Combination of Sulindac and Eflornithine Delays the Need for Lower Gastrointestinal Surgery in Patients With Familial Adenomatous Polyposis: Post Hoc Analysis of a Randomized Clinical Trial

BACKGROUND

Colectomy and proctocolectomy are the initial standard of care for patients with familial adenomatous polyposis. Pharmacotherapy to prevent the progression of polyposis and surgeries in the lower GI tract would be beneficial to patients with this disease.

OBJECTIVE

This analysis aimed to evaluate the impact of eflornithine-sulindac combination versus monotherapy in delaying time to disease progression in the lower GI tract of patients with familial adenomatous polyposis.

DESIGN

This is a post hoc analysis of a randomized phase 3 trial.

SETTING

This study was conducted in 21 hospitals in 7 countries treating patients with familial adenomatous polyposis.

PATIENTS

Adults with familial adenomatous polyposis were randomly assigned 1:1:1 into 3 arms.

INTERVENTIONS

Patients received either eflornithine (750 mg), sulindac (150 mg), or both once daily for up to 48 months.

MAIN OUTCOME MEASURES

Efficacy was evaluated as the time from randomization to predefined primary disease progression end points.

RESULTS

A total of 158 patients were included in the study. Disease progression was observed in 2 of 54 (3.7%), 9 of 53 (17.0%), and 10 of 51 (19.6%) patients with at least partial lower GI tract in the combination, sulindac, and eflornithine arms, corresponding to risk reductions of 80% (p = 0.02) and 83% (p = 0.01) between combination and sulindac or eflornithine. When endoscopic excision of adenomas ≥10 mm in size was censored, the need for major surgery was observed in 0 of 54, 7 of 53 (13.2%), and 8 of 51 (15.7%) patients in the combination, sulindac, and eflornithine arms, corresponding to risk reductions approaching 100% between combination and sulindac (p = 0.005) or combination and eflornithine (p = 0.003).

LIMITATIONS

This was a post hoc analysis, the sample size was small, and there were fewer than expected events.

CONCLUSIONS

Eflornithine-sulindac combination therapy was superior to either drug alone in delaying or preventing the need for lower GI tract surgery in patients with familial adenomatous polyposis. See Video Abstract at http://links.lww.com/DCR/B658.

REGISTRATION

ClinicalTrials.gov, NCT01483144; EU Clinical Trials Register, EudraCT 2012-000427-41.

LA COMBINACIN DE SULINDAC Y EFLORNITINA RETRASA LA NECESIDAD DE CIRUGA DEL TUBO DIGESTIVO BAJO EN PACIENTES CON PAF ANLISIS POSTHOC DE UN ENSAYO CLNICO ALEATORIZADO

ANTECEDENTES:La colectomía y la proctocolectomía son el estándar inicial de atención para los pacientes con poliposis adenomatosa familiar. La farmacoterapia para prevenir la progresión de la poliposis y las cirugías en el tracto gastrointestinal inferior sería beneficiosa para los pacientes con esta enfermedad.OBJETIVO:Este análisis tuvo como objetivo evaluar el impacto de la combinación de eflornitina-sulindac versus la monoterapia en el retraso del tiempo hasta la progresión de la enfermedad en el tracto gastrointestinal inferior de pacientes con poliposis adenomatosa familiar.DISEÑO:Este es un análisis posthoc de un ensayo de fase 3 aleatorizado.ENTORNO CLINICO:Veintiún hospitales en 7 países que tratan a pacientes con poliposis adenomatosa familiar.PACIENTES:Adultos con poliposis adenomatosa familiar fueron aleatorizados 1: 1: 1 en 3 brazos.INTERVENCIONES:Los pacientes recibieron eflornitina (750 mg), sulindac (150 mg) o ambos una vez al día durante un máximo de 48 meses.PRINCIPALES MEDIDAS DE VALORACION:La eficacia se evaluó como el tiempo desde la aleatorización hasta los criterios de valoración primarios predefinidos de progresión de la enfermedad.RESULTADOS:Los resultados se informan para la población de estudio excluyendo a los pacientes que se habían sometido a ileostomías permanentes (n = 158). Se observó progresión de la enfermedad en 2/54 (3,7%), 9/53 (17,0%) y 10/51 (19,6%) pacientes con al menos tracto gastrointestinal inferior parcial en los brazos de combinación, sulindac y eflornitina, respectivamente, correspondientes al riesgo de reducciones del 80% (p = 0,02) y del 83% (p = 0,01) entre la combinación y el sulindaco o la eflornitina, respectivamente. Cuando se censuró la escisión endoscópica de adenomas ≥10 mm de tamaño, se observó la necesidad de cirugía mayor en 0/54, 7/53 (13,2%) y 8/51 (15,7%) pacientes en la combinación, sulindac y eflornitina, respectivamente, correspondientes a reducciones de riesgo cercanas al 100% entre combinación y sulindac (p = 0,005) o combinación y eflornitina (p = 0,003).LIMITACIONES:Este fue un análisis posthoc, el tamaño de la muestra fue pequeño y hubo menos eventos de los esperados.CONCLUSIONES:La terapia de combinación de eflornitina-sulindac fue superior a cualquier fármaco solo para retrasar o prevenir la necesidad de cirugía del tracto gastrointestinal inferior en pacientes con poliposis adenomatosa familiar. Consulte Video Resumen en http://links.lww.com/DCR/B658.

A small-molecule activator of the unfolded protein response eradicates human breast tumors in mice

Metastatic estrogen receptor α (ERα)-positive breast cancer is presently incurable. Seeking to target these drug-resistant cancers, we report the discovery of a compound, called ErSO, that activates the anticipatory unfolded protein response (a-UPR) and induces rapid and selective necrosis of ERα-positive breast cancer cell lines in vitro. We then tested ErSO in vivo in several preclinical orthotopic and metastasis mouse models carrying different xenografts of human breast cancer lines or patient-derived breast tumors. In multiple orthotopic models, ErSO treatment given either orally or intraperitoneally for 14 to 21 days induced tumor regression without recurrence. In a cell line tail vein metastasis model, ErSO was also effective at inducing regression of most lung, bone, and liver metastases. ErSO treatment induced almost complete regression of brain metastases in mice carrying intracranial human breast cancer cell line xenografts. Tumors that did not undergo complete regression and regrew remained sensitive to retreatment with ErSO. ErSO was well tolerated in mice, rats, and dogs at doses above those needed for therapeutic responses and had little or no effect on normal ERα-expressing murine tissues. ErSO mediated its anticancer effects through activation of the a-UPR, suggesting that activation of a tumor protective pathway could induce tumor regression.

Abstract 1217: Development of a spontaneous in vivo cachexia model using the Champions TumorGraft™ platform

Cachexia is present in the majority of patients with advanced cancer progression and is not reversible through nutritional supplementation, leading to loss of skeletal muscle and adipose tissue. There are a lack of quality pre-clinical models for cachexia research. Previously, Champions Oncology reported a mouse cachexia model derived from a primary human renal cell carcinoma tumor implanted in immunocompromised mice. This model, CTG-0804, was developed using the innovative Champions TumorGraft™ platform, which preserves the biological properties of the original human tumor. The Champions TumorGraft platform demonstrated dramatic weight loss in these mice as the tumor grew. Plasma from these mice also showed elevated levels of human IL-6. We have now further characterized this TumorGraft model by evaluating standard of care (SOC) agents for renal cell carcinoma and anti-IL-6 compounds to determine the mechanism of cachexia. The SOC evaluation revealed that sorafenib, sunitinib, temsirolimus and bevacizumab as single agents provided a survival advantage by inhibiting tumor growth and preventing weight loss in these mice. Blockade of human IL-6 with tocilizumab or ALD518 did not inhibit tumor growth and weight loss still occurred, demonstrating the possibility of other pathways involved in the cachexia mechanism. In addition, the SOC data for sunitinib showed significant tumor growth inhibition, but no regression at the study end point. This correlated with the clinical profile, where sunitinib could not prevent metastasis and the patient eventually progressed. The TumorGraft model was molecularly characterized and mutation analysis revealed a KIT V530I mutation. This mutation has been reported in extra-abdominal aggressive fibromatosis (desmoid tumor) and acute myeloid leukemia patients that have responded to c-kit targeting therapies, such as imatanib and dasatinib. Further characterization of this TumorGraft is ongoing to include additional bioinformatics using gene expression and mutation pathway analyses. In summary, we have continued development of this cachexia model using the Champions TumorGraft platform, along with molecular evaluation, to produce a robust and well-characterized approach for cachexia investigation which can also be applied to other areas of drug development and cancer research.

Citation Format: Nathan Anderson, Tin Khor, Andrew Feldhaus, Andreya Gatling, Katie Olson, John Latham, David Sidransky, Elizabeth M. Bruckheimer. Development of a spontaneous in vivo cachexia model using the Champions TumorGraft™ platform. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1217. doi:10.1158/1538-7445.AM2014-1217

Abstract 2793: Development of an androgen-dependent prostate Champions TumorGraft™ cancer model

Prostate cancer (PCa)is the second most frequently diagnosed cancer and the sixth leading cause of cancer death in males, with the highest incidence rates recorded in developed countries such as those in North America (Jemal et al., 2011). While the five year-survival rate for PCa patients with localized disease is 100%, it is only 30.6% once the cancer metastasizes (Vishnu et al., 2010). One of the biggest challenges for finding a better treatment for metastatic PCa is the lack of predictable and accurate preclinical models that closely recapitulate different stages of the pathogenesis of human PCa. Champions Oncology focuses on the development of Champions TumorGraft™ models derived from the direct implantation of patient tumors into immunocompromised mice. Compared to traditional cell line-based xenograft models, the patient-derived TumorGraft models maintain stable gene-expression patterns and mutational status and correlate to clinical predictability. To overcome the challenge for PCa, Champions Oncology has utilized its TumorGraft technology to establish and characterize a new androgen-dependent prostate cancer TumorGraft model, CTG-0488. This involved the implantation of a primary human prostate tumor in immunocompromised mice in a manner that preserves the biological properties of the original human tumor. In this preliminary work, the characteristics of Champion TumorGraft™ model CTG-0488 are showcased, including tumor histology, mutational status, and chemosensitivity profiles to several standard of care compounds. Overall the development of an androgen-dependent prostate cancer Champions TumorGraft™ model will significantly aid in the development of oncology compounds focused on androgen-dependent prostate cancer.

Citation Format: Tin Oo Khor, Keren Paz, Dhanrajan Tiruchinapalli, David Sidransky, Elizabeth M. Bruckheimer. Development of an androgen-dependent prostate Champions TumorGraft™ cancer model. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2793. doi:10.1158/1538-7445.AM2013-2793

Abstract 2781: Champions TumorGraft™ models possess PIK3CA mutations - A great tool to explore the PI3K/AKT pathway

Phosphatidylinositol 3-kinase (PI3K) is an important intracellular signal transducer that is involved in many cellular functions such as cell growth, proliferation, and differentiation. PI3K is a heterodimeric molecule composed of a regulatory and a catalytic subunit. PIK3CA, which encodes the p110α catalytic subunit, is often mutated in a range of human cancers, such as colorectal and non-small-cell lung cancers. Increasing our understanding of the biological implications of these mutations and the role of PI3K pathway in cancer proliferation or survival may lead to potential new therapeutic opportunities targeting PI3K signaling.

Champions Oncology focuses on the development of TumorGraft models derived from the direct implantation of patient tumors into immunocompromised mice. Compared to traditional cell line-based xenograft models, the patient derived Champions TumorGraft™ models maintain stable gene-expression patterns and mutational status and correlate to clinical predictability. Through extensively characterization, Champions has identified 19 TumorGraft models with PIK3CA mutations. Out of these 19 models, there are 11 colorectal cancers, 3 non-small cell lung cancers, 3 pancreatic cancers, 1 gastric cancer and 1 melanoma. Genomics analyses using the Ampliseq platform identified the majority of PIK3CA mutations in exon 9 and 20. Mutations in these regions of PIK3CA are known to confer resistance to some anti-cancer agents, such as HER2 antibodies. Additionally, it has been reported that PIK3CA mutations frequently coexist with RAS and BRAF mutations in patients with advanced cancers. Upon further analysis, we identified the same pattern in Champions TumorGraft models where∼70% (13 out of 19) of the PIK3CA mutant models possess either concurrent RAS or BRAF mutations. Notably, PI3K activates the downstream kinase AKT which ultimately triggers the mTOR pathway. Mutations in cancer often result in constitutive activation of this pathway. Given the role of the PI3K/AKT signaling in cancer and the presence of these specific mutations in the Champions TumorGraft bank, utilization of Champions’ TumorGraft models in oncology drug development allows for greater insight into new therapeutic opportunities targeting the inhibition of PI3K/AKT signaling and offers new promise for patients with these activated pathways.

Citation Format: Tin Oo Khor, Dhanrajan Tiruchinapalli, Jay Friedman, Nathan Anderson, David Sidransky, Elizabeth M. Bruckheimer. Champions TumorGraft™ models possess PIK3CA mutations - A great tool to explore the PI3K/AKT pathway. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2781. doi:10.1158/1538-7445.AM2013-2781

Abstract 2798: Champions TumorGraft™ models represent oncology clinical trial populations

One of the challenges in oncology drug development is the inability of traditional in vivo models to predict clinical responses. Champions Oncology overcomes this challenge through the use of its innovative Champions TumorGraft™ platform, where primary human tumors are implanted into immunocompromised mice in a manner that preserves the biological properties of the original human tumor. The current study evaluated the molecular and demographic characteristics of the Champions TumorGraft™ bank to demonstrate that these models closely resemble cancer patients that pharmaceutical companies encounter in clinical trials during the development of innovative and targeted oncology compounds. In particular, the relative frequency of ethnicity, age, and geographic location in the Champions TumorGraft™ bank closely aligns with patients enrolled in oncology clinical trials. For instance, greater than half of the models in Champions TumorGraft bank are derived from patients with advanced disease, who failed several previous lines of therapy. This is extremely important for accurate translational research, as most patients enrolling in critical mid-stage oncology clinical trials often have advanced disease and have failed multiple lines of therapy. Additionally, in recent years, clinical trials have progressed to designs where there are specific enrichments in patient populations/sub-populations based on the incorporation of companion diagnostics. Molecular evaluation of the Champions TumorGraft™ bank identifies models that possess genomic signatures or pathway expressions which can be used to identify and validate potential enrichment strategies. For example, 40% of Champions’ NSCLC models possess p53 mutations and 36% of all NSCLC clinical cases also possess p53 mutations according to the COSMIC database. Additionally, 50% of Champions colorectal TumorGraft models possess K-ras mutations, whereas 36% the clinical colorectal cancer population possesses this mutation. These cases, as well as other mutations observed across several tumor types, demonstrate that the TumorGraft mutation prevalence is representative of the prevalence in cancer patients. Together, these results demonstrate that Champions TumorGraft™ models represent a unique preclinical in vivo platform that correlate to oncology clinical trial populations. Overall, these results suggest that Champions TumorGraft™ models are capable of predicting the clinical effectiveness of drug candidates and can accelerate and enhance oncology drug development.

Citation Format: Tin Oo Khor, Jay Friedman, Dhanrajan Tiruchinapalli, Nathan Anderson, David Sidransky, Elizabeth M. Bruckheimer. Champions TumorGraft™ models represent oncology clinical trial populations. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2798. doi:10.1158/1538-7445.AM2013-2798

Abstract 2792: Characterization of spontaneous in vivo cachexia models in Champions TumorGraft™ models

Cachexia, defined as a loss of adipose tissue and skeletal muscle mass not reversible by nutritional support, is present in the majority of patients with advanced cancer progression. This reduces the patient's quality of life and impacts their ability to function normally and undergo treatments. Reversing cachexia has been problematic due to a lack of quality pre-clinical models. Traditional xenograft models using cell lines are limited due to their inability to accurately replicate the whole body response to cancer. Champions Oncology overcomes this challenge through the use of its innovative Champions TumorGraft™ platform, where primary human tumors are implanted into immunocompromised mice in a manner that preserves the biological properties of the original human tumor. Champions has identified a panel of three TumorGraft models which spontaneously induce cachexia when implanted subcutaneously into nude mice: 1) CTG-0282, a pancreatic cancer model, 2) CTG-0765, a NSCLC model, and 3) CTG-0804, a renal cell carcinoma model. All three models have shown a greater than 90% cachexia rate, as demonstrated by lost body weight, over multiple passages. In addition, loss of body weight correlates with an increase in tumor volume size. Mice that have little or no tumor growth show no loss of body weight. Past studies have indicated a function for pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin 1 (IL-1), interleukin 6 (IL-6) and interferon gamma (IFNγ), in the cachexia process. Champions is currently investigating the roles of these possible tumor-mediated factors in the aforementioned models. Principle among these factors is IL-6, which has been shown to be required in the regulation of cachexia in tumor-bearing mice and is correlated with weight loss and survival in patients. Preliminary results from our studies suggest a correlation between IL-6 levels and spontaneous cachexia in Champions TumorGraft models. In summary, we demonstrate that the Champions TumorGraft platform preserves the biological properties of the original human tumor, including spontaneous cachexia behavior in these models, and is therefore ideal for oncology drug development programs focused on the inhibition of cachexia.

Citation Format: Nathan Anderson, Tin Oo Khor, Andrew Feldhaus, Katie Olson, John Latham, David Sidransky, Elizabeth M. Bruckheimer. Characterization of spontaneous in vivo cachexia models in Champions TumorGraft™ models. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2792. doi:10.1158/1538-7445.AM2013-2792

Abstract 1367: Characterization of spontaneous metastases in Champions TumorGraft™ models

Oncology drug development is challenged by an absence of model systems that accurately mimic the full metastatic processes during disease progression. Methods for establishing metastases generally involve orthotopic implantation or intravenous delivery of cell line-based xenografts. These cell line-based models can capture the seeding phase of the metastatic process but do not address the processes involved in remodeling of the extracellular matrix to allow for invasion into nearby tissues or dissemination to distance sites throughout the body via the lymphatic or the circulatory system. Extensive characterization of Champions TumorGraft™ models demonstrates that spontaneous metastasis in our platform may not be a rare event as it has been verified in 8 different models and preliminary data indicates multiple additional occurrences. Further, the capacity for spontaneous metastasis is not indication specific as it has been observed in Champions TumorGrafts derived from patients with multiple cancer types (e.g. ovarian, breast, H&N, and lung). The development and incidence rate of TumorGraft metastasis seems to correlate with the aggressiveness of disease and occurrence of metastases in the patient. For example, 83% of mice implanted with Champions TumorGraft breast cancer model CTG-0033 develop liver and/or spleen metastases. This Champions TumorGraft was derived from a patient with aggressive disease that failed to respond to first and second line treatments, and developed metastases in multiple organs including the liver. In this report, growth rates, metastases formation and molecular characterization in primary subcutaneous Champions TumorGraft models were compared with their corresponding metastatic lesions to identify changes that may correlate with the formation of metastases. Overall, this study further demonstrates that Champions Oncology TumorGraft platform preserves the biological properties of the original human tumor including spontaneous metastatic behavior and is therefore ideal for oncology drug development programs focused on the inhibition of metastases.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1367. doi:1538-7445.AM2012-1367

Abstract B18: Champions Tumorgraft™ models demonstrate spontaneous metastases

One of the challenges in oncology drug development is the lack of in vivo models that demonstrate the spontaneous metastatic process. Standard subcutaneous implantation of cell-line based xenografts models seldom results in the generation of spontaneous metastatic lesions. In general, experimental metastatic models are utilized which requires the intravenous injection of cells or orthotopic implantation of tumors cells to replicate metastases. These methods fail to capture the full process of metastases and only capture seeding in the distant location. Champions Oncology utilizes its innovative Champions Tumorgraft™ platform where primary human tumors are implanted into immunocompromised mice in a manner that preserves the biological properties of the original human tumor. As part of its extensive characterization, Champions has recently observed an increasing number of Champions Tumorgraft™ models demonstrating spontaneous metastatic lesions following subcutaneous (s.c.) implantation. The tumor types demonstrating spontaneous metastasis include breast, melanoma, colorectal, esophageal adenocarcinoma, and head and neck squamous cell carcinoma. Two Champions Tumorgraft models highlighted in this report are CTG-0033, a breast cancer model, and CTG-0213, a melanoma model. These Champions Tumorgraft models demonstrate frequent metastases to the liver and spleen following s.c. implantation. For model CTG-0033, metastases were seen in greater than 75% of the animals following implantation. The metastatic behavior of this Tumorgraft model also parallels the clinical disease progression. For instance, CTG-0033 was derived from a breast cancer patient who, following the development of the Tumorgraft model, developed extensive metastases. Given that treatment failures clinically are often due to recurrence of the tumor at metastatic locations, there is significant need for in vivo models that replicate the spontaneous metastatic process. Overall, numerous Champions Tumorgraft models implanted s.c. exhibit spontaneous metastatic behavior and are therefore ideal models for oncology drug development focused on inhibition of metastases.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B18.

Abstract A25: Establishment and characterization of primary human Biomerk Tumorgraft™ Models: Application to oncology drug development

One of the key challenges facing oncology drug development is the high attrition rates of compounds that enter the drug development pipeline, where very few achieve successful approval and marketing. Champions Biotechnology, in an effort to enhance the value of preclinical compounds and accelerate oncology drug development, has developed a novel preclinical platform derived from Biomerk Tumorgraft™ models; an innovative approach that utilizes the implantation of primary human tumors in immune-deficient mice in a manner that preserves the biological properties of the original human tumor. Biomerk Tumorgrafts™ differ from traditional xenograft models in that they are not passaged in tissue culture, and are instead exclusively passaged in vivo. Additionally, the Biomerk Tumorgraft™ models: (a) maintain the fundamental genotypic features of the original cancer, (b) represent the genetic heterogeneity of the cancer, and (c) do not change over several passages. Champions has established a bank of over 200 Tumorgraft models encompassing all major solid tumor types, all of which have been extensively characterized. Here we describe a panel of NSCLC lung, colon, and pancreatic tumorgraft models including gene expression profiling, mutational analyses and responses to standard of care agents. Of the NSCLC lung models, 6/8 demonstrated resistance to Erlotinib with 2/8 demonstrating an intermediate response, 2/6 also possessed a mutant K-ras or a mutant EGFR. Similarly, 3/6 K-ras mutant colon Tumorgraft models demonstrated sensitivity to irinotecan. In the case of the pancreatic models, 7/8 showed resistance to Erlotinib with the remaining model showing only a modest response. Through Champions' Personalized Oncology Services, we have also shown a high correlation between the Tumorgraft response and the clinical response. Together, these results demonstrate that each model differs with respect to its genetic composition and response to standard agents, and thus represents the efficacy of a compound on an individual patient. Given the diversity of models, the maintenance of the genomic and phenotypic characteristics of the original patient tumor, and the correlation between Tumorgraft and clinical responses, Champions Biomerk Tumorgraft™ models represent a novel preclinical in vivo platform capable of optimizing drug regimens for cancer patients and predicting the clinical effectiveness of preclinical drug candidates. Overall, the application of Biomerk Tumorgraft™ models has the potential to accelerate and enhance oncology drug development.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A25.

TGF-beta signaling and androgen receptor status determine apoptotic cross-talk in human prostate cancer cells

BACKGROUND

A signaling interaction between transforming growth factor-beta (TGF-beta) and androgens promotes apoptosis in human prostate cancer cells LNCaP-TbetaRII (androgen-sensitive and TGF-beta responsive). This study investigated the contribution of androgen receptor (AR) in the combined effect of TGF-beta and dihydrotestosterone (DHT), on regulation of apoptosis and AR- and TGF-beta mediated transcriptional activity in human prostate cancer cells.

METHODS

Transcriptional activation in response to TGF-beta (5 ng/ml) and DHT (1 nM) was evaluated using transient transfections and luciferase assays in human prostate cancer cells, LNCaP-TbetaRII and PC-3, overexpressing the wild type AR. The apoptotic response to DHT/TGFbeta treatment was correlated with AR cellular distribution and the AR interaction with TGF-beta intracellular effector Smad4.

RESULTS

The results revealed that TGF-beta signaling induced AR-mediated transcriptional activation in two androgen-responsive promoters [probasin and prostate specific antigen (PSA)]. TGF-beta1 induced transcriptional activity enhanced by DHT in both cell lines (LNCaP-TbetaRII and PC-3-AR) via AR-Smad4 interaction. This interaction however does not exclusively drive TGF-beta mediated apoptosis as DHT failed to enhance such an effect in PC-3 AR (wt) cells.

CONCLUSIONS

These results demonstrate that the AR status determines the sensitivity of prostate cancer cells to the apoptotic effects of TGF-beta1, thus providing a new insight into the mechanism via which TGF-beta cross-sections the AR axis toward the functional convergence of the two pathways in the development of androgen-independent prostate cancer. This study is potentially significant in defining the contribution of AR status to the emergence of androgen-independent prostate tumors.

Long-term suppression of experimental arthritis following intramuscular administration of a pseudotyped AAV2/1-TNFR:Fc Vector

We previously reported that administration of an adeno-associated virus 2 (AAV2) vector encoding a rat tumor necrosis factor (TNF) receptor-immunoglobulin Fc (TNFR:Fc) fusion gene to rats with streptococcal cell wall-induced arthritis resulted in suppression of joint inflammation and cartilage and bone destruction, as well as expression of joint proinflammatory cytokines. In this study, we used an alternate rat model of arthritis to compare the serum levels and duration of TNFR:Fc protein expression following intramuscular administration of pseudotyped AAV-TNFR:Fc vectors based on serotypes 1, 2, and 5. All three pseudotyped AAV-TNFR:Fc vectors led to sustained expression of serum TNFR:Fc protein for at least one year. Serum TNFR:Fc protein levels in rats administered intramuscularly with AAV2/1-TNFR:Fc vector were up to 100- and 10-fold higher than in rats administered the AAV2-TNFR:Fc or AAV2/5-TNFR:Fc vectors, respectively. A single intramuscular administration of AAV2/1-TNFR:Fc vector at vector doses ranging from 10(10) to 10(12) DNase-resistant particles (DRP) per animal, resulted in complete and long-term suppression of recurrent joint inflammation for at least 150 days. Our results establish a proof of concept for administration of an AAV2/1-TNFR:Fc vector to the muscle to achieve long-term, sustained and therapeutically relevant levels of TNFR:Fc protein to treat chronic systemic inflammatory joint diseases.

Secretion of a TNFR:Fc fusion protein following pulmonary administration of pseudotyped adeno-associated virus vectors

This study evaluated and compared delivery of the tumor necrosis factor alpha receptor (TNFR)-immunoglobulin G1 (IgG1) Fc fusion (TNFR:Fc) gene to the lung by single and repeat administrations of multiple pseudotyped adeno-associated virus (AAV) vectors as a means for achieving systemic distribution of the soluble TNFR:Fc protein. A single endotracheal administration of AAV[2/5]cytomegalovirus (CMV)-TNFR:Fc vector (containing the AAV2 inverted terminal repeats and AAV5 capsid) to the rat lung resulted in long-term, high levels of serum TNFR:Fc protein that gradually declined over a period of 8 months. Endotracheal delivery of AAV[2/1]CMV-TNFR:Fc resulted in serum TNFR:Fc protein levels that were detectable for at least 4 months but were 10-fold lower than that of the AAV[2/5] vector. In contrast, secretion of the TNFR:Fc protein following pulmonary delivery of AAV[2/2]CMV-TNFR:Fc vector was very inefficient, and the protein was detected in the blood only when an airway epithelial cell-specific promoter, CC10, was substituted for the CMV enhancer/promoter to control transgene expression. In the context of AAV[2/5], the CC10 promoter was as efficient as CMV enhancer/promoter in generating similar levels of systemic TNFR:Fc protein, suggesting that this protein is secreted primarily from the airway epithelium. In mice, comparable long-term secretion of TNFR:Fc protein was demonstrated after AAV[2/2] and AAV[2/5] delivery, although the kinetics of transduction appeared to be different. All pseudotyped AAV vectors elicited serum anti-AAV capsid-neutralizing antibody responses, but these did not prevent lung transduction and efficient secretion of TNFR:Fc protein to the circulation following readministration with AAV[2/5]. These results highlight the potential utility of AAV vectors containing serotype 5 capsid to deliver and redeliver genes of secreted proteins to the lung to achieve long-term systemic protein expression.

Regulation of Bcl-2 expression by dihydrotestosterone in hormone sensitive LNCaP-FGC prostate cancer cells

PURPOSE

Up-regulation of the anti-apoptotic bcl-2 proto-oncogene is associated with androgen independent prostate cancer progression. This observation suggests that the expression of bcl-2 may be negatively regulated by androgens in prostate cancer cells.

MATERIALS AND METHODS

The expression of the proto-oncogene bcl-2 was assessed in the hormone sensitive prostate cancer cell line LNCaP-FGC in the presence and absence of a physiological concentration of 1 nM. dihydrotestosterone (DHT). Sequence analysis of the bcl-2 promoter regions demonstrated the presence of 2 potential androgen response elements. Transient transfections of luciferase reporter constructs containing these potential androgen response elements into LNCaP-FGC cells in the presence and absence of DHT were performed. Steady-state transcripts of bcl-2 were assessed using RNase protection assays.

RESULTS

Cells cultured in charcoal stripped serum in the presence of DHT resulted in down-regulation of bcl-2 protein. Down-regulation of bcl-2 protein and mRNA by DHT was inhibited by coincubation with the antiandrogen bicalutamide, an agent that competitively inhibits binding of DHT to androgen receptor. Luciferase reporter constructs containing candidate androgen response elements were transrepressed in the presence of DHT. Bcl-2 mRNA was also down-regulated by DHT and this down-regulation could not be abolished by cycloheximide.

CONCLUSIONS

Together these results suggest that the suppression of bcl-2 expression by DHT in hormone sensitive LNCaP-FGC prostate cancer cells occurs directly. In addition, these results provide a possible mechanistic basis for the up-regulation (derepression) of bcl-2 observed in hormone independent prostate cancers.

Systemic gene therapy in human xenograft tumor models by liposomal delivery of the E1A gene

The adenovirus type 5 E1A protein has been demonstrated to elicit antitumor effects through the induction of apoptosis, inhibition of cell cycle progression, induction of differentiated epithelial phenotypes, repression of oncogene expression and function, and sensitization to chemotherapeutic agents and radiation. These unique properties have led to use of the E1A gene in adenoviral and lipid-based gene therapy systems, and it has demonstrated antitumor effects in tumor xenograft model systems. However, the delivery systems used in those studies are best suited for local or intratumoral delivery rather than systemic delivery. Because the effective treatment of many primary tumors as well as metastatic disease requires systemic delivery systems, a novel gene delivery system composed of liposome/protamine/DNA (LPD) was investigated for systemic delivery of the E1A gene. Athymic nude mice bearing human breast (MDA-MB-361) or head and neck (WSUHN-31) tumor xenografts were treated i.v. with LPD-E1A, and the expression of E1A protein and effects on tumor growth were assessed. In the MDA-MB-361 breast model, expression of E1A protein was detected in the tumors after LPD-E1A treatment, which was associated with down-regulation of HER-2/neu protein expression and the presence of apoptotic cells. Tumor volume was also smaller in mice treated with LPD-E1A than in controls in both of the xenograft models. Lastly, LPD-E1A in combination with paclitaxel was more effective than LPD-E1A or paclitaxel alone in the MDA-MB-361 model. Additional preclinical and clinical development of LPD-E1A is warranted for the treatment of advanced or metastatic cancer.

Bcl-2 antagonizes the combined apoptotic effect of transforming growth factor-beta and dihydrotestosterone in prostate cancer cells

BACKGROUND

We previously demonstrated that dihydrotestosterone (DHT) enhances transforming growth factor-beta (TGF-beta) -induced apoptosis in human prostate cancer cells (Endocrinology 2001;142:2419-2426).

METHODS

In this study, the ability of the apoptosis suppressor bcl-2 to directly antagonize the combined apoptotic effect of TGF-beta and DHT in the androgen-sensitive LNCaP TbetaRII prostate cancer cells was examined. The previously cloned TGF-RbetaII receptor LNCaP cells, responsive to both TGF-beta and androgens, were engineered to overexpress the bcl-2 oncoprotein and the profile of apoptosis induction was analyzed in response to TGF-beta alone (5.0 ng/ml) or in combination with DHT (1 nM).

RESULTS

Biological characterization of cloned LNCaP TbetaRII hygromycin/bcl-2 transfectants demonstrated that bcl-2 overexpression resulted in a significant inhibition of the combined TGF-beta and DHT apoptotic effect in prostate cancer cells (P < 0.01). Furthermore, molecular analysis indicated that this antagonistic effect of bcl-2 on apoptosis was due to partial suppression of TGF-beta and DHT-mediated induction of caspase-1 expression and activation in LNCaP TbetaRII-hygro/bcl-2 transfectants. These results support a potential bcl-2 interference with the TGF-beta and androgen apoptotic signaling in prostate cancer cells by means of an antagonistic effect on caspase-1 activation.

CONCLUSION

This evidence may have mechanistic significance in understanding the contribution of bcl-2 overexpression in the development of androgen-independent prostate cancer by means of conferring resistance to TGF-beta-mediated apoptosis.

Dihydrotestosterone enhances transforming growth factor-beta-induced apoptosis in hormone-sensitive prostate cancer cells

In this study, the potential interactions between dihydrotestosterone (DHT), a survival factor, and transforming growth factor-beta (TGF-beta), an apoptotic inducer, were examined in a derivative of the hormone-sensitive prostate cancer cell line LNCAP: The LNCaP TGF-beta receptor II cells, engineered to express TGF-beta receptor II, are sensitive to both DHT and TGF-beta. Surprisingly, when the LNCaP TGF-beta receptor II cells were treated with TGF-beta in the presence of physiological levels of DHT, both cell cycle arrest and apoptosis induction were significantly enhanced over TGF-beta alone. This effect temporally correlated with an increased expression of the cell cycle regulator p21 as well as the apoptotic executioner, procaspase-1, and a parallel down-regulation of the antiapoptotic protein, bcl-2. Expression of bax and caspase-3 proteins remained unchanged following treatment. Furthermore, apoptosis induction was suppressed by the caspase-1 inhibitor, z-YVAD, but not the caspase-3 inhibitor, z-DQMD, thus demonstrating the functional significance of increased procaspase-1 expression in TGF-beta-mediated apoptosis in prostate cancer cells. These results indicate that TGF-beta-mediated apoptosis can actually be enhanced by androgens through specific mechanisms involving cell cycle and apoptosis regulators and provide initial evidence on the ability of physiological levels of androgens to stimulate the intrinsic apoptotic potential of prostate cancer cells. Therefore, this study provides a molecular basis for the priming of prostate cancer cells for maximal apoptosis induction, during hormone- ablation therapy.

Molecular determinants of cell death induction following adenovirus-mediated gene transfer of wild-type p53 in prostate cancer cells

Adenoviral vectors expressing wild-type p53 (Ad-p53) induce apoptosis in different types of cancer cells. The therapeutic utility of Ad-p53 is now being evaluated in prostate-cancer patients. Bcl-2 is frequently expressed by prostate-cancer cells and has previously been shown to inhibit p53-mediated cell death following genotoxic stress. We studied the impact of bcl-2 on Ad-p53-induced cell death in human prostate-cancer cells. Human prostate-cancer cell lines LNCaP (p53 wt) and PC3 (p53 mut) were stably transfected with bcl-2. After p53 transduction, cell viability, apoptosis induction and modulation of specific apoptosis-regulatory proteins were assessed. LNCaP vector control and bcl-2-expressing cells underwent similar decreases in viability associated with apoptosis induction following Ad-p53 infection. Increased bcl-2 expression provided significant protection to PC3 cells transduced with Ad-p53. These findings are correlated with modulations in bax, bcl-2, bcl-x(L) and p21 protein levels. These data suggest that Ad-p53 may be useful in the treatment of some prostate cancers.

Bcl-2 accelerates multistep prostate carcinogenesis in vivo

The impact of bcl-2 proto-oncogene expression on the pathogenesis and progression of prostate cancer was examined in a transgenic mouse model. Probasin-bcl-2 transgenic mice were crossed with TRAMP (TRansgenic Adenocarcinoma Mouse Prostate) mice that express the SV40 early genes (T/t antigens) under probasin control. Prostate size, cell proliferation, apoptosis, and the incidence and latency of tumor formation were evaluated. The double transgenic, probasin-bcl-2 X TRAMP F1 (BxT) mice exhibited an increase in the wet weight of the prostate. This was associated with an increase in proliferation, attributable to T/t antigens, and a decrease in apoptosis attributable to bcl-2. The latency to tumor formation was also decreased in the BxT mice compared to the TRAMP mice. The incidence of metastases was identical in both the TRAMP and BxT mice. Lastly, the incidence of hormone-independent prostate cancer was reduced in the BxT mice compared to the TRAMP mice. Together, these results demonstrate that bcl-2 can facilitate multistep prostate carcinogenesis in vivo.

Cell proliferation and apoptosis in prostate cancer: significance in disease progression and therapy

Recent biochemical and genetic studies have substantially increased our understanding of death signal transduction pathways, making it clear however, that apoptosis is not a single-lane, one-way street. Rather, multiple parallel pathways have been identified. For instance, analysis of bcl-2, bax, p53, and caspase knockout mice while establishing distinct roles for each of these apoptotic players, they also provided valuable information for the design of specific inhibitors of apoptosis. Thus blocking one pathway, as in caspase knockout mice, what we observe is not a complete suppression of apoptosis but rather a delay in apoptosis induction (Hakem et al., 1998; Kuida et al., 1998). In view of nature's means of ensuring activation of a compensatory apoptotic response, when one pathway fails in developing prostate cancer therapeutic interventions, the challenge remains to further dissect individual apoptotic pathways. Advances in our understanding of the integrated functions governing prostate cell proliferation and cell death, clearly suggest that effective prostate cancer therapies are not only molecularly targeted, but that are also customized to take into account the delicate balance of opposing growth influences in the ageing gland. In this review we discuss the evidence on the significance of molecular deregulation of the key players of this growth equilibrium, apoptosis and cell proliferation in prostate cancer progression, and the clinical implications of changes in the apoptotic response in disease detection and therapy.

Apoptosis in prostate carcinogenesis. A growth regulator and a therapeutic target

Development of effective therapeutic modalities for the treatment of human cancer relies heavily upon understanding the molecular alterations that result in initiation and progression of the tumorigenic process. Many of the molecular changes identified in human prostate tumorigenesis so far play key roles in apoptosis regulation. Apoptosis represents a universal and exquisitely efficient cellular suicide pathway. Since the therapeutic goal is to trigger tumor-selective apoptotic cell death (without clinically significant effects on the host), elucidation of the mechanisms underlying apoptosis deregulation will lead to the identification of specific cellular components for targeting therapeutic interventions. As our understanding of its vital role in the development and growth of the prostate gland has expanded, numerous genes that encode apoptotic regulators have been identified that are severely impaired in prostate cancer cells. In addition, the expression of apoptotic modulators within prostatic tumors appears to correlate with tumor sensitivity to traditional therapies such as hormonal ablation and radiotherapy. No strict correlation between apoptosis induction and a patient's long-term prognosis has emerged, perhaps due to the fact that the ability to achieve initial remission alone does not adequately predict long-term outcome. This review will encompass the known molecular changes intimately involved in the apoptotic pathway which have potential prognostic value in disease progression, as well as therapeutic significance in the enhancement of the apoptotic response to novel and established treatment strategies for the treatment of androgen-dependent and androgen-independent prostatic tumors. The main focus will be on the role of the transforming growth factor-beta (TGF-beta) signaling pathway, bcl-2 and the bcl-2 family members, the caspase cascade (apoptosis executioners), and the Fas pathway in induction and regulation of apoptosis following therapeutic stimuli for the management of advanced prostate cancer.

The impact of bcl-2 expression and bax deficiency on prostate homeostasis in vivo

Prostatic glandular epithelial cells undergo apoptosis in response to androgen-deprivation. The molecular determinants of androgen-responsiveness in these cells are incompletely understood. Recent evidence suggests that bcl-2 gene family members may be important in this context. We used the probasin promoter to target a human bcl-2 transgene specifically to the prostate in order to assess its impact on conferring resistance to androgen withdrawal in, otherwise sensitive, prostatic glandular epithelial cells in vivo. We examined the contribution of bax to mediating androgen-responsiveness in prostatic glandular epithelial cells using bax knockout mice. The histologic appearance of the prostates from probasin-bcl-2 transgenic mice or bax-/- mice did not differ from those of control littermates. There was no evidence of hyperplastic or neoplastic growth. There was no difference between probasin bcl-2 transgenic mice, bax-/- mice, and control littermates in steady-state levels of apoptosis. Following castration our findings suggest that both bax and bcl-2 may each contribute to the androgen-responsiveness of prostatic glandular epithelial cells. It is apparent from these results, however, that bax is not required to mediate cell death in prostatic glandular epithelial cells following castration. A comparison between the apoptotic indices in the ventral prostate from the probasin-bcl-2 and bax-/- mice following castration suggests that the presence of bcl-2 may be a more important indicator of androgen-sensitivity than a deficiency of bax.

Implications of cell death regulation in the pathogenesis and treatment of prostate cancer

Although the phenomenon of programed cell death, or apoptosis, has been recognized for many years, interest in the clinical implications of apoptotic cell death has not been widely apparent until recently. It is now established that the products of at least some oncogenes and tumor suppressor genes are able to regulate the rates of apoptosis as well as proliferation in tumor cell populations. In fact, it appears that evasion of deletion via apoptotic cell death may be a requisite event in the development of many malignant neoplasms. Molecular alterations that occur at high frequency in the pathogenesis of prostate cancer often involve genes implicated in the regulation of cell death. There is now ample reason to speculate that the susceptibility of individual malignant neoplasms to undergo apoptosis in response to a given therapeutic intervention may be a useful parameter in predicting therapeutic response. This realization has profound implications with respect to the design and implementation of treatment strategies for prostate cancer based on the biology of this disease.

The Bcl-2 gene family and apoptosis

Apoptosis, or programmed cell death, is an essential process for normal embryonic development, maintaining homeostasis in adult tissues, and suppressing carcinogenesis. The bcl-2 protein, discovered in association with follicular lymphoma, plays a prominent role in controlling apoptosis and enhancing cell survival in response to diverse apoptotic stimuli. The evolutionarily conserved bcl-2 protein is now recognized as being a member of a family of related proteins which can be categorized as death agonists or death antagonists. Progress in defining the role of bcl-2 and its family members in regulating apoptosis is rapidly advancing. This review describes, in detail, current bcl-2 family members and the possible mechanisms of function which allow the bcl-2 family of proteins to either promote or suppress cell death.

Bcl-2 suppresses apoptosis resulting from disruption of the NF-kappa B survival pathway

A role has been delineated for both bcl-2 and NF-kappa B in mediating an adaptive survival response to the TNF-alpha signaling pathway for apoptosis. Additionally, we and others have demonstrated a role for bcl-2 upregulation during progression of prostate cancer and acquisition of androgen-independent growth (T. J. McDonnell et al., 1992, Cancer Res. 52, 6940-6944). Therefore, the relationship between bcl-2 and NF-kappa B in regulating TNF-alpha-induced apoptosis was investigated in prostate carcinoma cells. Enforced overexpression of bcl-2 protein in prostatic carcinoma cells impaired TNF-alpha-mediated cytotoxicity. Expression of bcl-2 did not impose a block to, or potentiate, TNF-alpha signaling of I kappa B alpha degradation, nuclear import of the RelA p65, or NF-kappa B-dependent transactivation. Expression of two dominant-negative I kappa B alpha mutant proteins significantly enhanced TNF-alpha-induced apoptosis in control cells but not in cells expressing high levels of bcl-2 protein. Similarly, PDTC, a strong antioxidant that interferes with activation of NF-kappa B in these prostate carcinoma cells, also potentiated TNF-alpha-stimulated apoptosis signaling through a bcl-2-regulated mechanism. These findings indicate that modulation of NF-kappa B survival signaling may be used to clinical advantage in the treatment of prostate cancer patients. The efficacy of strategies proposed to enhance TNF-alpha-mediated cytotoxicity by inhibiting NF-kappa B will likely be influenced by context-dependent variables such as bcl-2 expression.

Membrane phospholipid asymmetry: host response to the externalization of phosphatidylserine

Membrane phospholipid asymmetry is an important regulator of cellular function and homeostasis. The activities of lipid transporters are contributing factors to the regulation of membrane lipid composition over the lifespan of the cell. Alterations in the activities of these proteins result in the movement of phosphatidylserine to the cell's outer leaflet. This promotes several physiologic responses including initiation of the coagulation cascade and cell recognition by the reticuloendothelial system.

Colocalization of Rh polypeptides and the aminophospholipid transporter in dilauroylphosphatidylcholine-induced erythrocyte vesicles

Cytoskeleton-free vesicles released from human red blood cells (RBC) transport exogenously supplied aminophospholipid analogues from the vesicle's outer to inner leaflet at rates comparable to those of normal RBC (Beleznay et al. (1993) Biochemistry 32, 3146-3152). Because polypeptides associated with the Rh blood group system have been implicated in the transbilayer movement of phosphatidylserine (PS), we investigated the relationship and co-localization of the aminophospholipid translocase and Rh in dilauroylphosphatidylcholine-induced RBC vesicles. The transbilayer movement of fluorescent (NBD-PS) and photoactivatable (125I-N3-PS) PS in RBC vesicles was ATP-and temperature-dependent. Inhibition of PS transport by sulfhydryl reagents could be accomplished by direct vesicle treatment or by treating RBC before vesiculation. In the case of diamide- and pyridyldithioethylamine-mediated inhibition, NBD-PS transport could be restored by reduction with dithiothreitol, indicating that the movement of the PS transporter into the emerging vesicle was independent of the oxidative status of membrane sulfhydryls. The presence of Rh polypeptides in the vesicles was verified by direct immunoprecipitation of isotopically-labeled Rh and semi-quantified by antibody adsorption assays. Similar to the movement of the PS transporter, localization of Rh polypeptides in the vesicle membrane was independent of the red cell's oxidative status. These results show that the PS translocase and Rh-related proteins colocalize in RBC vesicles suggesting that these proteins may be members of a multicomponent complex that plays a role in lipid movement and the generation of membrane lipid asymmetry.