Scalable culture techniques to generate large numbers of purified human Schwann cells for clinical trials in human spinal cord and peripheral nerve injuries

OBJECTIVE

Schwann cells (SCs) have been shown to play an essential role in axon regeneration in both peripheral nerve injuries (PNIs) and spinal cord injuries (SCIs). The transplantation of SCs as an adjunctive therapy is currently under investigation in human clinical trials due to their regenerative capacity. Therefore, a reliable method for procuring large quantities of SCs from peripheral nerves is necessary. This paper presents a well-developed, validated, and optimized manufacturing protocol for clinical-grade SCs that are compliant with Current Good Manufacturing Practices (CGMPs).

METHODS

The authors evaluated the SC culture manufacturing data from 18 clinical trial participants who were recruited for autologous SC transplantation due to subacute SCI (n = 7), chronic SCI (n = 8), or PNIs (n = 3). To initiate autologous SC cultures, a mean nerve length of 11.8 ± 3.7 cm was harvested either from the sural nerve alone (n = 17) or with the sciatic nerve (n = 1). The nerves were digested with enzymes and SCs were isolated and further expanded in multiple passages to meet the dose requirements for transplantation.

RESULTS

An average yield of 87.2 ± 89.2 million cells at P2 and 150.9 ± 129.9 million cells at P3 with high viability and purity was produced. Cell counts and rates of expansion increased with each subsequent passage from P0 to P3, with the largest rate of expansion between P2 and P3. Larger harvest nerve lengths correlated significantly with greater yields at P0 and P1 (p < 0.05). In addition, a viability and purity above 90% was sustained throughout all passages in nearly all cell products.

CONCLUSIONS

This study presents reliable CGMP-compliant manufacturing methods for autologous SC products that are suitable for regenerative treatment of patients with SCI, PNI, or other conditions.

Osteoporosis: A Small-Group Case-Based Learning Activity

INTRODUCTION

Osteoporosis is the most common bone disease in the world. Approximately 50% of women and 20% of men over 50 will suffer an osteoporosis-related fracture. Future health care providers must be equipped to prevent, recognize, and treat osteoporosis-related fractures.

METHODS

To supplement instruction on osteoporosis, we designed a case-based session. Groups of 10-12 second-year medical students worked with a single facilitator in a roundtable discussion. The 120-minute session integrated foundational sciences (pathology, physiology, pharmacology) and clinical disciplines (clinical skills, radiology, geriatrics, evidence-based medicine). Knowledge gains were assessed by performance on nine session-relevant multiple-choice questions (MCQs) on the final exam. Student satisfaction was assessed by an anonymous postsession survey.

RESULTS

There were 121 students that participated, and their average performance on nine session-relevant final exam MCQs was 84%. After removal of a single outlier MCQ (15% correct), average performance on the remaining eight MCQs was 93%. A total of 107 students (88%) responded to the postsession survey. On a 5-point Likert scale, 101 of 107 students (94%) agreed or strongly agreed with the statement "The basic science-clinical combination lecture on osteoporosis followed by the small-group case discussion on osteoporosis prepared me adequately to understand the topic" (M = 4.56, SD = 0.63).

DISCUSSION

We developed a case-based learning activity for preclinical medical students to enhance the clinical scaffolding of basic science and medical knowledge around osteoporosis. Students performed well on session-relevant exam questions, demonstrating competency in the educational objectives. Student satisfaction was high, with most students feeling well prepared.

Active Learning to Promote Early and Effective Physician Interaction with Pharmaceutical Industry Marketing Practices

BACKGROUND

Interactions with pharmaceutical companies influence physicians' prescribing behavior. Less than half of US family medicine residency programs have educational curricula addressing their influence. However, medical students have extensive exposure to pharmaceutical industry marketing during their early years of training. We developed a successful and required active learning curriculum for medical students during their first-year of medical school.

METHODOLOGY

A philosopher bioethicist lectured to first-year medical students on the ethical issues surrounding the interactions with pharmaceutical representatives and outlined the three principles approach to clinical ethics as presented in the American Board of Internal Medicine Physician Charter (2002). The lecture also described the eight physician types offered by Fugh-Berman et al. Students watched two fictitious physician-pharmaceutical representative interactions. To promote active learning, students were provided a 3 × 3 Bingo card with each physician type. The bioethicist facilitated a discussion addressing the interactions.

RESULTS

Two hundred twenty-nine first-year medical students participated in this required intervention. Fifty-two percent of first-year medical students had already interacted with pharmaceutical representatives. The session changed students' opinions of pharmaceutical representatives and their ability to identify strategies to mitigate their influence. Students articulated ethical issues involved in the interaction, techniques used by pharmaceutical representatives, and techniques that could be used by medical students or physicians. Ninety-one percent of students believed they could independently find reliable information about a drug.

CONCLUSION

The session was effective to start the conversation regarding the ethical issues involved with the interaction between medical students/physicians and pharmaceutical representatives in the first year of medical school.

Taking CBL to the Lecture Hall: a Comparison of Outcomes Between Traditional Small Group CBL and a Novel Large Group Team-Based CBL Teaching Method

PURPOSE

Case-based learning (CBL), an important component of medical school curricula, is an effective inquiry-based teaching method associated with high levels of student and teacher satisfaction. However, because traditional CBL requires small groups, its feasibility is limited by faculty and resources. We developed and tested a novel team-based CBL (TB-CBL) method to be implemented in the lecture hall.

METHODS

All second-year students at our institution (n = 121) were randomized to either traditional small group CBL or TB-CBL during the Endocrine block and to the other modality during the Renal block. All students were exposed to both methods. Case content was identical, and sessions were run concurrently. This cross-over, non-inferiority study tested the hypothesis that no difference in knowledge acquisition, clinical reasoning, or student satisfaction would be detected between groups.

RESULTS

Based on student performance on case-relevant exam questions, no difference in knowledge acquisition was seen between groups for either block (p = 0.62 Endocrine, p = 0.38 Renal). There was also no difference in overall final exam performance between groups (p = 0.56 Endocrine, p = 0.26 Renal). Case-relevant script concordance testing revealed no difference in clinical reasoning skills between groups (p = 0.87 Endocrine, p = 0.17 Renal). Satisfaction was higher for the TB-CBL format (p = 0.005). Cost analysis revealed that each small group CBL session costs $2654, while each TB-CBL session costs approximately $221.

CONCLUSIONS

TB-CBL, a novel case-based teaching method, appears to produce similar learner outcomes and higher student satisfaction when compared with small group CBL. TB-CBL may be used to supplement case-based curricula while optimizing resource allocation.

Contraceptive Pharmacology and Risk Communication: A Case-Based Flipped Classroom Exercise

INTRODUCTION

Oral contraceptives are widely used for both contraceptive and noncontraceptive purposes. Of women ages 15-44 who have ever had sexual intercourse, 88% have used at least one hormonal contraceptive method. Health care providers caring for reproductive-age women need a strong base of knowledge in hormonal contraception. Those who provide contraceptive counseling must apply this knowledge to shared decision making, including effective quantitative communication.

METHODS

Students and faculty at Florida International University Herbert Wertheim College of Medicine created a prerecorded lecture and in-class interactive case on contraceptive pharmacology and risk communication. The 20-minute lecture focused on mechanisms of action, bioavailability, drug-drug interaction, effectiveness, and major vascular risks of combined hormonal and progestin-only contraceptives. The 55-minute in-class session integrated knowledge of risks and effectiveness of contraception with risk communication surrounding contraceptive decision making and counseling. For the 2018 academic year, 122 first-year medical students participated in the session. Students anonymously answered three questions related to the session on their end-of-course evaluation. Student learning was assessed with five multiple-choice questions on the pharmacology final exam.

RESULTS

Students rated the session very positively. They highly rated the lecture's utility and the sesssion's contribution to solidifying their basic science knowledge and understanding of its clinical applications. Class average performance on the relevant final exam questions was 88.4%.

DISCUSSION

The lecture and case discussion successfully addressed gaps in the curriculum and provided students the opportunity to integrate multiple domains of learning. Students' perception of the materials was positive, and they demonstrated adequate learning.

Culture and Expansion of Rodent and Porcine Schwann Cells for Preclinical Animal Studies

Cell-based therapies have become a major focus in preclinical research that leads to clinical application of a therapeutic product. Since 1990, scientists at the Miami Project to Cure Paralysis have generated extensive data demonstrating that Schwann cell (SC) transplantation supports spinal cord repair in animals with spinal cord injury. After preclinical efforts in SC transplantation strategies, efficient methods for procuring large, essentially pure populations of SCs from the adult peripheral nerve were developed for rodent and pig studies. This chapter describes a series of simple procedures to obtain and cryopreserve large cultures of highly purified adult nerve-derived SCs without the need for additional purification steps. This protocol permits the derivation of ≥90% pure rodent and porcine SCs within 2-4 weeks of culture.

Human Schwann cells exhibit long-term cell survival, are not tumorigenic and promote repair when transplanted into the contused spinal cord

The transplantation of rodent Schwann cells (SCs) provides anatomical and functional restitution in a variety of spinal cord injury (SCI) models, supporting the recent translation of SCs to phase 1 clinical trials for human SCI. Whereas human (Hu)SCs have been examined experimentally in a complete SCI transection paradigm, to date the reported behavior of SCs when transplanted after a clinically relevant contusive SCI has been restricted to the use of rodent SCs. Here, in a xenotransplant, contusive SCI paradigm, the survival, biodistribution, proliferation and tumorgenicity as well as host responses to HuSCs, cultured according to a protocol analogous to that developed for clinical application, were investigated. HuSCs persisted within the contused nude rat spinal cord through 6 months after transplantation (longest time examined), exhibited low cell proliferation, displayed no evidence of tumorigenicity and showed a restricted biodistribution to the lesion. Neuropathological examination of the CNS revealed no adverse effects of HuSCs. Animals exhibiting higher numbers of surviving HuSCs within the lesion showed greater volumes of preserved white matter and host rat SC and astrocyte ingress as well as axon ingrowth and myelination. These results demonstrate the safety of HuSCs when employed in a clinically relevant experimental SCI paradigm. Further, signs of a potentially positive influence of HuSC transplants on host tissue pathology were observed. These findings show that HuSCs exhibit a favorable toxicity profile for up to 6 months after transplantation into the contused rat spinal cord, an important outcome for FDA consideration of their use in human clinical trials.

Preliminary evaluation of urinary soluble Met as a biomarker for urothelial carcinoma of the bladder

BACKGROUND

Among genitourinary malignancies, bladder cancer (BCa) ranks second in both prevalence and cause of death. Biomarkers of BCa for diagnosis, prognosis and disease surveillance could potentially help prevent progression, improve survival rates and reduce health care costs. Among several oncogenic signaling pathways implicated in BCa progression is that of hepatocyte growth factor (HGF) and its cell surface receptor, Met, now targeted by 25 experimental anti-cancer agents in human clinical trials. The involvement of this pathway in several cancers is likely to preclude the use of urinary soluble Met (sMet), which has been correlated with malignancy, for initial BCa screening. However, its potential utility as an aid to disease surveillance and to identify patients likely to benefit from HGF/Met-targeted therapies provide the rationale for this preliminary retrospective study comparing sMet levels between benign conditions and primary BCa, and in BCa cases, between different disease stages.

METHODS

Normally voided urine samples were collected from patients with BCa (Total: 183; pTa: 55, pTis: 62, pT1: 24, pT2: 42) and without BCa (Total: 83) on tissue-procurement protocols at three institutions and sMet was measured and normalized to urinary creatinine. Normalized sMet values grouped by pathologic stage were compared using non-parametric tests for correlation and significant difference. ROC analyses were used to derive classification models for patients with or without BCa and patients with or without muscle-invasive BCa (MIBCa or NMIBCa).

RESULTS

Urinary sMet levels accurately distinguished patients with BCa from those without (p<0.0001, area under the curve (AUC): 0.7008) with limited sensitivity (61%) and moderate specificity (76%), and patients with MIBCa (n=42) from those with NMIBCa (n=141; p<0.0001, AUC: 0.8002) with moderate sensitivity and specificity (76% and 77%, respectively) and low false negative rate (8%).

CONCLUSIONS

Urinary sMet levels distinguish patients with BCa from those without, and patients with or without MIBCa, suggesting the potential utility of urinary sMet as a BCa biomarker for surveillance following initial treatment. Further studies are warranted to determine its potential value for prognosis in advanced disease, predicting treatment response, or identifying patients likely to benefit from Met-targeted therapies.

Urinary Met level as a novel biomarker for urothelial carcinoma of the bladder

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Background: To determine whether urinary soluble Met (sMet) can differentiate between benign conditions and bladder cancer (CaB), and in cases of bladder cancer, between different stages of transitional cell carcinoma (TCC).

Methods: Urinary samples from patients with (Total: 63, pTa: 12, pTis: 22, pT1: 13, ≥ pT2: 16) and without (Total: 27) CaB from three different institutions were prospectively collected prior to cystosopy, TURBT or cystectomy. sMet levels were determined by electrochemiluminescence immunoassay and normalized to urinary creatinine values. Normalized sMet values were compared to final pathologic stage. AUC values were obtained comparing patients with and without TCC.

Results: Urinary sMet levels accurately differentiated between patients with and without CaB (AUC: 78%, sensitivity, specificity and negative predictive value were: 68%, 78% and 95%, respectively), patients with no CaB and those with lamina propria invasion (AUC: 79%, sensitivity, specificity and negative predictive value were: 65%, 81% and 95%, respectively) and patients with no CaB and those with muscle invasive CaB (AUC: 85%, sensitivity, specificity and negative predictive value were: 75%, 83% and 97%, respectively).

Conclusions: Urinary sMet levels accurately distinguish patients with CaB from those without, and between patients with different CaB stages. These results suggest that urinary sMet may have utility as a bladder cancer marker for screening, treatment follow-up and clinical trial design.

No significant financial relationships to disclose.

Myofibril-inducing RNA (MIR) is essential for tropomyosin expression and myofibrillogenesis in axolotl hearts

The Mexican axolotl, Ambystoma mexicanum, carries the naturally-occurring recessive mutant gene 'c' that results in a failure of homozygous (c/c) embryos to form hearts that beat because of an absence of organized myofibrils. Our previous studies have shown that a noncoding RNA, Myofibril-Inducing RNA (MIR), is capable of promoting myofibrillogenesis and heart beating in the mutant (c/c) axolotls. The present study demonstrates that the MIR gene is essential for tropomyosin (TM) expression in axolotl hearts during development. Gene expression studies show that mRNA expression of various tropomyosin isoforms in untreated mutant hearts and in normal hearts knocked down with double-stranded MIR (dsMIR) are similar to untreated normal. However, at the protein level, selected tropomyosin isoforms are significantly reduced in mutant and dsMIR treated normal hearts. These results suggest that MIR is involved in controlling the translation or post-translation of various TM isoforms and subsequently of regulating cardiac contractility.

Non-antagonistic relationship between mitogenic factors and cAMP in adult Schwann cell re-differentiation

The expression of myelination-associated genes (MGs) can be induced by cyclic adenosine monophosphate (cAMP) elevation in isolated Schwann cells (SCs). To further understand the effect of known SC mitogens in the regulation of SC differentiation, we studied the response of SCs isolated from adult nerves to combined cAMP, growth factors, including neuregulin, and serum. In adult SCs, the induction of MGs by cAMP coincided with the loss of genes expressed in non-myelin-forming SCs and with a change in cell morphology from a bipolar to an expanded epithelial-like shape. Prolonged treatment with high doses of cAMP-stimulating agents, as well as low cell density, was required for the induction of SC differentiation. Stimulation with serum, neuregulin alone, or other growth factors including PDGF, IGF and FGF, increased SC proliferation but did not induce the expression of MGs or the associated morphological change. Most importantly, when these factors were administered in combination with cAMP-stimulating agents, SC proliferation was synergistically increased without reducing the differentiating activity of cAMP. Even though the initiation of DNA synthesis and the induction of differentiation were mostly incompatible events in individual cells, SCs were able to differentiate under conditions that also supported active proliferation. Overall, the results indicate that in the absence of neurons, cAMP can trigger SC re-differentiation concurrently with, but independently of, growth factor signaling.

Directed discovery of agents targeting the Met tyrosine kinase domain by virtual screening

Hepatocyte growth factor (HGF) is an important regulator of normal development and homeostasis, and dysregulated signaling through the HGF receptor, Met, contributes to tumorigenesis, tumor progression, and metastasis in numerous human malignancies. The development of selective small-molecule inhibitors of oncogenic tyrosine kinases (TK) has led to well-tolerated, targeted therapies for a growing number of cancer types. To identify selective Met TK inhibitors, we used a high-throughput virtual screen of the 13.5 million compound ChemNavigator database to find compounds most likely to bind to the Met ATP binding site and to form several critical interactions with binding site residues predicted to stabilize the kinase domain in its inactive conformation. Subsequent biological screening of 70 in silico hit structures using cell-free and intact cell assays identified three active compounds with micromolar IC(50) values. The predicted binding modes and target selectivity of these compounds are discussed and compared to other known Met TK inhibitors.

Selectivity and mechanism of action of a growth factor receptor-bound protein 2 SRC homology 2 domain binding antagonist

We have shown previously that a potent synthetic antagonist of growth factor receptor-bound protein 2 (Grb2) Src homology 2 (SH2) domain binding (1) blocks growth factor stimulated motility, invasion, and angiogenesis in cultured cell models, as well as tumor metastasis in animals. To characterize the selectivity of 1 for the SH2 domain of Grb2 over other proteins containing similar structural binding motifs, we synthesized a biotinylated derivative (3) that retained high affinity Grb2 SH2 domain binding and potent biological activity. To investigate the selectivity of 1 and 3 for Grb2, the biotinylated antagonist 3 was used to immobilize target proteins from cell extracts for subsequent identification by mass spectrometry. Non-specific binding was identified in parallel using a biotinylated analogue that lacked a single critical binding determinant. The mechanism of action of the antagonist was further characterized by immunoprecipitation, immunoblotting, and light microscopy. This approach to defining protein binding antagonist selectivity and molecular basis of action should be widely applicable in drug development.

Protein kinase A-mediated gating of neuregulin-dependent ErbB2-ErbB3 activation underlies the synergistic action of cAMP on Schwann cell proliferation

In Schwann cells (SCs), cyclic adenosine monophosphate (cAMP) enhances the action of neuregulin, the most potent known mitogen for SCs, by synergistically increasing the activation of two crucial signaling pathways: ERK and Akt. However, the underlying mechanism of cross-talk between neuregulin and cAMP signaling remains mostly undefined. Here, we report that the activation of protein kinase A (PKA), but not that of exchange protein activated by cAMP (EPAC), enhances S-phase entry of SCs by synergistically enhancing the ligand-dependent tyrosine phosphorylation/activation of the neuregulin co-receptor, ErbB2-ErbB3. The role of PKA in neuregulin-ErbB signaling was confirmed using PKA inhibitors, pathway-selective cAMP analogs, and natural ligands stimulating PKA activity in SCs, such as adenosine and epinephrine. Two basic observations defined the synergistic action of PKA as "gating" for neuregulin-ErbB signaling: 1) the activation of PKA was not sufficient to induce S-phase entry or the activation of either ErbB2 or ErbB3; and 2) the presence of neuregulin was strictly required to ignite ErbB activation and thereby ERK and Akt signaling. However, PKA directly phosphorylated ErbB2 on Thr-686, a highly conserved intracellular regulatory site that was required for the PKA-mediated synergistic enhancement of neuregulin-induced ErbB2-ErbB3 activation and proliferation in SCs. The gating action of PKA on neuregulin-induced ErbB2-ErbB3 activation has important biological significance, because it insures signal amplification into the ERK and Akt pathways without compromising either the neuregulin dependence or the high specificity of ErbB signaling pathways.

Inhibition of N-cadherin and beta-catenin function reduces axon-induced Schwann cell proliferation

N-cadherin and beta-catenin are involved in cell adhesion and cell cycle in tumor cells and neural crest. Both are expressed at key stages of Schwann cell (SC) development, but little is known about their function in the SC lineage. We studied the role of these molecules in adult rat derived SC-embryonic dorsal root ganglion cocultures by using low-Ca(2+) conditions and specific blocking antibodies to interfere with N-cadherin function and by using small interfering RNA (siRNA) to decrease beta-catenin expression in both SC-neuron cocultures and adult rat-derived SC monocultures. N-cadherin blocking conditions decreased SC-axon association and reduced axon-induced SC proliferation. In SC monocultures, beta-catenin reduction diminished the proliferative response of SCs to the mitogen beta1-heregulin, and, in SC-DRG cocultures, beta-catenin reduction inhibited axon-contact-dependent SC proliferation. Stimulation of SC cultures with beta1-heregulin increased total beta-catenin protein amount, phosphorylation of GSK-3beta and beta-catenin presence in nuclear extracts. In conclusion, our findings suggest a previously unrecognized contribution of beta-catenin and N-cadherin to axon-induced SC proliferation.

Role of myofibril-inducing RNA in cardiac TnT expression in developing Mexican axolotl

The Mexican axolotl, Ambystoma mexicanum, has been a useful animal model to study heart development and cardiac myofibrillogenesis. A naturally-occurring recessive mutant, gene "c", for cardiac non-function in the Mexican axolotl causes a failure of myofibrillogenesis due to a lack of tropomyosin expression in homozygous mutant (c/c) embryonic hearts. Myofibril-inducing RNA (MIR) rescues mutant hearts in vitro by promoting tropomyosin expression and myofibril formation thereafter. We have studied the effect of MIR on the expression of various isoforms of cardiac troponin T (cTnT), a component of the thin filament that binds with tropomyosin. Four alternatively spliced cTnT isoforms have been characterized from developing axolotl heart. The expression of various cTnT isoforms in normal, mutant, and mutant hearts corrected with MIR, is evaluated by real-time RT-PCR using isoform specific primer pairs; MIR affects the total transcription as well as the splicing of the cTnT in axolotl heart.

c-Met ectodomain shedding rate correlates with malignant potential

PURPOSE

Many proteins are proteolytically released from the cell surface by a process known as ectodomain shedding. Shedding occurs under normal physiologic conditions and can be increased in certain pathologies. Among the many receptors for which ectodomain shedding has been shown is c-Met, the hepatocyte growth factor (HGF) receptor tyrosine kinase. HGF stimulates mitogenesis, motogenesis, and morphogenesis in a variety of cellular targets during development, homeostasis, and tissue regeneration. Inappropriate HGF signaling resulting in unregulated cell proliferation, motility, and invasion occurs in several human malignancies. This can occur through paracrine signaling, autocrine loop formation, receptor mutation, gene amplification, or gene rearrangement, accompanied frequently with overexpression of ligand and/or receptor proteins. We hypothesized that c-Met overexpression in cancer might result in increased ectodomain shedding, and that its measure could be a useful biomarker of tumor progression.

EXPERIMENTAL DESIGN

We developed a sensitive electrochemiluminescent immunoassay to quantitate c-Met protein in cell lysates, culture supernatants, and biological samples.

RESULTS

A survey of cultured cell models of oncogenic transformation revealed significant direct correlations (P < 0.001, t test or ANOVA) between malignant potential and the rate of c-Met ectodomain shedding that was independent of steady-state receptor expression level. Moreover, weekly plasma and urine samples from mice harboring s.c. human tumor xenografts (n = 4 per group) displayed soluble human c-Met levels that were measurable before tumors became palpable and that correlated directly with tumor volume (R2 > 0.92, linear regression).

CONCLUSIONS

For a variety of human cancers, c-Met ectodomain shedding may provide a reliable and practical indicator of malignant potential and overall tumor burden.

Molecular and immunohistochemical analyses of cardiac troponin T during cardiac development in the Mexican axolotl,Ambystoma mexicanum

The Mexican axolotl, Ambystoma mexicanum, is an excellent animal model for studying heart development because it carries a naturally occurring recessive genetic mutation, designated gene c, for cardiac nonfunction. The double recessive mutants (c/c) fail to form organized myofibrils in the cardiac myoblasts resulting in hearts that fail to beat. Tropomyosin expression patterns have been studied in detail and show dramatically decreased expression in the hearts of homozygous mutant embryos. Because of the direct interaction between tropomyosin and troponin T (TnT), and the crucial functions of TnT in the regulation of striated muscle contraction, we have expanded our studies on this animal model to characterize the expression of the TnT gene in cardiac muscle throughout normal axolotl development as well as in mutant axolotls. In addition, we have succeeded in cloning the full-length cardiac troponin T (cTnT) cDNA from axolotl hearts. Confocal microscopy has shown a substantial, but reduced, expression of TnT protein in the mutant hearts when compared to normal during embryonic development.

The von Hippel-Lindau tumor suppressor gene product represses oncogenic beta-catenin signaling in renal carcinoma cells

Loss of von Hippel-Lindau (VHL) tumor suppressor gene function occurs in familial and most sporadic clear cell renal cell carcinoma (RCC), resulting in the aberrant expression of genes that control cell proliferation, invasion, and angiogenesis. The molecular mechanisms by which VHL loss leads to tumorigenesis are not yet fully defined. VHL loss has been shown to allow robust RCC cell motility, invasiveness, and morphogenesis in response to hepatocyte growth factor (HGF) stimulation, processes that are known to contribute to tumor invasiveness and metastatic potential. Among the most likely intracellular mediators of these HGF-driven activities is beta-catenin, a structural link between cadherens and the actin cytoskeleton, as well as a gene transactivator. We show that reconstitution of VHL expression in RCC cells repressed HGF-stimulated beta-catenin tyrosyl phosphorylation, adherens junction disruption, cytoplasmic beta-catenin accumulation, and reporter gene transactivation in RCC cells. Ectopic expression of a ubiquitination-resistant beta-catenin mutant specifically restored HGF-stimulated invasion and morphogenesis in VHL-transfected RCC cells. VHL gene silencing in non-RCC renal epithelial cells phenotypically mimicked VHL loss in RCC, and HGF-driven invasiveness was blocked by the expression of a dominant-negative mutant of Tcf. We conclude that, unlike many other cancers, where HGF pathway activation contributes to malignancy through the acquisition of autocrine signaling, receptor overexpression, or mutation, in RCC cells VHL loss enables HGF-driven oncogenic beta-catenin signaling. These findings identify beta-catenin as a potential target in biomarker and drug development for RCC.