. We also detected decreased level of Sox9 and Bcl-2 transcripts, while Alp and Ank are slightly upregulated in Col10a1-TAP63α transgenic mouse limbs. Further immunohistochemical analysis confirmed the decreased Sox9 expression in the proliferative and hypertrophic zone of these mice. Von Kossa staining suggests increased mineralization in hypertrophic zone of transgenic mice compared to littermate controls. Together, our results suggest a role of TAP63α upon skeletal development. TAP63a may promote endochondral ossification through interaction with genes relevant to matrix mineralization and chondrocyte maturation or apoptosis.

Overexpression of ribosomal RNA in prostate cancer is common but not linked to rDNA promoter hypomethylation

Alterations in nucleoli, including increased numbers, increased size, altered architecture and increased function are hallmarks of prostate cancer cells. The mechanisms that result in increased nucleolar size, number and function in prostate cancer have not been fully elucidated. The nucleolus is formed around repeats of a transcriptional unit encoding a 45S ribosomal RNA (rRNA) precursor that is then processed to yield the mature 18S, 5.8S and 28S RNA species. Although it has been generally accepted that tumor cells overexpress rRNA species, this has not been examined in clinical prostate cancer. We find that indeed levels of the 45S rRNA, 28S, 18S and 5.8S are overexpressed in the majority of human primary prostate cancer specimens as compared with matched benign tissues. One mechanism that can alter nucleolar function and structure in cancer cells is hypomethylation of CpG dinucleotides of the upstream rDNA promoter region. However, this mechanism has not been examined in prostate cancer. To determine whether rRNA overexpression could be explained by hypomethylation of these CpG sites, we also evaluated the DNA methylation status of the rDNA promoter in prostate cancer cell lines and the clinical specimens. Bisulfite sequencing of genomic DNA revealed two roughly equal populations of loci in cell lines consisting of those that contained densely methylated deoxycytidine residues within CpGs and those that were largely unmethylated. All clinical specimens also contained two populations with no marked changes in methylation of this region in cancer as compared with normal. We recently reported that MYC can regulate rRNA levels in human prostate cancer; here we show that MYC mRNA levels are correlated with 45S, 18S and 5.8S rRNA levels. Further, as a surrogate for nucleolar size and number, we examined the expression of fibrillarin, which did not correlate with rRNA levels. We conclude that rRNA levels are increased in human prostate cancer, but that hypomethylation of the rDNA promoter does not explain this increase, nor does hypomethylation explain alterations in nucleolar number and structure in prostate cancer cells. Rather, rRNA levels and nucleolar size and number relate more closely to MYC overexpression.

MMP mediated type V collagen degradation (C5M) is elevated in ankylosing spondylitis

OBJECTIVES

Type V collagen has been demonstrated to control fibril formation. The aim of this study was to develop an ELISA capable of detecting a fragment of type V collagen generated by MMP-2/9 and to evaluate the assay as biomarker for ankylosing spondylitis (AS).

DESIGN AND METHODS

A fragment unique to type V collagen and generated by both MMP-2/9 cleaved at the amino acid position 1317 (C5M) was selected for ELISA development. 40 AS patients and 40 age-matched controls were evaluated.

RESULTS

An ELISA detecting C5M with inter- and intra-assay variations of 9.1% and 4.4% was developed. C5M levels were significantly higher in AS patients compared to controls, 229% (p<0.0001). The diagnostic AUC was 83%.

CONCLUSIONS

This ELISA is the first for detecting type V collagen degradation. AS patients had highly elevated levels of MMP mediated type V collagen degradation. The prognostic and diagnostic values need to be further investigated in additional clinical settings.

Runx2 contributes to murine Col10a1 gene regulation through direct interaction with its cis-enhancer

We have recently shown that a 150-bp Col10a1 distal promoter (-4296 to -4147 bp) is sufficient to direct hypertrophic chondrocyte-specific reporter (LacZ) expression in vivo. More recently, through detailed sequence analysis we identified two putative tandem-repeat Runx2 binding sites within the 3'-end of this 150-bp region (TGTGGG-TGTGGC, -4187 to -4176 bp). Candidate electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation, and transfection studies demonstrate that these putative Runx2 sites bind Runx2 and mediate upregulated Col10a1/reporter activity in vitro. Transgenic studies using the 5'-sequence without Runx2 sites were not able to drive the cell-specific LacZ reporter activity, suggesting the in vivo requirement of the Runx2 sites located in the 3'-end in mediating Col10a1/reporter expression. Indeed, mutating the Runx2 sites in the context of the 150-bp promoter abolishes its capacity to drive hypertrophic chondrocyte-specific reporter expression in transgenic mice. We have also generated multiple transgenic mouse lines using only the 3'-sequence containing the Runx2 sites to drive the LacZ gene. Interestingly, no hypertrophic chondrocyte-specific blue staining was observed in these transgenic mice. Together, our data support that Runx2 directly interacts with murine Col10a1 cis-enhancer. This interaction is required but not sufficient for cell-specific Col10a1 promoter activity in vivo. Additional cooperative/repressive elements within the 5'- or 3'-sequences of this 150-bp promoter are needed to work with Runx2 together to mediate cell-specific Col10a1 expression. Further delineation of these elements/factors has the potential to identify novel therapeutic targets for multiple skeletal disorders, including osteoarthritis, that show abnormal Col10a1 expression and altered chondrocyte maturation.

Levels of Circulating MMCN-151, a Degradation Product of Mimecan, Reflect Pathological Extracellular Matrix Remodeling in Apolipoprotein E Knockout Mice

AIM

Arterial extracellular matrix (ECM) remodeling by matrix metalloproteinases (MMPs) is one of the major hallmarks of atherosclerosis. Mimecan, also known as osteoglycin has been implicated in the integrity of the ECM. This study assessed the validity of an enzyme-linked immunosorbent assay (ELISA) developed to measure a specific MMP12-derived fragment of mimecan, MMCN-151, in apolipoprotein-E knockout (ApoE-KO) mice.

METHODS AND RESULTS

A mouse monoclonal antibody raised against MMCN-151 was used to develop a competitive ELISA. The assay was validated using samples from 20 ApoE-KO and 20 wild type [C57 BL/6] male mice fed a normal or high-fat diet (HFD) for up to 20 weeks. The technical reliability of the assay was established with intra-assay variability <2% and inter-assay variability <10%. The lowest limit of quantification of MMCN-151 was 0.5 ng/ml. ApoE-KO mice fed a HFD for 20 weeks had four-fold increased circulating levels of MMCN-151 compared to baseline, whereas MMCN-151 levels in control mice on HFD increased two-fold compared with baseline. After 10 weeks of a HFD, a significant difference in MMCN-151 levels was observed between ApoE-KO and control mice (P = 0.005) and became more significant at 20 weeks (P = 0.002).

CONCLUSIONS

The newly developed assay is a reliable detector of MMCN-151 levels which ultimately may be useful indicators of arterial remodeling in patients affected by atherosclerotic disease.

Serological survey of antibodies to influenza A viruses in a group of people without a history of influenza vaccination

A serological survey for antibodies to influenza viruses was performed in China on a group of people without a history of influenza vaccination. Using the haemagglutination inhibition (HI) assay, we found seropositivity rates for seasonal H3N2 to be significantly higher than those for seasonal H1N1. Samples positive for antibodies to the pandemic (H1N1) 2009 virus increased from 0.6% pre-outbreak to 4.5% (p <0.01) at 1 year post-outbreak. Interestingly, HI and neutralization tests showed that 1.4% of people in the group have antibodies recognizing H9N2 avian influenza viruses, suggesting that infection with this subtype may be more common than previously thought.

Rapid detection of Vibrio metschnikovii in aquatic products by real-time PCR

PCR and SYBR Green I real-time PCR techniques were applied to the rapid detection of Vibrio metschnikovii by designing primers based on infC (initiation factor 3) gene sequence. The specificity, sensitivity, and practical applications of the methods have been also analyzed. The methods showed high detecting specificity with no cross amplifications of other closely related and nonrelated species; they provide a simple and rapid tool for V. metschnikovii detection with high sensitivity and specificity.

RPB5-mediating protein is required for the proliferation of hepatocellular carcinoma cells

RPB5-mediating protein (RMP) is associated with the RNA polymerase II subunit RPB5. RMP functionally counteracts the transcriptional activation of hepatitis B virus X protein that has been shown to play a role in the development of hepatocellular carcinoma (HCC). However, the effect of RMP on the growth of HCC remains unclear. In this study, we characterized the potential role of RMP in the proliferation of human HCC cells using two cell lines, SMMC-7721 and HepG2. We found that RMP expression increased when HCC cells were treated with (60)Co γ-irradiation. Cell growth and colony formation assays suggest that RMP plays an antiapoptotic role in the proliferation and growth of HCC cells. We also show that RMP depletion induced the G(2) arrest of HCC cells characterized by the decreased expression of Cdk1 and Cyclin B. Tumor formation assays further confirmed the in vivo requirement of RMP during HCC growth. In conclusion, our results demonstrate that RMP is a radiation-sensitive factor, and it may play essential roles in HCC growth by affecting the proliferation and apoptosis of HCC cells.

Randomised clinical trial: the effects of perioperative probiotic treatment on barrier function and post-operative infectious complications in colorectal cancer surgery - a double-blind study

BACKGROUND

Infection following abdominal operation remains a major factor affecting the morbidity of patients after surgery.

AIM

To determine the effects of perioperative administration of probiotics on the gut barrier function and the surgical outcome in patients undergoing elective colorectal surgery.

METHODS

One hundred patients with colorectal carcinoma were randomly divided into the control group (n = 50) and the probiotics group (n = 50). The probiotics were given orally for 6 days preoperatively and 10 days post-operatively. Outcomes were measured by bacterial translocation, gut permeability, the effect on the faecal microbiota, and the clinical outcomes such as infectious-related complications and gut defecation function.

RESULTS

Compared with the control group, probiotics group had increased transepithelial resistance (P < 0.05), reduced transmucosal permeation of horseradish peroxidase and lactulose/mannitol ratio, reduced bacterial translocation (P < 0.05), decreased ileal-bile acid binding protein (P < 0.05) and positive rate of blood bacterial DNA (P < 0.05) and an enhanced mucosal tight junction protein expression. They had decreased blood enteropathogenic bacteria and increased faecal bacterial variety. The post-operative recovery of peristalsis, incidence of diarrhoea, and infectious-related complications were also improved.

CONCLUSION

Probiotics can improve the integrity of gut mucosal barrier by benefiting the faecal microbiota, and decreasing infectious complications in patients with colorectal cancer undergoing colorectomy.

TEC protein tyrosine kinase is involved in the Erk signaling pathway induced by HGF

BACKGROUND/AIMS

TEC, a member of the TEC family of non-receptor type protein tyrosine kinases, has recently been suggested to play a role in hepatocyte proliferation and liver regeneration. This study aims to investigate the putative mechanisms of TEC kinase regulation of hepatocyte differentiation, i.e. to explore which signaling pathway TEC is involved in, and how TEC is activated in hepatocyte after hepatectomy and hepatocyte growth factor (HGF) stimulation.

METHODS

We performed immunoprecipitation (IP) and immunoblotting (IB) to examine TEC tyrosine phosphorylation after partial hepatectomy in mice and HGF stimulation in WB F-344 hepatic cells. The TEC kinase activity was determined by in vitro kinase assay. Reporter gene assay, antisense oligonucleotide and TEC dominant negative mutant (TEC(KM)) were used to examine the possible signaling pathways in which TEC is involved. The cell proliferation rate was evaluated by (3)H-TdR incorporation.

RESULTS

TEC phosphorylation and kinase activity were increased in 1 h after hepatectomy or HGF treatment. TEC enhanced the activity of Elk and serum response element (SRE). Inhibition of MEK1 suppressed TEC phosphorylation. Blocking TEC activity dramatically decreased the activation of Erk. Reduced TEC kinase activity also suppressed the proliferation of WB F-344 cells. These results suggest TEC is involved in the Ras-MAPK pathway and acts between MEK1 and Erk.

CONCLUSIONS

TEC promotes hepatocyte proliferation and regeneration and is involved in HGF-induced Erk signaling pathway.

Association of single-nucleotide polymorphisms in HLA class II/III region with knee osteoarthritis

OBJECTIVE

A genome-wide association study and a replication using Japanese, Spanish and Greek Caucasian populations have recently indicated two single-nucleotide polymorphisms (SNPs) (rs7775228 and rs10947262) associated with knee Osteoarthritis (OA) susceptibility. We have further evaluated the association in knee OA subjects from Han Chinese and Australian Caucasian origin.

METHODS

Two independent case-control association studies were performed using Han Chinese and Australian Caucasian populations. The two SNPs were genotyped in patients who had primary symptomatic knee OA with radiographic confirmation and/or received total knee replacement surgery as well as in matched controls. They were subjected to statistic analyses.

RESULTS

A total of 991 OA patients and 1536 controls were genotyped. No significant difference was detected in genotype or allele frequencies of the two SNPs between knee OA and control groups in the two populations (all P>0.05). The association was also negative even after stratification by sex, body mass index (BMI) and Kellgren/Lawrence scores. The significant heterogeneity was detected between Chinese and Japanese (both P<0.05). In the Caucasian samples, no significant heterogeneity was detected (both P>0.05). The result of meta-analysis showed significant association between knee OA and rs10947262 in total subjects [summary OR=1.26, 95%confidence intervals (CI)=1.07-1.27, P=3 × 10(-8)] and in Caucasian samples (summary OR=1.28, 95%CI=1.04-1.57, P=0.02).

CONCLUSION

We demonstrated no association between the two SNPs in human leukocyte antigen (HLA) class II/III region and knee OA in Han Chinese population. A significant association was detected between SNP rs10947262 and knee OA in Caucasian subjects. Further replication studies are required to identify the impact of controversial association.

Enhanced anorexigenic signaling in lean obesity resistant syndecan-3 null mice

Obesity is associated with increased risk of diabetes, cardiovascular disease and several types of cancers. The hypothalamus is a region of the brain critical in the regulation of body weight. One of the critical and best studied hypothalamic circuits is comprised of the melanocortinergic orexigenic agouti-related protein (AgRP) and anorexigenic α-melanocyte stimulating hormone (α-MSH) neurons. These neurons project axons to the same hypothalamic target neurons and balance each other's activity leading to body weight regulation. We previously showed that the brain proteoglycan syndecan-3 regulates feeding behavior and body weight, and syndecan-3 null (SDC-3(-/-)) mice are lean and obesity resistant. Here we show that the melanocortin agonist Melanotan II (MTII) potently suppresses food intake and activates the hypothalamic paraventricular nuclei (PVN) in SDC-3(-/-) mice based on c-fos immunoreactivity. Interestingly, we determined that the AgRP neuropeptide is reduced in the PVN of SDC-3(-/-) mice compared to wild type mice. In contrast, neuropeptide Y, coexpressed in the AgRP neuron, is not differentially expressed nor is the counteracting neuropeptide α-MSH. These findings are unprecedented and indicate that AgRP protein localization can be selectively regulated within the hypothalamus resulting in altered neuropeptide response and tone.

Liquids at large negative pressures: water at the homogeneous nucleation limit

An isochoric cooling method for obtaining unprecedented tensions on liquids was used to determine the homogeneous nucleation limit for stretching of water at a variety of water densities. At densities in the range 0.55 to 0.68 gram per milliliter (g/ml), the data agree with the homogeneous nucleation temperatures measured by Skripov for superheated water at positive pressures. At densities between 0.68 and 0.93 g/ml, cavitation occurred only at negative pressures (that is, under tension). The cavitation tensions measured were in excellent agreement with those predicted by Fisher's 1948 vapor nucleation theory. A maximum tension of 140 megapascals (=1400 bars) was reached at 42 degrees C, which lies on an extrapolation of the line of isobaric density maxima. At higher densities, cavitation of droplets that survived heterogeneous nucleation failed to occur at all unless provoked, at much lower temperatures, by freezing. This observation confirms the existence of a density maximum at 42 degrees C and -140 megapascals and hence greatly strengthens the basis for Speedy's conjecture of a reentrant spinodal for water.

Abstract 3919: Potential roles of oncogenic ΔNP63α during bone and bone cancer formation

P63 belongs to the P53 tumor suppressor gene family. Due to its alternative promoter usage and splicing, p63 consists of two major subtypes (TAp63 and ΔNp63) and six different isoforms (TAp63α, β, or γ and ΔNp63α, β, or γ). These isoforms have been shown to play distinct biological functions in cancer and development. P63, especially the ΔNp63α variant, has been suggested to play an oncogenic role in cancer progression, including bone-related tumors such as giant cell tumor of bone and osteosarcoma. Interestingly, P63 has previously been shown to be an essential player for limb development. This raises the possibility that there might be a specific mechanism linking P63 regulation of bone and bone cancer formation.

The type X collagen gene (Col10a1) is a specific marker of hypertrophic chondrocytes during endochondral bone formation. As a matrix protein, type X collagen also functions as a regulatory molecule that affects chondrocyte mineralization, apoptosis, and angiogenesis. Therefore, transcriptional regulators critical for Col10a1 expression are also expected to affect the apoptotic pathway that occurs during bone cancer formation. By real-time RT-PCR and proteomic approaches using a MCT cell model, we demonstrate here that P63 contributes to regulation of Col10a1 expression in vitro. We also have data which supports that Runx2 regulates cell-specific Col10a1 expression via the Runx2 binding sites found within the Col10a1 cis-enhancer. This is intriguing since p63 was previously shown to interact with Runx2 by yeast two-hybrid approach. Moreover, we have generated a mouse model in which Runx2 was driven by the cell-specific Col10a1 control element. Our preliminary results showed that these Col10a1-Runx2 transgenic mice have enhanced Runx2 and Col10a1 expression, a longer hypertrophic zone, altered chondrocyte maturation, apoptosis, and disturbed ossification. These results suggest the decreased apoptotic activity mediated by Runx2, whereas elevated Runx2 expression has been associated with osteosarcoma development and chondrosarcoma progression. To address the potential in vivo relevance of P63 on bone and cancer formation, we have established Col10a1-ΔNp63α transgenic mouse lines using the same Col10a1 control element. Characterization of these transgenic mice will allow us to study if this oncogenic P63 isoform regulates Col10a1 expression in vivo and if this regulation is within the network regulating both bone and bone cancer formation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3919.

Abstract 4972: Putative mechanism of TAP63α regulation of chondrocyte maturation during long bone development

p63 is the mouse homologue of the well-known tumor suppressor P53. While it remains controversial as to whether P63 functions as a tumor suppressor gene or an oncogene, mouse genetic studies and mutation analysis of human SHFM syndrome (Split Hand/Foot Malformation) have clearly demonstrated that P63 plays an important role in skin and limb development. The truncated limbs observed in p63 null mice suggest that P63 may contribute to long bone development by playing a role during endochondral bone formation. However, how P63 regulates target gene expression and is linked to endochondral ossification remains largely unknown. Here we present some preliminary data suggesting that P63 may regulate type X collagen gene (Col10a1) expression, thereby impacting the process of chondrocyte maturation.

The type X collagen gene (Col10a1) is specifically expressed in hypertrophic chondrocytes, a critical cell stage linking both skeletal development and multiple skeletal diseases. We have previously shown that a 150-bp Col10a1 cis-enhancer is sufficient to mediate its cell-specific expression in vivo. Our further in vitro studies suggest that Runx2, a master transcription factor for osteoblast differentiation as well as for chondrocyte maturation, is one of the major factors that regulate Col10a1 expression via interaction with its tandem repeat Runx2 binding sites. Interestingly, by yeast one-hybrid approach using this cis-enhancer as bait, we identified p53 related proteins as candidate factors that may contribute to the regulation of Col10a1 expression. We have performed Real-time RT-PCR to examine p63 and Runx2 expression in MCT cells, a cell model that shows significant upregulation of Col10a1 upon growth arrest. Both p63 and Runx2 showed around 2-fold upregulation in hypertrophic MCT cells. These data suggest that P63 may collaborate with Runx2 and together regulate Col10a1 expression during chondrocyte maturation. To further explore the putative function of P63 during skeletal development, we have successfully established transgenic mouse lines in which HA and Flag tagged human TAP63α cDNA (the longest P63 isotype) is driven by previously described hypertrophic chondrocyte-specific Col10a1 control element (Col10a1-TAP63α). By phenotypic analysis of these transgenic mice during different developmental stages, we will be able to define the consequence and the potential mechanism of P63 on skeletal development and skeletal disorders.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4972.