Incomplete penetrance of a novel SDHD variation causing familial head and neck paraganglioma.

OBJECTIVE: Identification of variations in tumour suppressor genes encoding the tetrameric succinate dehydrogenase (SDHx) mitochondrial enzyme complex may lead to personalised therapeutic concepts for the orphan disease, familial paraganglioma (PGL) type 1-5. We undertook to determine the causative variation in a family suffering from idiopathic early-onset (22 ± 2 years) head and neck PGL by PCR and Sanger sequencing. DESIGN: Prospective genetic study. SETTING: Tertiary Referral Otolaryngology Centre. PARTICIPANTS: Twelve family members. MAIN OUTCOME MEASURES: Main outcomes were clinical analysis and SDH genotyping RESULTS AND CONCLUSIONS: A novel heterozygous c.298delA frameshift variation in exon 3 of SDH subunit D (SDHD) was associated with a paternal transmission pattern of PGL in affected family members available to the study. Family history over five generations in adulthood indicated a variable penetrance for PGL inheritance in older generations. The c.298delA variant would cause translation of a 34-residue C-terminus distal to lysine residue 99 in the predicted transmembrane domain II of the full-length sequence p.(Thr100LeufsTer35) and would affect the translation products of all protein-coding SDHD isoforms containing transmembrane topologies required for positional integration in the inner mitochondrial membrane and complex formation. These results underly the importance of genetic screening for PGL also in cases of unclear inheritance, and variation carriers should benefit from screening and lifelong follow-up.

PRKCA Overexpression Is Frequent in Young Oral Tongue Squamous Cell Carcinoma Patients and Is Associated with Poor Prognosis.

Oral tongue squamous cell carcinomas (OTSCCs) have an increasing incidence in young patients, and many have an aggressive course of disease. The objective of this study was to identify candidate prognostic protein markers associated with early-onset OTSCC. We performed an exploratory screening for differential protein expression in younger (≤45 years) versus older (>45 years) OTSCC patients in The Cancer Genome Atlas (TCGA) cohort (n = 97). Expression of candidate markers was then validated in an independent Austrian OTSCC patient group (n = 34) by immunohistochemistry. Kaplan-Meier survival estimates were computed, and genomic and mRNA enrichment in silico analyses were performed. Overexpression of protein kinase C alpha (PRKCA) was significantly more frequent among young patients of both the TCGA (p = 0.0001) and the Austrian cohort (p = 0.02), associated with a negative anamnesis for alcohol consumption (p = 0.009) and tobacco smoking (p = 0.02) and poorer overall survival (univariate p = 0.02, multivariate p< 0.01). Within the young subgroup, both overall and disease-free survival were significantly decreased in patients with PRKCA overexpression (both p < 0.001). TCGA mRNA enrichment analysis revealed 332 mRNAs with significant differential expression in PRKCA-upregulated versus PRKCA-downregulated OTSCC (all FDR ≤ 0.01). Our findings suggest that PRKCA overexpression may be a hallmark of a novel molecular subtype of early-onset alcohol- and tobacco-negative high-risk OTSCC. Further analysis of the molecular PRKCA interactome may decipher the underlying mechanisms of carcinogenesis and clinicopathological behavior of PRKCA-overexpressing OTSCC.

High Prevalence of MYO6 Variants in an Austrian Patient Cohort With Autosomal Dominant Hereditary Hearing Loss.

INTRODUCTION: Genetic hearing loss (HL) is often monogenic. Whereas more than half of autosomal recessive (AR) cases in Austria are caused by mutations in a single gene, no disproportionately frequent contributing genetic factor has been identified in cases of autosomal dominant (AD) HL. The genetic characterization of HL continues to improve diagnosis, genetic counseling, and lays a foundation for the development of personalized medicine approaches. METHODS: Diagnostic HL panel screening was performed in an Austrian multiplex family with AD HL, and segregation was tested with polymerase chain reaction and Sanger sequencing. In an independent approach, 18 unrelated patients with AD HL were screened for causative variants in all known HL genes to date and segregation was tested if additional family members were available. The pathogenicity of novel variants was assessed based on previous literature and bioinformatic tools such as prediction software and protein modeling. RESULTS: In six of the 19 families under study, candidate pathogenic variants were identified in MYO6, including three novel variants (p.Gln441Pro, p.Ser612Tyr, and p.Gln650ValfsTer7). Some patients carried more than one likely pathogenic variant in known deafness genes. CONCLUSION: These results suggest a potential high prevalence of MYO6 variants in Austrian cases of AD HL. The presence of multiple rare HL variants in some patients highlights the relevance of considering multiple-hit diagnoses for genetic counseling and targeted therapy design.

A novel proline substitution (Arg201Pro) in alpha helix 8 of TMEM98 causes autosomal dominant nanophthalmos-4, closed angle glaucoma and attenuated visual acuity.

Nanophthalmos-4 is a rare autosomal dominant disorder caused by two known variations in TMEM98. An Austrian Caucasian pedigree was identified suffering from nanophthalmos and late onset angle-closure glaucoma and premature loss of visual acuity. Whole exome sequencing identified segregation of a c.602G > C transversion in TMEM98 (p.Arg201Pro) as potentially causative. A protein homology model generated showed a TMEM98 structure comprising α4, α5/6, α7 and α8 antiparallel helix bundles and two predicted transmembrane domains in α1 and α7 that have been confirmed in vitro. Both p.Arg201Pro and the two missense variations representing proline insertions identified previously to cause nanophthalmos-4 (p.Ala193Pro and p.His196Pro) are located in the charge polarized helix α8 (p.183-p210). Stability of the C-terminal alpha helical structure of TMEM98 is therefore essential to prevent the development of human nanophthalmos-4. Precise molecular diagnosis could lead to the development of tailored therapies for patients with orphan ocular disease.

A Novel Variant in the TBC1D24 Lipid-Binding Pocket Causes Autosomal Dominant Hearing Loss: Evidence for a Genotype-Phenotype Correlation.

Background: Hereditary hearing loss is a disorder with high genetic and allelic heterogeneity. Diagnostic screening of candidate genes commonly yields novel variants of unknown clinical significance. TBC1D24 is a pleiotropic gene associated with recessive DOORS syndrome, epileptic encephalopathy, myoclonic epilepsy, and both recessive and dominant hearing impairment. Genotype-phenotype correlations have not been established to date but could facilitate diagnostic variant assessment and elucidation of pathomechanisms. Methods and Results: Whole-exome and gene panel screening identified a novel (c.919A>C; p.Asn307His) causative variant in TBC1D24 in two unrelated Caucasian families with Autosomal dominant (AD) nonsyndromic late-onset hearing loss. Protein modeling on the Drosophila TBC1D24 ortholog Skywalker crystal structure showed close interhelix proximity (6.8Å) between the highly conserved residue p.Asn307 in α18 and the position of the single known pathogenic dominant variation (p.Ser178Leu) in α11 that causes a form of deafness with similar clinical characteristics. Conclusion: Genetic variants affecting two polar hydrophilic residues in neighboring helices of TBC1D24 cause AD nonsyndromic late-onset hearing loss. The spatial proximity of the affected residues suggests the first genotype-phenotype association in TBC1D24-related disorders. Three conserved residues in α18 contribute to the formation of a functionally relevant cationic phosphoinositide binding pocket that regulates synaptic vesicle trafficking which may be involved in the molecular mechanism of disease.

Overexpression of LAPTM4B-35 is a negative prognostic factor in head and neck squamous cell carcinoma.

Overexpression of LAPTM4B-35 (lysosomal-associated transmembrane protein 4ß-35) is associated with a poor prognosis in numerous malignant tumours. Expression patterns and effects of LAPTM4B-35 on head and neck squamous cell carcinomas (HNSCC) are unknown. The aim of this study was to investigate the prognostic relevance of LAPTM4B-35 in HNSCC. Tissue microarrays were constructed with primary tumours and associated lymph node metastases isolated from 127 patients. The expression of LAPTM4B-35 was investigated by immunohistochemistry and the results were correlated with survival data. LAPTM4B-35 in the primary tumour was highly expressed in 47.2% of the patients (60/127). LAPTM4B-35 expression was significantly associated with tumour stage. Moreover, overexpression of LAPTM4B-35 correlated with a significantly worse disease-free survival (10.23 years vs. not reached) and a higher recurrence rate (40.7% vs. 25%). High expression of LAPTM4B-35 in lymph node metastasis was found in 29.2% of cases. In 19.4% of cases, high LAPTM4B-35 expression was observed in both the primary tumour and corresponding lymph node metastases. In conclusion, our data indicates that overexpression of LAPTM4B-35 is associated with poor prognosis and may therefore serve as a new prognostic marker in HNSCC.

Spectrum of Novel Hereditary Hemorrhagic Telangiectasia Variants in an Austrian Patient Cohort.

OBJECTIVES: Hereditary hemorrhagic telangiectasia (HHT) is a rare autosomal dominant genetic disorder characterized by pathogenic blood vessel development and maintenance. HHT type 1 (HHT1) and type 2 (HHT2) are caused by variants in endoglin (ENG) and activin receptor-like kinase-1 (ACVRL1), respectively. The aim of this study was to identify the spectrum of pathogenic variants in ENG and ACVRL1 in Austrian HHT families. METHODS: In this prospective study, eight Austrian HHT families were screened for variants in ENG and ACVRL1 by polymerase chain reaction amplification and sequencing of DNA isolated from peripheral blood. RESULTS: Heterozygous variants were identified in all families under study. HHT1 was caused by a novel c.816+1G>A splice donor variant, a novel c.1479C>A nonsense (p.Cys493X) variant and a published c.1306C>T nonsense (p.Gln436X) variant in ENG. Variants found in ACVRL1 were novel c.200G>C (p.Arg67Pro) and known c.772G>A (p.Gly258Ser) missense variants in highly conserved residues, a known heterozygous c.100dupT frameshift (p.Cys34Leufs*4) and the known c.1204G>A missense (p.Gly402Ser) and c.1435C>T nonsense (p.Arg479X) variants as causes of HHT2. CONCLUSION: Novel and published variants in ENG (37.5%) and ACVRL1 (62.5%) were exclusively identified as the cause of HHT in an Austrian patient cohort. Identification of novel causative genetics variants should facilitate the development of tailored therapeutical applications in the future treatment of autosomal dominant HHT.

Identification of a rare COCH mutation by whole-exome sequencing : Implications for personalized therapeutic rehabilitation in an Austrian family with non-syndromic autosomal dominant late-onset hearing loss.

BACKGROUND: Non-syndromic autosomal dominant hearing impairment is characteristically postlingual in onset. Genetic diagnostics are essential for genetic counselling, disease prognosis and understanding of the molecular mechanisms of disease. To date, 36 causative genes have been identified, many in only individual families. Gene selection for genetic screening by traditional methods and genetic diagnosis in autosomal dominant patients has therefore been fraught with difficulty. Whole-exome sequencing provides a powerful tool to analyze all protein-coding genomic regions in parallel, thus allowing the comprehensive screening of all known genes and associated alterations. METHODS: In this study, a previously undiagnosed late-onset progressive autosomal dominant hearing loss in an Austrian family was investigated by means of whole-exome sequencing. Results were confirmed by Sanger sequencing. RESULTS: A previously described c.151C>T missense (p.Pro51Ser) mutation in the LCCL (limulus factor C, cochlin, late gestation lung protein Lgl1) domain of the cochlin gene (COCH) was identified as causative and segregated with disease in five members of the family. Molecular diagnostics led to the decision to perform cochlear implantation in an index patient who subsequently showed excellent postoperative auditory performance. The c.151C>T mutation was not found in 18 screened Austrian families with autosomal dominant hearing loss but was represented alongside other known pathogenic mutant COCH alleles in the Genome Aggregation Database (gnomAD) in European populations. A combined allele frequency of 0.000128 implies an orphan disease frequency for COCH-induced hearing loss of 1:3900 in Europe. CONCLUSIONS: Exome sequencing successfully resolved the genetic diagnosis in a family suffering from autosomal dominant hearing impairment and allowed prediction of purported auditory outcome after cochlear implantation in an index patient. Personalized treatment approaches based on the molecular mechanisms of disease may become increasingly important in the future.

Whole-exome sequencing to identify the cause of congenital sensorineural hearing loss in carriers of a heterozygous GJB2 mutation.

Bi-allelic variations in the gap junction protein beta-2 (GJB2) gene cause up to 50% of cases of newborn hearing loss. Heterozygous pathogenic GJB2 variations are also fivefold overrepresented in idiopathic patient groups compared to the normal-hearing population. Whether hearing loss in this group is due to unidentified additional variations within GJB2 or variations in other deafness genes is unknown in most cases. Whole-exome sequencing offers an effective approach in the search for causative variations in patients with Mendelian diseases. In this prospective genetic cohort study, we initially investigated a family of Turkish origin suffering from congenital autosomal recessive hearing loss. An index patient and his normal-hearing father, both bearing a single heterozygous pathogenic c.262G>T (p.Ala88Ser) GJB2 transversion as well as the normal-hearing mother were investigated by means of whole-exome sequencing. Subsequently the genetic screening was extended to a hearing-impaired cohort of 24 families of Turkish origin. A homozygous missense c.5492G>T transversion (p.Gly1831Val) in the Myosin 15a gene, previously linked to deafness, was identified as causative in the index family. This very rare variant is not listed in any population in the Genome Aggregation Database. Subsequent screening of index patients from additional families of Turkish origin with recessive hearing loss identified the c.5492G>T variation in an additional family. Whole-exome sequencing may effectively identify the causes of idiopathic hearing loss in patients bearing heterozygous GJB2 variations.

A Novel Mutation in SLC26A4 Causes Nonsyndromic Autosomal Recessive Hearing Impairment.

BACKGROUND: Heterozygous mutations in GJB2 (MIM: 121011) encoding the gap junction protein connexin 26 are overrepresented in patient groups suffering from nonsyndromic sensorineural hearing impairment (HI) implying the involvement of additional genetic factors. Mutations in SLC26A4 (MIM: 605646), encoding the protein pendrin can cause both Pendred syndrome and autosomal recessive, nonsyndromic HI locus 4 type sensorineural HI (MIM: 600791). OBJECTIVES: Aim of this study was to investigate the role of SLC26A4 coding mutations in a nonsyndromic hearing impairment (NSHI) patient group bearing heterozygous GJB2 35delG mutations. DESIGN: We analyzed the 20 coding exons of SLC26A4 in a group of patients (n = 15) bearing heterozygous 35delG mutations and exclusively suffering from congenital HI. RESULTS: In a case of bilateral congenital hearing loss we identified a rare, novel SLC26A4 exon 2 splice donor mutation (c.164+1delG) predicted to truncate pendrin in the first cytoplasmic domain, as a compound heterozygote with the pathogenic missense mutation c.1061T>C (p.354F>S; rs111033243). CONCLUSIONS: Screening for SLC26A4 mutations may identify the genetic causes of hearing loss in patients bearing heterozygous mutations in GJB2. HYPOTHESIS: SLC26A4 coding mutations are genetic causes for nonsyndromic HI in patients bearing heterozygous GJB2 35delG mutations.

The role of alternative GJB2 transcription in screening for neonatal sensorineural deafness in Austria.

CONCLUSION: Alterations within a novel putative Exon 1a within the gap junction beta 2 (GJB2) gene may play a role in the development of genetic hearing impairment in Austria. OBJECTIVES: Mutations in the GJB2 gene are the most common cause of hereditary sensorineural deafness. Genome-wide screening for alternative transcriptional start sites in the human genome has revealed the presence of an additional GJB2 exon (E1a). This study tested the hypothesis of whether alternative GJB2 transcription involving E1a may play a role in the development of congenital sensorineural deafness in Austria. METHODS: GJB2 E1a and flanking regions were sequenced in randomized normal hearing control subjects and three different patient groups with non-syndromic hearing impairment (NSHI), and bioinformatic analysis was performed. Statistical analysis of disease association was carried out using the Cochran-Armitage test for trend. RESULTS: A single change 2410 bp proximal to the translational start site (c.-2410T > C, rs7994748, NM_004004.5:c.-23 + 792T > C) was found to be significantly associated with the common c.35delG GJB2 mutation (p = .009). c.35delG in combination with c.-2410CC occurred at a 6.9-fold increased frequency compared to the control group. Additionally, one patient with idiopathic congenital hearing loss was found to be homozygous c.-2410CC.

PlGF and VEGF-A Regulate Growth of High-Risk MYCN-Single Copy Neuroblastoma Xenografts via Different Mechanisms.

Neuroblastoma (NB) is the most common extracranial solid tumor of childhood and is a rapidly growing, highly-vascularized cancer. NBs frequently express angiogenic factors and high tumor angiogenesis has been associated with poor outcomes. Placental growth factor (PlGF) is an angiogenic protein belonging to the vascular endothelial growth factor (VEGF) family and is up-regulated mainly in pathologic conditions. Recently, PlGF was identified as a member of a gene expression signature characterizing highly malignant NB stem cells drawing attention as a potential therapeutic target in NB. In the present study, we sought to investigate the expression of PlGF in NB patients and the effect of PlGF inhibition on high-risk MYCN-non-amplified SK-N-AS NB xenografts. Human SK-N-AS cells, which are poorly differentiated and express PlGF and VEGF-A, were implanted subcutaneously in athymic nude mice. Treatment was done by intratumoral injection of replication-incompetent adenoviruses (Ad) expressing PlGF- or VEGF-specific short hairpin (sh)RNA, or soluble (s)VEGF receptor 2 (VEGFR2). The effect on tumor growth and angiogenesis was analyzed. High PlGF expression levels were observed in human advanced-stage NBs. Down-regulating PlGF significantly reduced NB growth in established NB xenografts by reducing cancer cell proliferation but did not suppress angiogenesis. In contrast, blocking VEGF by administration of Ad(sh)VEGF and Ad(s)VEGFR2 reduced tumor growth associated with decreased tumor vasculature. These findings suggest that PlGF and VEGF-A modulate MYCN-non-amplified NB tumors by different mechanisms and support a role for PlGF in NB biology.

The promoter mutation c.-259C>T (-3438C>T) is not a common cause of non-syndromic hearing impairment in Austria.

The objective of this study was to investigate the relevance of routine assessment of c.-259C>T in the Austrian newborn screening program. Homozygous and compound heterozygous mutations in the coding region of the human gene encoding gap junction protein GJB2 (Connexin 26) cause up to 50 % of neonatal autosomal recessive non-syndromic hearing impairment identified in Caucasian newborn screening programs. More recently, a null mutation in the GC box of the GJB2 basal promoter c.-259C>T has been described which causes hearing impairment by completely suppressing GJB2 promoter activity. We determined the occurrence of c.-259C>T in cases of non-syndromic hearing impairment lacking known pathogenic alterations in GJB2 (n = 43), a non-syndromic hearing impaired patient group (n = 15) bearing the heterozygous GJB2 mutations c.35delG, c.[79G>A];[341A>G] (p. [V27I];[E114G]), c.109G>A (p.V37I), c.154G>C (p.V52L), c.262G>T (p.A88S), c.269T>C (p.L90P) and c.551G>C (p.R184P) and in a normal hearing group lacking alterations in GJB2 (n = 50). In the analyzed groups, no occurrence of c.-259C>T was found. The c.-259C>T mutation, previously described as -3438C>T, is not a common cause of non-syndromic hearing impairment alone or together with heterozygous pathogenic GJB2 mutations that are statistically overrepresented in non-syndromic hearing impaired patient groups. Screening of newborns for c.-259C>T is therefore unlikely to be commonly found in Austrian NSHI patients but could make a significant contribution to non-syndromic hearing impairment in other populations.

Delayed auditory pathway maturation and prematurity.

BACKGROUND: Hearing loss is the most common sensory disorder in developed countries and leads to a severe reduction in quality of life. In this uncontrolled case series, we evaluated the auditory development in patients suffering from congenital nonsyndromic hearing impairment related to preterm birth. METHODS: Six patients delivered preterm (25th-35th gestational weeks) suffering from mild to profound congenital nonsyndromic hearing impairment, descending from healthy, nonconsanguineous parents and were evaluated by otoacoustic emissions, tympanometry, brainstem-evoked response audiometry, and genetic testing. All patients were treated with hearing aids, and one patient required cochlear implantation. RESULTS: One preterm infant (32nd gestational week) initially presented with a 70 dB hearing loss, accompanied by negative otoacoustic emissions and normal tympanometric findings. The patient was treated with hearing aids and displayed a gradual improvement in bilateral hearing that completely normalized by 14 months of age accompanied by the development of otoacoustic emission responses. Conclusions We present here for the first time a fully documented preterm patient with delayed auditory pathway maturation and normalization of hearing within 14 months of birth. Although rare, postpartum development of the auditory system should, therefore, be considered in the initial stages for treating preterm hearing impaired patients.

Modulating the tumor microenvironment with RNA interference as a cancer treatment strategy.

The tumor microenvironment is composed of accessory cells and immune cells in addition to extracellular matrix (ECM) components. The stromal compartment interacts with cancer cells in a complex crosstalk to support tumor development. Growth factors and cytokines produced by stromal cells support the growth of tumor cells and promote interaction with the vasculature to enhance tumor progression and invasion. The activation of autocrine and paracrine oncogenic signaling pathways by growth factors, cytokines, and proteases derived from both tumor cells and the stromal compartment is thought to play a major role in assisting tumor cells during metastasis. Consequently, targeting tumor-stroma interactions by RNA interference (RNAi)-based approaches is a promising strategy in the search for novel treatment modalities in human cancer. Recent advances in packaging technology including the use of polymers, peptides, liposomes, and nanoparticles to deliver small interfering RNAs (siRNAs) into target cells may overcome limitations associated with potential RNAi-based therapeutics. Newly developed nonviral gene delivery approaches have shown improved anticancer efficacy suggesting that RNAi-based therapeutics provide novel opportunities to elicit significant gene silencing and induce regression of tumor growth. This chapter summarizes our current understanding of the tumor microenvironment and highlights some potential targets for therapeutic intervention with RNAi-based cancer therapeutics.

A novel missense NDP mutation [p.(Cys93Arg)] with a manifesting carrier in an austrian family with Norrie disease.

Norrie disease is a rare, X-linked genetic syndrome characterized by combined congenital blindness and progressive hearing impairment. Norrie disease is caused by alterations in the NDP gene encoding the growth factor norrin that plays a key role in vascular development and stabilization of the eye, inner ear and brain. We identified a family with 3 affected deafblind males and a single female carrier presenting with a serous retinal detachment but normal hearing. Genetic analysis revealed a novel c.277T>C missense mutation causing the substitution of a hydrophobic cysteine to a hydrophilic arginine [p.(Cys93Arg)] within the highly conserved cysteine knot domain of the norrin protein. These results should expand the scope for amniocentesis and genetic testing for Norrie disease which is gaining in importance due to novel postnatal therapeutic concepts to alleviate the devastating retinal symptoms of Norrie disease.

Despite a lack of otoacoustic emission, word recognition is not seriously influenced in a TECTA DFNA8/12 family.

OBJECTIVES: Similar to other zona pellucida mutations in the alpha-tectorin (TECTA) gene, the p.Y1870C alteration in DFNA8/12 causes prelingual, nonsyndromic, autosomal dominant hearing loss. Here we investigated the effect of p.Y1870C on reverse transduction by audiometric studies in the family. METHODS: Pure tone audiometry, brainstem evoked response audiometry, the Freiburger test for speech understanding and transient evoked and distortion product otoacoustic emissions were assessed in three available affected members bearing p.Y1870C. RESULTS: Pure tone audiometry showed U-shaped curves with moderate to severe degrees of hearing impairment confirmed by brainstem evoked response audiometry. Transient evoked and distortion product otoacoustic emissions were completely absent in all affected family members whereas word recognition scores were up to 95%. CONCLUSIONS: Although the missense p.Y1870C TECTA mutation leads to complete failure of the cochlear amplifier in humans, very high speech perception scores can be achieved with appropriate therapy.

Egr-1 upregulates Siva-1 expression and induces cardiac fibroblast apoptosis.

The early growth response transcription factor Egr-1 controls cell specific responses to proliferation, differentiation and apoptosis. Expression of Egr-1 and downstream transcription is closely controlled and cell specific upregulation induced by processes such as hypoxia and ischemia has been previously linked to multiple aspects of cardiovascular injury. In this study, we showed constitutive expression of Egr-1 in cultured human ventricular cardiac fibroblasts, used adenoviral mediated gene transfer to study the effects of continuous Egr-1 overexpression and studied downstream transcription by Western blotting, immunohistochemistry and siRNA transfection. Apoptosis was assessed by fluorescence microscopy and flow cytometry in the presence of caspase inhibitors. Overexpression of Egr-1 directly induced apoptosis associated with caspase activation in human cardiac fibroblast cultures in vitro assessed by fluorescence microscopy and flow cytometry. Apoptotic induction was associated with a caspase activation associated loss of mitochondrial membrane potential and transient downstream transcriptional up-regulation of the pro-apoptotic gene product Siva-1. Suppression of Siva-1 induction by siRNA partially reversed Egr-1 mediated loss of cell viability. These findings suggest a previously unknown role for Egr-1 and transcriptional regulation of Siva-1 in the control of cardiac accessory cell death.

Targeting Cdc42 with the small molecule drug AZA197 suppresses primary colon cancer growth and prolongs survival in a preclinical mouse xenograft model by downregulation of PAK1 activity.

BACKGROUND: Rho GTPases play important roles in cytoskeleton organization, cell cycle progression and are key regulators of tumor progression. Strategies to modulate increased Rho GTPase activities during cancer progression could have therapeutic potential. METHODS: We report here the characterization of a Cdc42-selective small-molecule inhibitor AZA197 for the treatment of colon cancer that was developed based on structural information known from previously developed compounds affecting Rho GTPase activation. We investigated the effects of AZA197 treatment on RhoA, Rac1 and Cdc42 activities and associated molecular mechanisms in colon cancer cells in vitro. Therapeutic effects of AZA197 were examined in vivo using a xenograft mouse model of SW620 human colon cancer cells. After treatment, tumors were excised and processed for Ki-67 staining, TUNEL assays and Western blotting to evaluate proliferative and apoptotic effects induced by AZA197. RESULTS: In SW620 and HT-29 human colon cancer cells, AZA197 demonstrated selectivity for Cdc42 without inhibition of Rac1 or RhoA GTPases from the same family. AZA197 suppressed colon cancer cell proliferation, cell migration and invasion and increased apoptosis associated with down-regulation of the PAK1 and ERK signaling pathways in vitro. Furthermore, systemic AZA197 treatment reduced tumor growth in vivo and significantly increased mouse survival in SW620 tumor xenografts. Ki-67 staining and tissue TUNEL assays showed that both inhibition of cell proliferation and induction of apoptosis associated with reduced PAK/ERK activation contributed to the AZA197-induced therapeutic effects in vivo. CONCLUSIONS: These data indicate the therapeutic potential of the small-molecule inhibitor AZA197 based on targeting Cdc42 GTPase activity to modulate colorectal cancer growth.

A Rac1/Cdc42 GTPase-specific small molecule inhibitor suppresses growth of primary human prostate cancer xenografts and prolongs survival in mice.

Deregulated Rho GTPases Rac1 and Cdc42 have been discovered in various tumors, including prostate and Rac protein expression significantly increases in prostate cancer. The Rac and Cdc42 pathways promote the uncontrolled proliferation, invasion and metastatic properties of human cancer cells. We synthesized the novel compound AZA1 based on structural information of the known Rac1 inhibitor NSC23766. In the current study we investigated the effects of inhibition of these pathways by AZA1 on prostate tumorigenicity by performing preclinical studies using a xenograft mouse model of prostate cancer. In androgen-independent prostate cancer cells, AZA1 inhibited both Rac1 and Cdc42 but not RhoA GTPase activity in a dose-dependent manner and blocked cellular migration and proliferation. Cyclin D1 expression significantly decreased following Rac1/Cdc42 inhibition in prostate cancer cells. AZA1 treatment also down-regulated PAK and AKT activity in prostate cancer cells, associated with induction of the pro-apoptotic function of BAD by suppression of serine-112 phosphorylation. Daily systemic administration of AZA1 for 2 weeks reduced growth of human 22Rv1 prostate tumor xenografts in mice and improved the survival of tumor-bearing animals significantly. These data suggest a role of AZA1 in blocking Rac1/Cdc42-dependent cell cycle progression, cancer cell migration and increase of cancer cell apoptosis involving down-regulation of the AKT and PAK signaling pathway in prostate cancer cells. We therefore propose that a small-molecule inhibitor therapy targeting Rac1/Cdc42 Rho GTPase signaling pathways may be used as a novel treatment for patients with advanced prostate cancer.