Adnectin-drug conjugates for Glypican-3-specific delivery of a cytotoxic payload to tumors.

Tumor-specific delivery of cytotoxic agents remains a challenge in cancer therapy. Antibody-drug conjugates (ADC) deliver their payloads to tumor cells that overexpress specific tumor-associated antigens-but the multi-day half-life of ADC leads to high exposure even of normal, antigen-free, tissues and thus contributes to dose-limiting toxicity. Here, we present Adnectin-drug conjugates, an alternative platform for tumor-specific delivery of cytotoxic payloads. Due to their small size (10 kDa), renal filtration eliminates Adnectins from the bloodstream within minutes to hours, ensuring low exposure to normal tissues. We used an engineered cysteine to conjugate an Adnectin that binds Glypican-3, a membrane protein overexpressed in hepatocellular carcinoma, to a cytotoxic derivative of tubulysin, with the drug-to-Adnectin ratio of 1. We demonstrate specific, nanomolar binding of this Adnectin-drug conjugate to human and murine Glypican-3; its high thermostability; its localization to target-expressing tumor cells in vitro and in vivo, its fast clearance from normal tissues and its efficacy against Glypican-3-positive mouse xenograft models.

Role of magnetic resonance imaging in the early diagnosis of paratesticular rhabdomyosarcoma.

INTRODUCTION: Paratesticular lesions are common, and one subgroup is paratesticular rhabdomyosarcoma. The latter is a relatively uncommon (but aggressive) tumour that affects children and adolescents predominantly. Ultrasound is the first-line investigation, but can be inconclusive. Magnetic resonance imaging (MRI) can provide useful information, but its role in the diagnosis of rhabdomyosarcoma is not clear. CASE HISTORY: We report a 17-year-old male who presented with a one-month history of a rapidly enlarging, non-tender, lump in the right testicle. Urgent ultrasound of the scrotum revealed a heterogenous paratesticular mass that was hypervascular and showed calcification in the right inguinal area. MRI of the pelvis showed a solid, enhancing lesion of dimension located superior to the upper pole of the right testes and a slightly heterogeneous T2 signal, but was homogenous post-contrast. The patient underwent right radical orchidectomy, and histology results were assessed. He received chemotherapy and is being followed up. CONCLUSIONS: Improvements in imaging in addition to early surgical intervention and chemotherapy treatment are crucial to improve survival chances against rhabdomyosarcoma. Ultrasound findings for benign diseases may mimic those seen in rhabdomyosarcoma. In such cases of diagnostic uncertainty, our surgical team suggest MRI to reduce the risk of a delayed diagnosis and time to treatment.

A decision framework for prioritizing multiple management actions for threatened marine megafauna.

Resources for conserving biodiversity are invariably insufficient. This situation creates the need for transparent, systematic frameworks to help stakeholders prioritize the allocation of resources across multiple management actions. We developed a novel framework that explicitly prioritizes actions to minimize the impacts of several threats across a species' range. The framework uses a budget constraint and maximizes conservation outcomes from a set of management actions, accounting for the likelihood of the action being successfully applied and accepted by local and Indigenous communities. This approach is novel in that it integrates local knowledge and expert opinion with optimization software, thereby minimizing assumptions about likelihood of success of actions and their effectiveness. To test the framework, we used the eastern Gulf of Carpentaria and Torres Strait population of the flatback turtle, Natator depressus, as a case study. This approach allowed the framework to be applied in a data-poor context, a situation common in conservation planning. The framework identified the best set of actions to maximize the conservation of flatback eggs for scenarios with different budgets and management parameters and allowed comparisons between optimized and preselected scenarios. Optimized scenarios considered all implementable actions to explore how to best allocate resources with a specified budget and focus. Preselected scenarios were used to evaluate current allocations of funds and/or potential budget allocations suggested by different stakeholders. Scenarios that used a combination of aerial and ground strategies to reduce predation of eggs performed better than scenarios that focused only on reducing harvest of eggs. The performances of optimized and preselected scenarios were generally similar among scenarios that targeted similar threats. However, the cost-effectiveness of optimized scenarios was usually higher than that of preselected scenarios, demonstrating the value of conducting a systematic optimization approach. Our method provides a foundation for more effective conservation investments and guidance to prioritize actions within recovery plans while considering the sociopolitical and cultural context of decisions. The framework can be adapted easily to a wide range of species, geographical scales, and life stages.

Efficacy and safety of CDX-301, recombinant human Flt3L, at expanding dendritic cells and hematopoietic stem cells in healthy human volunteers.

Fms-like tyrosine kinase-3 ligand (Flt3L) uniquely binds the Flt3 (CD135) receptor expressed on hematopoietic stem cells (HSCs), early progenitor cells, immature thymocytes and steady-state dendritic cells (DCs) and induces their proliferation, differentiation, development and mobilization in the bone marrow, peripheral blood and lymphoid organs. CDX-301 has an identical amino-acid sequence and comparable biological activity to the previously tested rhuFlt3L, which ceased clinical development over a decade ago. This Phase 1 trial assessed the safety, pharmacokinetic, pharmacodynamic and immunologic profile of CDX-301, explored alternate dosing regimens and examined the impact of rhuFlt3L on key immune cell subsets. Thirty healthy volunteers received CDX-301 (1-75 µg/kg/day) over 5-10 days. One event of Grade 3 community-acquired pneumonia occurred. There were no other infections, dose-limiting toxicities or serious adverse events. CDX-301 resulted in effective peripheral expansion of monocytes, hematopoietic stem and progenitor cells and key subsets of myeloid DCs and plasmacytoid DCs, with no clear effect on regulatory T cells. These data from healthy volunteers support the potential for CDX-301, as monotherapy or in combination with other agents, in various indications including allogeneic HSC transplantation and immunotherapy, but the effects of CDX-301 will need to be investigated in each of these patient populations.

Testosterone deficiency and severity of erectile dysfunction are independently associated with reduced quality of life in men with type 2 diabetes.

Erectile dysfunction (ED) and low testosterone levels are common in men with type 2 diabetes (T2D). We have investigated the impact of testosterone on quality of life (QoL) in diabetic men with ED. Men with ED were identified within a study cohort of 355 men with T2D. All subjects completed SF-36 health and Androgen Deficiency of the Aging Male questionnaires. Total tesosterone (TT), bioavailable testosterone (BT) and sex hormone-binding globulin levels of study participants were measured and free testosterone levels were calculated (cFT). A subgroup of 126 ED patients completed the International Index of Erectile Function-5 (IIEF-5) questionnaire. Linear regression analyses were corrected for age, body mass index (BMI), glycosylated haemoglobin (HbA1c), smoking, alcohol consumption and cardiovascular disease (CVD). Total SF-36 scores significantly and positively correlated with TT levels (r = 0.219, p = 0.001), BT levels (r = 0.199, p = 0.004) and cFT levels (r = 0.185, p = 0.007) among men with ED. These trends were strengthened after adjusting for age, BMI, HbA1c, smoking, alcohol consumption and CVD (TT r = 0.359, p = 0.015; BT r = 0.354, p = 0.024 and cFT r = 0.354, p = 0.024). IIEF-5 scores significantly correlated inversely with TT (r = 0.546, p = 0.001), BT (r = 0.506, p = 0.004) and cFT levels (r = 0.532, p = 0.001). A positive linear relationship was observed between IIEF-5 scores and total SF-36 score (r = 0.491, p = 0.003). Patients who reported having ED had an average SF-36 score of 9.1% less than those without ED (p < 0.001). Lower testosterone and greater severity of ED independently correlated with poorer physical function, social function, vitality and decline in general health domains of the SF-36. This is the first study to report that testosterone deficiency and severity of ED are both independently associated with reduced QoL in men with T2D. Furthermore, ED and low testosterone are markers of poor health which impact on an individual's self-perception of their health status.

Evaluation of the pressure leak test in increasing the lifespan of flexible ureteroscopes.

INTRODUCTION: Flexible ureteroscopes are expensive and delicate instruments that are integral in the offering of a minimally invasive technique of diagnosis and treatment of urolithiasis. Published literature has identified the importance of early damage recognition in preventing frequent use of the scope that would lead to further damage and high repair and replacement costs. Our study was designed to examine the outcome of the pressure leak test on the condition of flexible ureteroscopes after every use and analysing the damage and costs of maintenance. PATIENTS AND METHODS: A prospective study was designed with two treatment groups. Group 1, 95 consecutive procedures (n = 95) of flexible ureterorenoscopy and laser fragmentation of renal calculi were performed with ACMI DUR 8, (a scope with no in-built leak test facility). This was compared against group 2, where 98 procedures of laser fragmentation of renal calculi (n = 98) were performed using Storz Flex X(2) Ureteroscopes (with a in-built leak test facility). All scopes in Group 2 were tested for pressure leak after every procedure and the outcome of the tests recorded. RESULTS: Both groups were comparable for grade of surgeon; stone location, size & number; access sheath usage and duration of lasering. In Group 1, there were seven scope damages resulting in repairs/replacement amounting to costs $46264.40 (7.1% damage). In Group 2, three scopes revealed a positive pressure leak test, implying damage with repair costs of $9952.80 (3.1% damage) (p < 0.05). Significant cost savings and reduction in downtime were made in Group 2. CONCLUSIONS: Pressure leak testing following flexible ureterorenoscopy helped to significantly control costs of maintenance and repair. Newer scopes should have a leak testing mechanism as it prevents further detrimental damage to the scope, build-up of repair costs are avoided and there is an increase in the longevity of these delicate instruments.

Guiding principles for the improved governance of port and shipping impacts in the Great Barrier Reef.

The Great Barrier Reef (GBR) region of Queensland, Australia, encompasses a complex and diverse array of tropical marine ecosystems of global significance. The region is also a World Heritage Area and largely within one of the world's best managed marine protected areas. However, a recent World Heritage Committee report drew attention to serious governance problems associated with the management of ports and shipping. We review the impacts of ports and shipping on biodiversity in the GBR, and propose a series of guiding principles to improve the current governance arrangements. Implementing these principles will increase the capacity of decision makers to minimize the impacts of ports and shipping on biodiversity, and will provide certainty and clarity to port operators and developers. A 'business as usual' approach could lead to the GBR's inclusion on the List of World Heritage in Danger in 2014.

Urological complications of inguinal hernia surgery.

BACKGROUND AND AIMS: A systematic review of the literature is presented with regard to urological complications resulting from inguinal hernia surgery. Considering the amount of inguinal hernia operations performed, the resulting complications, which may be urological in presentation, have potential late irreversible and medico-legal implications. METHODS AND RESULTS: A Pubmed search of 'urological' 'complications' and 'inguinal hernia surgery' was carried out and clinical practice was also taken into consideration. DISCUSSION: Approximately 75% of hernias occur in the groin; two-third of these are indirect and about one-third direct. Most of these repairs are carried out by the general surgeons and any complication, including urological, are often initially managed by the operating general surgeon. Often a urological opinion is sought late for conditions which may be reversible. We present potential urological complications, their presenting features and management. CONCLUSION: Recognition, timely referral and appropriate treatment of urological complications after hernia surgery are necessary to avoid potential consequences and long-term morbidity.

Phantom shocks unmasked: clinical data and proposed mechanism of memory reactivation of past traumatic shocks in patients with implantable cardioverter defibrillators.

BACKGROUND: Implantable cardioverter defibrillators (ICD), despite an unequivocal clinical benefit, are known to have a complex psychosocial impact on the patients. ICD shocks and the resultant psychobiological changes are known to contribute to increased levels of anxiety, depression, and post-shock stress symptoms in these patients. Phantom shock is a patient-reported perception of an ICD shock in the absence of any actual shock; however, its pathophysiological understanding is poor. METHODS: A retrospective chart review of the University hospital ICD patients' database from June 2006 to April 2010 was conducted. A total of 38 patients with documented phantom shocks as cases and 76 age- and sex-matched patients with no phantom shocks as controls were selected from the database. Patient characteristics were analyzed for their potential association with the occurrence of phantom shocks. RESULTS: Phantom shock patients had higher prevalence of documented depression (31.6%), anxiety (23.7%), and cocaine use (42.1%). Additionally, patients who had previous ICD shock storms were more likely to have phantom shocks (39.5%; p = 0.001). More importantly, no phantom shocks were reported in patients who did not receive defibrillation threshold testing or past ICD shock storms. CONCLUSIONS: Phantom shocks are primarily observed in ICD patients who had prior exposure to traumatic device shocks and are more common in patients with a history of depression, anxiety, or substance abuse. A pathophysiological mechanism is proposed as a guide to potential prevention.

Propofol's effects on phagocytosis, proliferation, nitrate production, and cytokine secretion in pressure-stimulated microglial cells.

BACKGROUND: Intracranial hypertension complicates severe traumatic brain injury frequently and might be associated with poor outcomes. Traumatic brain injury induces a neuroinflammatory response by microglial activation and upregulation of proinflammatory cytokines, such as interleukin-1ß, tumor necrosis factor alpha, and interleukin-6. To elucidate the effect of increased intracranial pressure on microglial function, we studied the effects of increased extracellular pressure on primary human microglial cell phagocytosis, proliferation, cytokine secretion, and total nitrate production. In addition, because many patients receive propofol during anesthesia or intensive care unit sedation, we evaluated whether propofol alters the effects of pressure. METHODS: Human microglial cells were pretreated with (2.5-20 µg/mL) propofol or Intralipid as a vehicle control were incubated at ambient atmospheric pressure or at 15 or 30 mm Hg increased pressure for 2 h for phagocytosis assays or 24 h for proliferation, cytokine secretion, and total nitrate production studies. Phagocytosis was determined by incorporation of intracellular fluorescent latex beads. Tumor necrosis factor alpha, interleukin-1ß, and interleukin-6 were assayed by sandwich enzyme-linked immunosorbent assay and total nitrate by Greiss reagent. RESULTS: Increased extracellular pressure stimulated phagocytosis versus untreated microglial cells or cells treated with an Intralipid vehicle control. Propofol also stimulated microglial phagocytosis at ambient pressure. Increased pressure, however, decreased phagocytosis in the presence of propofol. Pressure also increased microglial tumor necrosis factor-α and interleukin-1ß secretion and propofol pretreatment blocked the pressure-stimulated effect. Interleukin-6 production was not altered either by pressure or by propofol. Pressure also induced total nitrate secretion, and propofol pretreatment decreased basal as well as pressure-induced microglial nitrate production. CONCLUSION: Extracellular pressures consistent with increased intracranial pressure after a head injury activate inflammatory signals in human primary microglial cells in vitro, stimulating phagocytosis, proliferation, tumor necrosis factor-α, interleukin-1ß, and total nitrate secretion but not affecting interleukin-6. Such inflammatory events may contribute to the worsened prognosis of traumatic brain injury after increased intracranial pressure. Because propofol alleviated these potentially proinflammatory effects, these results suggest that the inflammatory cascade activated by intracranial pressure might be targeted by propofol in patients with increased intracranial pressure after traumatic brain injury.

Adnectin CT-322 inhibits tumor growth and affects microvascular architecture and function in Colo205 tumor xenografts.

Antiangiogenesis has become a promising pillar in modern cancer therapy. This study investigates the antiangiogenic effects of the PEGylated Adnectin™, CT-322, in a murine Colo-205 xenograft tumor model. CT-322 specifically binds to and blocks vascular endothelial growth factor receptor (VEGFR-2). Adnectins are a novel class of targeted biologics engineered from the 10th domain of human fibronectin. CT-322 treated tumors exhibited a significant reduction in tumor growth of 69%, a 2.8 times lower tumor surface area and fewer necrotic areas. Control tumors showed a 2.36-fold higher microvessel density (MVD) and a 2.42 times higher vessel volume in corrosion casts. The vascular architecture in CT-322-treated tumors was characterized by a strong normalization of vasculature. This was quantified in corrosion casts of CT-322 treated tumors in which the intervascular distance (a reciprocal parameter indicative of vessel density) and the distance between two consecutive branchings were assessed, with these distances being 2.21 times and 2.37 times greater than in controls, respectively. Fluorescence molecular tomography (FMT) equally affirmed the inhibitory effects of CT-322 on tumor vasculature as indicated by a 60% reduction of the vascular probe, AngioSense, accumulating in tumor tissue, as a measurement of vascular permeability. Moreover, AngioSense accumulation was reduced as early as 24 h after starting treatment. The sum of these effects on tumor vasculature illustrates the anti-angiogenic mechanism underlying the antitumor activity of CT-322 and provides support for further evaluation of this Adnectin in combinatorial strategies with standard of care therapies.

A fibronectin scaffold approach to bispecific inhibitors of epidermal growth factor receptor and insulin-like growth factor-I receptor.

Engineered domains of human fibronectin (Adnectins™) were used to generate a bispecific Adnectin targeting epidermal growth factor receptor (EGFR) and insulin-like growth factor-I receptor (IGF-IR), two transmembrane receptors that mediate proliferative and survival cell signaling in cancer. Single-domain Adnectins that specifically bind EGFR or IGF-IR were generated using mRNA display with a library containing as many as 10 ( 13) Adnectin variants. mRNA display was also used to optimize lead Adnectin affinities, resulting in clones that inhibited EGFR phosphorylation at 7 to 38 nM compared to 2.6 µM for the parental clone. Individual, optimized, Adnectins specific for blocking either EGFR or IGF-IR signaling were engineered into a single protein (EI-Tandem Adnectin). The EI-Tandems inhibited phosphorylation of EGFR and IGF-IR, induced receptor degradation, and inhibited down-stream cell signaling and proliferation of human cancer cell lines (A431, H292, BxPC3 and RH41) with IC 50 values ranging from 0.1 to 113 nM. Although Adnectins bound to EGFR at a site distinct from those of anti-EGFR antibodies cetuximab, panitumumab and nimotuzumab, like the antibodies, the anti-EGFR Adnectins blocked the binding of EGF to EGFR. PEGylated EI-Tandem inhibited the growth of both EGFR and IGF-IR driven human tumor xenografts, induced degradation of EGFR, and reduced EGFR phosphorylation in tumors. These results demonstrate efficient engineering of bispecific Adnectins with high potency and desired specificity. The bispecificity may improve biological activity compared to monospecific biologics as tumor growth is driven by multiple growth factors. Our results illustrate a technological advancement for constructing multi-specific biologics in cancer therapy.

The utility of pre-residency standardized tests for anesthesiology resident selection: the place of United States Medical Licensing Examination scores.

BACKGROUND: The resident selection process could be improved if United States Medical Licensing Examination (USMLE) scores obtained during residency application were found to predict success on the American Board of Anesthesiology (ABA) written examination (part 1). In this study, we compared USMLE performance during medical school to anesthesiology residency standardized examination performance. METHODS: Sixty-nine anesthesiology residents' USMLE, ABA/American Society of Anesthesiologists (ASA) In-Training Examination, and ABA written board examination (part 1) scores were compared. Linear regression, adjusted Pearson partial correlation, multiple regression, and analysis of variance were used to cross-correlate pre-residency and intra-residency scores. Residents' school of medicine location and year of graduation were noted. RESULTS: Both USMLE step 1 and step 2 Clinical Knowledge examinations correlated significantly with all intra-residency standardized tests. Averaged step 1 and step 2 USMLE score correlated to ABA written examination (part 1) score with a slope of 0.72 and r of 0.48 (P = 0.001). CONCLUSIONS: The USMLE is a significant predictor of residency ABA/ASA In-Training Examination and ABA written examination performance in anesthesiology. Our program has significantly increased its average written board examination performance while increasing the relative importance of USMLE in resident selection.

Rapid assessment of risks to a mobile marine mammal in an ecosystem-scale marine protected area.

Ecosystem-scale networks of marine protected areas (MPAs) are important conservation tools, but their effectiveness is difficult to quantify in a time frame appropriate to species conservation because of uncertainties in the data available. The dugong (Dugong dugon) is a mobile marine species that occurs in shallow inshore waters of an ecosystem-scale network of MPAs (the Great Barrier Reef World Heritage Area [GBRWHA]). We developed a rapid approach to assess risk to dugongs in the region and evaluate options to ameliorate that risk. We used expert opinion and a Delphi technique to identify and rank 5 human factors with the potential to adversely affect dugongs and their sea grass habitats: netting, indigenous hunting, trawling, vessel traffic, and poor-quality terrestrial runoff. We then quantified and compared the distribution of these factors with a spatially explicit model of dugong distribution. We estimated that approximately 96% of habitat of high conservation value for dugongs in the GBRWHA is at low risk from human activities. Using a sensitivity analysis, we found that to decrease risk, commercial netting or indigenous hunting had to be reduced in remote areas and the effects of vessel traffic, terrestrial runoff, and commercial netting had to be reduced in urban areas. This approach enabled us to compare and rank risks so as to identify the most severe risks and locate specific sites that require further management attention.

Near lethal art--transorbital brain injury.

Penetrative transorbital injuries put intracranial structures in peril. We present one such case where a low velocity transorbital injury resulted in traumatic temporal lobe injury, but with full recovery. Clinicians should be vigilant of intracranial complications of transorbital injuries.

First-in-human evaluation of anti von Willebrand factor therapeutic aptamer ARC1779 in healthy volunteers.

BACKGROUND: ARC1779 is a therapeutic aptamer antagonist of the A1 domain of von Willebrand Factor (vWF), the ligand for receptor glycoprotein 1b on platelets. ARC1779 is being developed as a novel antithrombotic agent for use in patients with acute coronary syndromes. METHODS AND RESULTS: This was a randomized, double-blind, placebo-controlled study in 47 healthy volunteers of doses of ARC1779 from 0.05 to 1.0 mg/kg. Pharmacodynamic effects were measured by an ELISA for free vWF A1 binding sites and by a platelet function analyzer. In terms of pharmacokinetics, the concentration-time profile of ARC1779 appeared monophasic. The observed concentration and area under the curve were dose proportional. The mean apparent elimination half-life was approximately 2 hours, and mean residence time was approximately 3 hours. The mean apparent volumes of distribution (at steady state and during terminal phase) were approximately one half the blood volume, suggesting that ARC1779 distribution is in the central compartment. The mean clearance ranged from approximately 10% to approximately 21% of the glomerular filtration rate, suggesting that renal filtration may not be a major mechanism of clearance of ARC1779. Inhibition of vWF A1 binding activity was achieved with an EC(90) value of 2.0 mug/mL (151 nmol/L) and of platelet function with an EC(90) value of 2.6 mug/mL (196 nmol/L). ARC1779 was generally well tolerated, and no bleeding was observed. Adverse events tended to be minor and not dose related. CONCLUSIONS: This is the first-in-human evaluation of a novel aptamer antagonist of vWF. ARC1779 produced dose- and concentration-dependent inhibition of vWF activity and platelet function with duration of effect suitable for the intended clinical use in acute coronary syndromes.

Phylogeography of the olive sea snake, Aipysurus laevis (Hydrophiinae) indicates Pleistocene range expansion around northern Australia but low contemporary gene flow.

Pleistocene sea-level fluctuations profoundly changed landmass configurations around northern Australia. The cyclic emergence of the Torres Strait land bridge and concomitant shifts in the distribution of shallow-water marine habitats repeatedly sundered east and west coast populations. These biogeographical perturbations invoke three possible scenarios regarding the directions of interglacial range expansion: west to east, east to west, or bidirectional. We evaluated these scenarios for the olive sea snake, Aipysurus laevis, by exploring its genetic structure around northern Australia based on 354 individuals from 14 locations in three regions (Western Australia, WA; Gulf of Carpentaria, GoC; Great Barrier Reef, GBR). A 726-bp fragment of the mitochondrial DNA ND4 region revealed 41 variable sites and 38 haplotypes, with no shared haplotypes among the three regions. Population genetic structure was strong overall, phiST=0.78, P<0.001, and coalescent analyses revealed no migration between regions. Genetic diversity was low in the GBR and GoC and the genetic signatures of these regions indicated range or population expansions consistent with their recent marine transgressions around 7000 years ago. By contrast, genetic diversity on most WA reefs was higher and there were no signals of recent expansion events on these reefs. Phylogenetic analyses indicated that GBR and GoC haplotypes were derived from WA haplotypes; however, statistical parsimony suggested that recent range expansion in the GBR-GoC probably occurred from east coast populations, possibly in the Coral Sea. Levels of contemporary female-mediated gene flow varied within regions and reflected potential connectivity among populations afforded by the different regional habitat types.

Repetitive deformation activates focal adhesion kinase and ERK mitogenic signals in human Caco-2 intestinal epithelial cells through Src and Rac1.

Intestinal epithelial cells are subject to repetitive deformation during peristalsis and villous motility, whereas the mucosa atrophies during sepsis or ileus when such stimuli are abnormal. Such repetitive deformation stimulates intestinal epithelial proliferation via focal adhesion kinase (FAK) and extracellular signal-regulated kinases (ERK). However, the upstream mediators of these effects are unknown. We investigated whether Src and Rac1 mediate deformation-induced FAK and ERK phosphorylation and proliferation in human Caco-2 and rat IEC-6 intestinal epithelial cells. Cells cultured on collagen-I were subjected to an average 10% cyclic strain at 10 cycles/min. Cyclic strain activated Rac1 and induced Rac1 translocation to cell membranes. Mechanical strain also induced rapid sustained phosphorylation of c-Src at Tyr(418), Rac1 at Ser(71), FAK at Tyr(397) and Tyr(576), and ERK1/2 at Thr(202)/Tyr(204). The mitogenic effect of cyclic strain was blocked by inhibition of Src (PP2 or short interfering RNA) or Rac1 (NSC23766). Src or Rac1 inhibition also prevented strain-induced FAK phosphorylation at Tyr(576) and ERK phosphorylation but not FAK phosphorylation at Tyr(397). Reducing FAK using short interfering RNA blocked strain-induced mitogenicity and attenuated ERK phosphorylation but not Src or Rac1 phosphorylation. Src inhibition blocked strain-induced Rac1 phosphorylation, but Rac inhibition did not alter Src phosphorylation. Transfection of a two-tyrosine phosphorylation-deficient FAK mutant Y576F/Y577F prevented activation of cotransfected myc-ERK2 by cyclic strain. Repetitive deformation induced by peristalsis or villus motility may support the gut mucosa by a pathway involving Src, Rac1, FAK, and ERK. This pathway may present important targets for interventions to prevent mucosal atrophy during prolonged ileus or fasting.