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ABSTRACT: Oncogenic driver mutations frequently occur in lung cancer and play role in carcinogenesis. These mutations are usually associated with distinct clinical and histological features and are attractive targets for anticancer therapy. Recently, several molecularly distinct phenotypes of NSCLC based on specific and mutually exclusive genetic derangements have been described. Few targets like epidermal growth factor receptor (EGFR) mutations and anaplastic lymphoma kinase (ALK) gene rearrangements have successfully been targeted with EGFR tyrosine kinase inhibitors (TKIs) and crizotinib, respectively. Many more inhibitors of specific driver mutations involving genes like ROS, c-MET, FGFR, mTOR, IGFR and RET are currently under development. However, efforts to target some mutated genes like K-RAS have been unsuccessful. Moreover, the emerging challenge of acquired resistance to initially effective therapy is becoming another major concern. In this review recent data on novel molecular targets and their future prospects are discussed.
Current Opinion in Pharmacology 04/2013; · 6.86 Impact Factor
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ABSTRACT: The cancer stem cell model is based on a myriad of experimental and clinical observations suggesting that the malignant phenotype is sustained by a subset of cells characterized by the capacity for self-renewal, differentiation and innate resistance to chemotherapy and radiation. Cancer stem cells may be responsible for disease recurrence after definitive therapy and may therefore be functionally synonymous with minimal residual disease. Similar to other solid tumours, several putative surface markers for lung cancer stem cells have been identified, including CD133 and CD44. In addition, expression and/or activity of the cytoplasmic enzyme ALDH, and capacity of cells to exclude membrane permeable dyes (known as the "side population") correlate with stem-like function in vitro and in vivo. Embryonic stem cell pathways such as Hedgehog, Notch and WNT may also be active in lung cancers stem cells, and therefore may be therapeutically targetable for maintenance therapy in patients achieving a complete response to surgery, radiotherapy or chemotherapy. This paper will review the evidence regarding the existence and function of lung cancer stem cells in the context of the experimental and clinical evidence and discuss some ongoing controversies regarding this model.
Respirology 04/2013; · 2.42 Impact Factor
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ABSTRACT: Despite the progress achieved in breast cancer screening and therapeutic innovations, the basal-like subtype of breast cancer (BLBC) still represents a particular clinical challenge. In order to make an impact on survival in this type of aggressive breast cancer, new targeted therapeutic agents are urgently needed. Aberrant activation of the Hedgehog (Hh) signalling pathway has been unambiguously tied to cancer development and progression in a variety of solid malignancies, and the recent approval of vismodegib, an orally bioavailable small-molecule inhibitor of Smoothened, validates Hh signalling as a valuable therapeutic target. A number of recent publications have highlighted a role for Hh signalling in breast cancer models and clinical specimens. Interestingly, Hh ligand overexpression is associated with the BLBC phenotype and a poor outcome in terms of metastasis and breast cancer-related death. In this review, we provide a comprehensive overview of the canonical Hh signalling pathway in mammals, highlight its roles in mammary gland development and breast carcinogenesis and discuss its potential therapeutic value in BLBC.
Breast cancer research: BCR 03/2013; 15(2):203. · 5.24 Impact Factor
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ABSTRACT: The molecular mechanism underlying the development of Barrett's esophagus (BE), the precursor to esophageal adenocarcinoma (EAC) remains unknown. Our previous work implicated sonic hedgehog (Shh) signaling as a possible driver of BE via bone morphogenic protein 4 (Bmp4) and Sox9. Here we have utilized a novel in vivo tissue reconstitution model to investigate the relative roles of Bmp4 and Sox9 in driving metaplasia. Epithelia reconstituted from squamous epithelial cells or empty vector (EV) transduced cells had a stratified squamous phenotype, reminiscent of normal esophagus. Expression of Bmp4 in the stromal compartment activated signaling in the epithelium but did not alter the squamous phenotype. In contrast, expression of Sox9 in squamous epithelial cells induced formation of columnar-like epithelium with expression of the columnar differentiation marker Ck8 and the intestinal specific glycoprotein, A33. In patient tissue, A33 protein was expressed specifically in BE and not normal esophagus. Expression of Cdx2, another putative driver of BE alone had no affect on reconstitution of a squamous epithelium. Furthermore, epithelium co-expressing Cdx2 and Sox9 had a similar phenotype to epithelium expressing Sox9 alone. Our results demonstrate that Sox9 is sufficient to drive columnar differentiation of squamous epithelium and expression of an intestinal differentiation marker, reminiscent of BE. These data suggest that Shh-mediated expression of Sox9 may be an important early event in the development of BE, and that the potential for inhibitors of the hedgehog signaling pathway to be used in the treatment of BE and/or EAC could be tested in the near future.
AJP Gastrointestinal and Liver Physiology 10/2012; · 3.43 Impact Factor
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Kwon-Sik Park,
Luciano G Martelotto,
Martin Peifer,
Martin L Sos,
Anthony N Karnezis,
Moe R Mahjoub,
Katie Bernard,
Jamie F Conklin,
Anette Szczepny,
Jing Yuan, [......],
Wendy L Devereux,
Cory A Ocasio,
James K Chen,
Tim Stearns,
Roman K Thomas,
Marion Dorsch,
Silvia Buonamici, D Neil Watkins,
Craig D Peacock,
Julien Sage
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ABSTRACT: Small-cell lung cancer (SCLC) is an aggressive neuroendocrine subtype of lung cancer for which there is no effective treatment. Using a mouse model in which deletion of Rb1 and Trp53 in the lung epithelium of adult mice induces SCLC, we found that the Hedgehog signaling pathway is activated in SCLC cells independently of the lung microenvironment. Constitutive activation of the Hedgehog signaling molecule Smoothened (Smo) promoted the clonogenicity of human SCLC in vitro and the initiation and progression of mouse SCLC in vivo. Reciprocally, deletion of Smo in Rb1 and Trp53-mutant lung epithelial cells strongly suppressed SCLC initiation and progression in mice. Furthermore, pharmacological blockade of Hedgehog signaling inhibited the growth of mouse and human SCLC, most notably following chemotherapy. These findings show a crucial cell-intrinsic role for Hedgehog signaling in the development and maintenance of SCLC and identify Hedgehog pathway inhibition as a therapeutic strategy to slow the progression of disease and delay cancer recurrence in individuals with SCLC.
Nature medicine 10/2011; 17(11):1504-8. · 27.14 Impact Factor
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ABSTRACT: The Hedgehog (Hh) pathway is a conserved signalling system essential for embryonic development and for the maintenance of self-renewal pathways in progenitor cells. Mutations that deregulate Hh signalling are directly implicated in basal cell carcinoma and medulloblastoma. The mechanisms of Hh pathway activation in cancers in which no pathway mutations have been identified are less clear, but of great translational significance. Small molecule inhibitors of the pathway, many of which are in early phase clinical trials, may shed further light on this question. Canonical Hh signalling promotes the expression of target genes through the Glioma-associated oncogene (GLI) transcription factors. There is now increasing evidence suggesting that 'non-canonical' Hh signalling mechanisms, some of which are independent of GLI-mediated transcription, may be important in cancer and development. The focus of this review is to summarise some of the known mechanisms of Hh signalling as well as its emerging role in cancer.
Growth factors (Chur, Switzerland) 08/2011; 29(6):221-34. · 2.47 Impact Factor
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Sandra A O'Toole,
Dorothy A Machalek,
Robert F Shearer,
Ewan K A Millar,
Radhika Nair,
Peter Schofield,
Duncan McLeod,
Caroline L Cooper,
Catriona M McNeil,
Andrea McFarland, [......],
Min Ru Qiu,
Brian Rabinovich,
Luciano G Martelotto,
Duc Vu,
Gregory E Hannigan,
Elizabeth A Musgrove,
Daniel Christ,
Robert L Sutherland, D Neil Watkins,
Alexander Swarbrick
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ABSTRACT: Hedgehog (Hh) signaling plays an important role in several malignancies but its clinical significance in breast cancer is unclear. In a cohort of 279 patients with invasive ductal carcinoma of the breast, expression of Hh ligand was significantly associated with increased risk of metastasis, breast cancer-specific death, and a basal-like phenotype. A paracrine signature, encompassing high epithelial Hh ligand and high stromal Gli1, was an independent predictor for overall survival in multivariate analysis. In 2 independent histological progression series (n = 301), Hh expression increased with atypia. Hh ligand overexpression in a mouse model of basal breast cancer increased growth, induced a poorly differentiated phenotype, accelerated metastasis, and reduced survival. A stromal requirement for these effects was supported by the lack of similar Hh-mediated changes in vitro, and by stromal-specific expression of Hh target genes in vivo. Furthermore, inhibition of Hh ligand with a monoclonal antibody (5E1) inhibited tumor growth and metastasis. These data suggest that epithelial-stromal Hh signaling, driven by ligand expression in carcinoma cells, promotes breast cancer growth and metastasis. Blockade of Hh signaling to peritumoral stromal cells may represent a novel therapeutic approach in some basal-like breast cancers.
Cancer Research 06/2011; 71(11):4002-14. · 7.86 Impact Factor
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Silvia Buonamici,
Juliet Williams,
Michael Morrissey,
Anlai Wang,
Ribo Guo,
Anthony Vattay,
Kathy Hsiao,
Jing Yuan,
John Green,
Beatriz Ospina, [......],
Xu Wu,
Sauveur-Michel Maira,
Carlos García-Echeverría,
Kimberly J Briggs, D Neil Watkins,
Yung-mae Yao,
Christoph Lengauer,
Markus Warmuth,
William R Sellers,
Marion Dorsch
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ABSTRACT: The malignant brain cancer medulloblastoma is characterized by mutations in Hedgehog (Hh) signaling pathway genes, which lead to constitutive activation of the G protein (heterotrimeric guanosine triphosphate-binding protein)-coupled receptor Smoothened (Smo). The Smo antagonist NVP-LDE225 inhibits Hh signaling and induces tumor regression in animal models of medulloblastoma. However, evidence of resistance was observed during the course of treatment. Molecular analysis of resistant tumors revealed several resistance mechanisms. We noted chromosomal amplification of Gli2, a downstream effector of Hh signaling, and, more rarely, point mutations in Smo that led to reactivated Hh signaling and restored tumor growth. Analysis of pathway gene expression signatures also, unexpectedly, identified up-regulation of phosphatidylinositol 3-kinase (PI3K) signaling in resistant tumors as another potential mechanism of resistance. Probing the relevance of increased PI3K signaling, we demonstrated that addition of the PI3K inhibitor NVP-BKM120 or the dual PI3K-mTOR (mammalian target of rapamycin) inhibitor NVP-BEZ235 to the initial treatment with the Smo antagonist markedly delayed the development of resistance. Our findings may be useful in informing treatment strategies for medulloblastoma.
Science translational medicine 09/2010; 2(51):51ra70. · 7.80 Impact Factor
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David H Wang,
Nicholas J Clemons,
Tomoharu Miyashita,
Adam J Dupuy,
Wei Zhang,
Anette Szczepny,
Ian M Corcoran-Schwartz,
Daniel L Wilburn,
Elizabeth A Montgomery,
Jean S Wang,
Nancy A Jenkins,
Neal A Copeland,
John W Harmon,
Wayne A Phillips, D Neil Watkins
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ABSTRACT: The molecular mechanism underlying epithelial metaplasia in Barrett's esophagus remains unknown. Recognizing that Hedgehog signaling is required for early esophageal development, we sought to determine if the Hedgehog pathway is reactivated in Barrett's esophagus, and if genes downstream of the pathway could promote columnar differentiation of esophageal epithelium.
Immunohistochemistry, immunofluorescence, and quantitative real-time polymerase chain reaction were used to analyze clinical specimens, human esophageal cell lines, and mouse esophagi. Human esophageal squamous epithelial (HET-1A) and adenocarcinoma (OE33) cells were subjected to acid treatment and used in transfection experiments. Swiss Webster mice were used in a surgical model of bile reflux injury. An in vivo transplant culture system was created using esophageal epithelium from Sonic hedgehog transgenic mice.
Marked up-regulation of Hedgehog ligand expression, which can be induced by acid or bile exposure, occurs frequently in Barrett's epithelium and is associated with stromal expression of the Hedgehog target genes PTCH1 and BMP4. BMP4 signaling induces expression of SOX9, an intestinal crypt transcription factor, which is highly expressed in Barrett's epithelium. We further show that expression of Deleted in Malignant Brain Tumors 1, the human homologue of the columnar cell factor Hensin, occurs in Barrett's epithelium and is induced by SOX9. Finally, transgenic expression of Sonic hedgehog in mouse esophageal epithelium induces expression of stromal Bmp4, epithelial Sox9, and columnar cytokeratins.
Epithelial Hedgehog ligand expression may contribute to the initiation of Barrett's esophagus through induction of stromal BMP4, which triggers reprogramming of esophageal epithelium in favor of a columnar phenotype.
Gastroenterology 02/2010; 138(5):1810-22. · 11.68 Impact Factor
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ABSTRACT: Angiogenesis is the formation of neovasculature from a pre-existing vascular network. Progression of solid tumors including lung cancer is angiogenesis-dependent. We previously introduced a bioinformatics-based methodology to identify endogenous anti-angiogenic peptide sequences, and validated these predictions in vitro in human umbilical vein endothelial cell (HUVEC) proliferation and migration assays.
One family of peptides with high activity is derived from the alpha-fibrils of type IV collagen. Based on the results from the in vitro screening, we have evaluated the ability of a 20 amino acid peptide derived from the alpha5 fibril of type IV collagen, pentastatin-1, to suppress vessel growth in an angioreactor-based directed in vivo angiogenesis assay (DIVAA). In addition, pentastatin-1 suppressed tumor growth with intraperitoneal peptide administration in a small cell lung cancer (SCLC) xenograft model in nude mice using the NCI-H82 human cancer cell line.
Pentastatin-1 decreased the invasion of vessels into angioreactors in vivo in a dose dependent manner. The peptide also decreased the rate of tumor growth and microvascular density in vivo in a small cell lung cancer xenograft model.
The peptide treatment significantly decreased the invasion of microvessels in angioreactors and the rate of tumor growth in the xenograft model, indicating potential treatment for angiogenesis-dependent disease, and for translational development as a therapeutic agent for lung cancer.
BMC Cancer 01/2010; 10:29. · 3.01 Impact Factor
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Tara L Lin,
Qiuju H Wang,
Patrick Brown,
Craig Peacock,
Akil A Merchant,
Sarah Brennan,
Evan Jones,
Karen McGovern, D Neil Watkins,
Kathleen M Sakamoto,
William Matsui
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ABSTRACT: Conserved embryonic signaling pathways such as Hedgehog (Hh), Wingless and Notch have been implicated in the pathogenesis of several malignancies. Recent data suggests that Hh signaling plays a role in normal B-cell development, and we hypothesized that Hh signaling may be important in precursor B-cell acute lymphocytic leukemia (B-ALL). We found that the expression of Hh pathway components was common in human B-ALL cell lines and clinical samples. Moreover, pathway activity could be modulated by Hh ligand or several pathway inhibitors including cyclopamine and the novel SMOOTHENED (SMO) inhibitor IPI-926. The inhibition of pathway activity primarily impacted highly clonogenic B-ALL cells expressing aldehyde dehydrogenase (ALDH) by limiting their self-renewal potential both in vitro and in vivo. These data demonstrate that Hh pathway activation is common in B-ALL and represents a novel therapeutic target regulating self-renewal and persistence of the malignant clone.
PLoS ONE 01/2010; 5(12):e15262. · 4.09 Impact Factor
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ABSTRACT: Drug carrier particles composed of poly(ethylene glycol)-co-poly(sebacic acid) (PEG-PSA) have been shown capable of efficient aerosolization into model lungs and the ability to rapidly penetrate human mucus. Here, we develop PEG-PSA particles (Etop/PEG-PSA) that encapsulate up to 40% etoposide by weight in a one step process, release it continuously for 6 days in vitro, and maintain its cytotoxic activity against a human lung tumor cell line in vitro. We further show that Etop/PEG-PSA injected intratumorally effectively suppress human lung tumor growth in a xenograft mouse model, with 100% survival after 31 days. In contrast, 0% survival was observed by day 24 in animals that received free etoposide (either intratumoral or intraperitoneal administration) or placebo particles intratumorally. These findings support PEG-PSA as a drug delivery platform for improved local therapy of cancer.
Biomaterials 09/2009; 31(2):339-44. · 7.40 Impact Factor
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Vincent C Daniel,
Luigi Marchionni,
Jared S Hierman,
Jonathan T Rhodes,
Wendy L Devereux,
Charles M Rudin,
Rex Yung,
Giovanni Parmigiani,
Marion Dorsch,
Craig D Peacock, D Neil Watkins
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ABSTRACT: Traditional approaches to the preclinical investigation of cancer therapies rely on the use of established cell lines maintained in serum-based growth media. This is particularly true of small-cell lung cancer (SCLC), where surgically resected tissue is rarely available. Recent attention has focused on the need for better models that preserve the integrity of cancer stem cell populations, as well as three-dimensional tumor-stromal interactions. Here we describe a primary xenograft model of SCLC in which endobronchial tumor specimens obtained from chemo-naive patients are serially propagated in vivo in immunodeficient mice. In parallel, cell lines grown in conventional tissue culture conditions were derived from each xenograft line, passaged for 6 months, and then reimplanted to generate secondary xenografts. Using the Affymetrix platform, we analyzed gene expression in primary xenograft, xenograft-derived cell line, and secondary xenograft, and compared these data to similar analyses of unrelated primary SCLC samples and laboratory models. When compared with normal lung, primary tumors, xenografts, and cell lines displayed a gene expression signature specific for SCLC. Comparison of gene expression within the xenograft model identified a group of tumor-specific genes expressed in primary SCLC and xenografts that was lost during the transition to tissue culture and that was not regained when the tumors were reestablished as secondary xenografts. Such changes in gene expression may be a common feature of many cancer cell culture systems, with functional implications for the use of such models for preclinical drug development.
Cancer Research 05/2009; 69(8):3364-73. · 7.86 Impact Factor
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ABSTRACT: Hypermethylated in cancer-1 (HIC1) is a tumor suppressor frequently targeted for promoter hypermethylation in medulloblastoma, an embryonal tumor of the cerebellum. Recently, we showed that HIC1 is a direct transcriptional repressor of ATOH1, a proneural transcription factor required for normal cerebellar development, as well as for medulloblastoma cell viability. Because demethylating agents can induce reexpression of silenced tumor suppressors, restoring HIC1 function may present an attractive therapeutic avenue in medulloblastoma by exploiting an apparent addiction to ATOH1.
Cancer Research 12/2008; 68(21):8654-6. · 7.86 Impact Factor
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ABSTRACT: Lung cancer is the leading cause of cancer death in the world today and is poised to claim approximately 1 billion lives during the 21st century. A major challenge in treating this and other cancers is the intrinsic resistance to conventional therapies demonstrated by the stem/progenitor cell that is responsible for the sustained growth, survival, and invasion of the tumor. Identifying these stem cells in lung cancer and defining the biologic processes necessary for their existence is paramount in developing new clinical approaches with the goal of preventing disease recurrence. This review summarizes our understanding of the cellular and molecular mechanisms operating within the putative cancer-initiating cell at the core of lung neoplasia.
Journal of Clinical Oncology 07/2008; 26(17):2883-9. · 18.37 Impact Factor
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Wei Zhang,
Sabine C Glöckner,
Mingzhou Guo,
Emi Ota Machida,
David H Wang,
Hariharan Easwaran,
Leander Van Neste,
James G Herman,
Kornel E Schuebel, D Neil Watkins,
Nita Ahuja,
Stephen B Baylin
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ABSTRACT: SRY-box containing gene 17 (Sox17) is a member of the high mobility group (HMG) transcription factor superfamily, which plays critical roles in the regulation of development and stem/precursor cell function, at least partly through repression of Wnt pathway activity. Modulators controlling aberrant Wnt signaling activation are frequently disrupted in human cancers through complementary effects of epigenetic and genetic changes. Our recent global analysis of CpG island hypermethylation and gene expression in colorectal cancer (CRC) cell lines revealed that SOX17 gene silencing is associated with DNA hypermethylation of a CpG island in the promoter region. Here, we report that CpG island methylation-dependent silencing of SOX17 occurs in 100% of CRC cell lines, 86% of colorectal adenomas, 100% of stage I and II CRC, 89% of stage III CRC, 89% of primary esophageal cancer, and 50% of non-small cell lung cancer. Overexpression of SOX17 in HCT116 CRC cells inhibits colony growth and beta-catenin/T-cell factor-dependent transcription. Structure-based deletion analysis further shows the presence of a Wnt signaling repression domain in the SOX17 HMG box. Together, our studies suggest that SOX17 is a negative modulator of canonical Wnt signaling, and that SOX17 silencing due to promoter hypermethylation is an early event during tumorigenesis and may contribute to aberrant activation of Wnt signaling in CRC.
Cancer Research 05/2008; 68(8):2764-72. · 7.86 Impact Factor
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Christine L Hann,
Vincent C Daniel,
Elizabeth A Sugar,
Irina Dobromilskaya,
Sara C Murphy,
Leslie Cope,
Xue Lin,
Jared S Hierman,
Daniel L Wilburn, D Neil Watkins,
Charles M Rudin
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ABSTRACT: Bcl-2 is a central regulator of cell survival that is overexpressed in the majority of small cell lung cancers (SCLC) and contributes to both malignant transformation and therapeutic resistance. We compared primary SCLC xenografts prepared from de novo human tumors with standard cell line-based xenografts in the evaluation of a novel and highly potent small molecule inhibitor of Bcl-2, ABT-737. ABT-737 induced dramatic regressions in tumors derived from some SCLC cell lines. In contrast, only one of three primary xenograft SCLC tumors showed significant growth inhibition with ABT-737. Explanations for this apparent dichotomy may include relatively low expression of Bcl-2 in the primary xenografts or inherent differences in the model systems. The addition of etoposide to ABT-737 in the primary xenografts resulted in significant decreases in tumor growth, underscoring the clinical potential of ABT-737 in combination therapy. To identify factors that may contribute to resistance to ABT-737 and related inhibitors, we isolated resistant derivatives of an initially sensitive cell line-based xenograft. Acquired resistance in this model was associated with decreases in the expression of the primary target Bcl-2, of proapoptotic partners of Bcl-2 (Bax and Bim), and of Bcl-2:Bim heterodimers. Expression profiling reveals 85 candidate genes demonstrating consistent changes in gene expression with acquired resistance. Taken together, these data have specific implications for the clinical development of Bcl-2 inhibitors for SCLC and broader implications for the testing of novel anticancer strategies in relevant preclinical models.
Cancer Research 05/2008; 68(7):2321-8. · 7.86 Impact Factor
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ABSTRACT: A diagnosis of small cell lung cancer (SCLC) today confers essentially the same terrible prognosis that it did 25 years ago, when common use of cisplatin-based chemotherapy began for this disease. In contrast to past decades of research on many other solid tumors, studies of combination chemotherapy using later generation cytotoxics and targeted kinase inhibitors have not had a significant impact on standard care for SCLC. The past few years have seen suggestions of incrementally improved outcomes using standard cytotoxics, including cisplatin-based combination studies of irinotecan and amrubicin by Japanese research consortia. Confirmatory phase III studies of these agents are ongoing in the United States. Antiangiogenic strategies are also of primary interest and are in late-phase testing. Several novel therapeutics, including high-potency small molecule inhibitors of Bcl-2 and the Hedgehog signaling pathway, and a recently discovered replication-competent picornavirus, have shown remarkable activity against SCLC in preclinical models and are currently in simultaneous phase I clinical development. Novel therapeutic approaches based on advances in understanding of the biology of SCLC have the potential to radically change the outlook for patients with this disease.
Journal of the National Comprehensive Cancer Network: JNCCN 04/2008; 6(3):315-22. · 4.41 Impact Factor
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ABSTRACT: Medulloblastoma is an embryonal tumor thought to arise from the granule cell precursors (GCPs) of the cerebellum. PATCHED (PTCH), an inhibitor of Hedgehog signaling, is the best-characterized tumor suppressor in medulloblastoma. However, <20% of medulloblastomas have mutations in PTCH. In the search for other tumor suppressors, interest has focused on the deletion events at the 17p13.3 locus, the most common genetic defect in medulloblastoma. This chromosomal region contains HYPERMETHYLATED IN CANCER 1 (HIC1), a transcriptional repressor that is a frequent target of epigenetic gene silencing in medulloblastoma. Here we use a mouse model of Ptch1 heterozygosity to reveal a critical tumor suppressor function for Hic1 in medulloblastoma. When compared with Ptch1 heterozygous mutants, compound Ptch1/Hic1 heterozygotes display a fourfold increased incidence of medulloblastoma. We show that Hic1 is a direct transcriptional repressor of Atonal Homolog 1 (Atoh1), a proneural transcription factor essential for cerebellar development, and show that ATOH1 expression is required for human medulloblastoma cell growth in vitro. Given that Atoh1 is also a putative target of Hh signaling, we conclude that the Hic1 and Ptch1 tumor suppressors cooperate to silence Atoh1 expression during a critical phase in GCP differentiation in which malignant transformation may lead to medulloblastoma.
Genes & Development 03/2008; 22(6):770-85. · 11.66 Impact Factor
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William Matsui,
Qiuju Wang,
James P Barber,
Sarah Brennan,
B Douglas Smith,
Ivan Borrello,
Ian McNiece,
Lan Lin,
Richard F Ambinder,
Craig Peacock, D Neil Watkins,
Carol Ann Huff,
Richard J Jones
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ABSTRACT: Many agents are active in multiple myeloma, but the majority of patients relapse. This clinical pattern suggests most cancer cells are eliminated, but cells with the clonogenic potential to mediate tumor regrowth are relatively chemoresistant. Our previous data suggested that CD138(+) multiple myeloma plasma cells cannot undergo long-term proliferation but rather arise from clonogenic CD138(neg) B cells. We compared the relative sensitivity of these distinct cell types to clinical antimyeloma agents and found that dexamethasone, lenadilomide, bortezomib, and 4-hydroxycyclophosphamide inhibited CD138(+) multiple myeloma plasma cells but had little effect on CD138(neg) precursors in vitro. We further characterized clonogenic multiple myeloma cells and stained cell lines using the Hoechst side population and Aldefluor assays. Each assay identified CD138(neg) cells suggesting that they possess high drug efflux capacity and intracellular drug detoxification activity. We also found that multiple myeloma cells expressing the memory B-cell markers CD20 and CD27 could give rise to clonogenic multiple myeloma growth in vitro and engraft immunodeficient nonobese diabetes/severe combined immunodeficient mice during both primary and secondary transplantation. Furthermore, both the side population and Aldefluor assays were capable of identifying circulating clonotypic memory B-cell populations within the peripheral blood of multiple myeloma patients. Our results suggest that circulating clonotypic B-cell populations represent multiple myeloma stem cells, and the relative drug resistance of these cells is mediated by processes that protect normal stem cells from toxic injury.
Cancer Research 02/2008; 68(1):190-7. · 7.86 Impact Factor
