Ligand-dependent hedgehog signaling maintains an undifferentiated, malignant osteosarcoma phenotype

TP53 and RB1 loss-of-function mutations are common in osteosarcoma. During development, combined loss of TP53 and RB1 function leads to downregulation of autophagy and the aberrant formation of primary cilia, cellular organelles essential for the transmission of canonical Hedgehog (Hh) signaling. Excess cilia formation then leads to hypersensitivity to Hedgehog (Hh) ligand signaling. In mouse and human models, we now show that osteosarcomas with mutations in TP53 and RB1 exhibit enhanced ligand-dependent Hh pathway activation through Smoothened (SMO), a transmembrane signaling molecule required for activation of the canonical Hh pathway. This dependence is mediated by hypersensitivity to Hh ligand and is accompanied by impaired autophagy and increased primary cilia formation and expression of Hh ligand in vivo. Using a conditional genetic mouse model of Trp53 and Rb1 inactivation in osteoblast progenitors, we further show that deletion of Smo converts the highly malignant osteosarcoma phenotype to benign, well differentiated bone tumors. Conversely, conditional overexpression of SHH ligand, or a gain-of-function SMO mutant in committed osteoblast progenitors during development blocks terminal bone differentiation. Finally, we demonstrate that the SMO antagonist sonidegib (LDE225) induces growth arrest and terminal differentiation in vivo in osteosarcomas that express primary cilia and Hh ligand combined with mutations in TP53. These results provide a mechanistic framework for aberrant Hh signaling in osteosarcoma based on defining mutations in the tumor suppressor, TP53.

MYC drives platinum resistant SCLC that is overcome by the dual PI3K-HDAC inhibitor fimepinostat

BACKGROUND

Small cell lung cancer (SCLC) is an aggressive neuroendocrine cancer with an appalling overall survival of less than 5% (Zimmerman et al. J Thor Oncol 14:768-83, 2019). Patients typically respond to front line platinum-based doublet chemotherapy, but almost universally relapse with drug resistant disease. Elevated MYC expression is common in SCLC and has been associated with platinum resistance. This study evaluates the capacity of MYC to drive platinum resistance and through screening identifies a drug capable of reducing MYC expression and overcoming resistance.

METHODS

Elevated MYC expression following the acquisition of platinum resistance in vitro and in vivo was assessed. Moreover, the capacity of enforced MYC expression to drive platinum resistance was defined in SCLC cell lines and in a genetically engineered mouse model that expresses MYC specifically in lung tumors. High throughput drug screening was used to identify drugs able to kill MYC-expressing, platinum resistant cell lines. The capacity of this drug to treat SCLC was defined in vivo in both transplant models using cell lines and patient derived xenografts and in combination with platinum and etoposide chemotherapy in an autochthonous mouse model of platinum resistant SCLC.

RESULTS

MYC expression is elevated following the acquisition of platinum resistance and constitutively high MYC expression drives platinum resistance in vitro and in vivo. We show that fimepinostat decreases MYC expression and that it is an effective single agent treatment for SCLC in vitro and in vivo. Indeed, fimepinostat is as effective as platinum-etoposide treatment in vivo. Importantly, when combined with platinum and etoposide, fimepinostat achieves a significant increase in survival.

CONCLUSIONS

MYC is a potent driver of platinum resistance in SCLC that is effectively treated with fimepinostat.

Deletion of kif3a in CK19 positive cells leads to primary cilia loss, biliary cell proliferation and cystic liver lesions in TAA-treated mice

BACKGROUND & AIMS

Loss of primary cilia in epithelial cells is known to cause cystic diseases of the liver and kidney. We have previously shown that during experimental and human cirrhosis that primary cilia were predominantly expressed on biliary cells in the ductular reaction. However, the role of primary cilia in the pathogenesis of the ductular reaction is not fully understood.

METHODS

Primary cilia were specifically removed in biliary epithelial cells (BECs) by the administration of tamoxifen to Kif3a^f/f;CK19^CreERT mice at week 2 of a 20-week course of TAA treatment. Biliary progenitor cells were isolated and grown as organoids from gallbladders. Cells and tissue were analysed using histology, immunohistochemistry and Western blot assays.

RESULTS

At the end of 20 weeks TAA administration, primary cilia loss in liver BECs resulted in multiple microscopic cystic lesions within an unaltered ductular reaction. These were not seen in control mice who did not receive TAA. There was no effect of biliary primary cilia loss on the development of cirrhosis. Increased cellular proliferation was seen within the cystic structures associated with a decrease in hepatocyte lobular proliferation. Loss of primary cilia within biliary organoids was initially associated with reduced cell passage survival but this inhibitory effect was diminished in later passages. ERK but not WNT signalling was enhanced in primary cilia loss-induced cystic lesions in vivo and its inhibition reduced the expansion of primary cilia deficient biliary progenitor cells in vitro.

CONCLUSIONS

TAA-treated kif3a BEC-specific knockout mice had an unaltered progression to cirrhosis, but developed cystic lesions that showed increased proliferation.

Lineage-restricted neoplasia driven by Myc defaults to small cell lung cancer when combined with loss of p53 and Rb in the airway epithelium

Small cell lung cancer (SCLC) is an aggressive neuroendocrine cancer characterized by loss of function TP53 and RB1 mutations in addition to mutations in other oncogenes including MYC. Overexpression of MYC together with Trp53 and Rb1 loss in pulmonary neuroendocrine cells of the mouse lung drives an aggressive neuroendocrine low variant subtype of SCLC. However, the transforming potential of MYC amplification alone on airway epithelium is unclear. Therefore, we selectively and conditionally overexpressed MYC stochastically throughout the airway or specifically in neuroendocrine, club, or alveolar type II cells in the adult mouse lung. We observed that MYC overexpression induced carcinoma in situ which did not progress to invasive disease. The formation of adenoma or SCLC carcinoma in situ was dependent on the cell of origin. In contrast, MYC overexpression combined with conditional deletion of both Trp53 and Rb1 exclusively gave rise to SCLC, irrespective of the cell lineage of origin. However, cell of origin influenced disease latency, metastatic potential, and the transcriptional profile of the SCLC phenotype. Together this reveals that MYC overexpression alone provides a proliferative advantage but when combined with deletion of Trp53 and Rb1 it facilitates the formation of aggressive SCLC from multiple cell lineages.

A non-genetic, cell cycle-dependent mechanism of platinum resistance in lung adenocarcinoma

We previously used a pulse-based in vitro assay to unveil targetable signalling pathways associated with innate cisplatin resistance in lung adenocarcinoma (Hastings et al., 2020). Here, we advanced this model system and identified a non-genetic mechanism of resistance that drives recovery and regrowth in a subset of cells. Using RNAseq and a suite of biosensors to track single-cell fates both in vitro and in vivo, we identified that early S phase cells have a greater ability to maintain proliferative capacity, which correlated with reduced DNA damage over multiple generations. In contrast, cells in G1, late S or those treated with PARP/RAD51 inhibitors, maintained higher levels of DNA damage and underwent prolonged S/G2 phase arrest and senescence. Combined with our previous work, these data indicate that there is a non-genetic mechanism of resistance in human lung adenocarcinoma that is dependent on the cell cycle stage at the time of cisplatin exposure.

Trp53 and Rb1 regulate autophagy and ligand-dependent Hedgehog signaling

Ligand-dependent activation of Hedgehog (Hh) signaling in cancer occurs without mutations in canonical pathway genes. Consequently, the genetic basis of Hh pathway activation in adult solid tumors, such as small-cell lung cancer (SCLC), is unknown. Here we show that combined inactivation of Trp53 and Rb1, a defining genetic feature of SCLC, leads to hypersensitivity to Hh ligand in vitro, and during neural tube development in vivo. This response is associated with the aberrant formation of primary cilia, an organelle essential for canonical Hh signaling through smoothened, a transmembrane protein targeted by small-molecule Hh inhibitors. We further show that loss of both Trp53 and Rb1 disables transcription of genes in the autophagic machinery necessary for the degradation of primary cilia. In turn, we also demonstrate a requirement for Kif3a, a gene essential for the formation of primary cilia, in a mouse model of SCLC induced by conditional deletion of both Trp53 and Rb1 in the adult airway. Our results provide a mechanistic framework for therapeutic targeting of ligand-dependent Hh signaling in human cancers with somatic mutations in both TP53 and RB1.

p53 and RB1 regulate Hedgehog responsiveness via autophagy-mediated ciliogenesis

Loss of tumor protein p53 (p53) and RB transcriptional corepressor 1 (RB1) in developmental and small cell lung cancer models promotes primary cilia formation and hyper-responsiveness to Hedgehog ligand. This is mediated by impaired transcription of p53 and RB1 target genes involved in autophagic degradation of primary cilia.

Analysis of pulsed cisplatin signalling dynamics identifies effectors of resistance in lung adenocarcinoma

The identification of clinically viable strategies for overcoming resistance to platinum chemotherapy in lung adenocarcinoma has previously been hampered by inappropriately tailored in vitro assays of drug response. Therefore, using a pulse model that closely mimics the in vivo pharmacokinetics of platinum therapy, we profiled cisplatin-induced signalling, DNA-damage and apoptotic responses across a panel of human lung adenocarcinoma cell lines. By coupling this data to real-time, single-cell imaging of cell cycle and apoptosis we provide a fine-grained stratification of response, where a P70S6K-mediated signalling axis promotes resistance on a TP53 wildtype or null background, but not a mutant TP53 background. This finding highlights the value of in vitro models that match the physiological pharmacokinetics of drug exposure. Furthermore, it also demonstrates the importance of a mechanistic understanding of the interplay between somatic mutations and the signalling networks that govern drug response for the implementation of any consistently effective, patient-specific therapy.

Lung adenocarcinoma is the most common type of lung cancer, and it emerges because of a variety of harmful genetic changes, or mutations. Two lung cancer patients – or indeed, two different sets of cancerous cells within a patient – may therefore carry different damaging mutations.

A group of drugs called platinum-based chemotherapies are currently the most effective way to treat lung adenocarcinoma. Yet, only 30% of patients actually respond to the therapy. Many studies conducted in laboratory settings have tried to understand why most cases are resistant to treatment, with limited success.

Here, Hastings, Gonzalez-Rajal et al. propose that previous research has been inconclusive because studies done in the laboratory do not reflect how the treatment is actually administered. In patients, platinum-based drugs are cleared from the body within a few hours, but during experiments, the treatment is continually administered to cells growing in a dish.

Hastings, Gonzalez-Rajal et al. therefore developed a laboratory method that mimics the way cells are exposed to platinum-based chemotherapy in the body. These experiments showed that the lung adenocarcinoma cells which resisted treatment also carried high levels of a protein known as P70S6K. Pairing platinum-based chemotherapy with a drug that blocks the activity of P70S6K killed these resistant cells. This combination also treated human lung adenocarcinoma tumours growing under the skin of mice. However, it was ineffective on cancerous cells that carry a mutation in a protein called p53, which is often defective in cancers.

Overall, this work demonstrates the need to refine how drugs are tested in the laboratory to better reflect real-life conditions. It also underlines the importance of personalizing drug combinations to the genetic background of each tumour, a concept that will be vital to consider in future clinical trials.

ADAM17 selectively activates the IL-6 trans-signaling/ERK MAPK axis in KRAS-addicted lung cancer

Oncogenic KRAS mutations are major drivers of lung adenocarcinoma (LAC), yet the direct therapeutic targeting of KRAS has been problematic. Here, we reveal an obligate requirement by oncogenic KRAS for the ADAM17 protease in LAC In genetically engineered and xenograft (human cell line and patient-derived) Kras ^G12D-driven LAC models, the specific blockade of ADAM17, including with a non-toxic prodomain inhibitor, suppressed tumor burden by reducing cellular proliferation. The pro-tumorigenic activity of ADAM17 was dependent upon its threonine phosphorylation by p38 MAPK, along with the preferential shedding of the ADAM17 substrate, IL-6R, to release soluble IL-6R that drives IL-6 trans-signaling via the ERK1/2 MAPK pathway. The requirement for ADAM17 in Kras ^G12D-driven LAC was independent of bone marrow-derived immune cells. Furthermore, in KRAS mutant human LAC, there was a significant positive correlation between augmented phospho-ADAM17 levels, observed primarily in epithelial rather than immune cells, and activation of ERK and p38 MAPK pathways. Collectively, these findings identify ADAM17 as a druggable target for oncogenic KRAS-driven LAC and provide the rationale to employ ADAM17-based therapeutic strategies for targeting KRAS mutant cancers.

GEAMP, a novel gastroesophageal junction carcinoma cell line derived from a malignant pleural effusion

Gastroesophageal junction (GEJ) cancer remains a clinically significant disease in Western countries due to its increasing incidence, which mirrors that of esophageal cancer, and poor prognosis. To develop novel and effective approaches for prevention, early detection, and treatment of patients with GEJ cancer, a better understanding of the mechanisms driving pathogenesis and malignant progression of this disease is required. These efforts have been limited by the small number of available cell lines and appropriate preclinical animal models for in vitro and in vivo studies. We have established and characterized a novel GEJ cancer cell line, GEAMP, derived from the malignant pleural effusion of a previously treated GEJ cancer patient. Comprehensive genetic analyses confirmed a clonal relationship between GEAMP cells and the primary tumor. Targeted next-generation sequencing identified 56 nonsynonymous alterations in 51 genes including TP53 and APC, which are commonly altered in GEJ cancer. In addition, multiple copy-number alterations were found including EGFR and K-RAS gene amplifications and loss of CDKN2A and CDKN2B. Histological examination of subcutaneous flank xenografts in nude and NOD-SCID mice showed a carcinoma with mixed squamous and glandular differentiation, suggesting GEAMP cells contain a subpopulation with multipotent potential. Finally, pharmacologic inhibition of the EGFR signaling pathway led to downregulation of key downstream kinases and inhibition of cell proliferation in vitro. Thus, GEAMP represents a valuable addition to the limited number of bona fide GEJ cancer cell lines.

Renal epithelial cells retain primary cilia during human acute renal allograft rejection injury

Objectives

Primary cilia are sensory organelles which co-ordinate several developmental/repair pathways including hedgehog signalling. Studies of human renal allografts suffering acute tubular necrosis have shown that length of primary cilia borne by epithelial cells doubles throughout the nephron and collecting duct, and then normalises as renal function returns. Conversely the loss of primary cilia has been reported in chronic allograft rejection and linked to defective hedgehog signalling. We investigated the fate of primary cilia in renal allografts suffering acute rejection.

Results

Here we observed that in renal allografts undergoing acute rejection, primary cilia were retained, with their length increasing 1 week after transplantation and remaining elevated. We used a mouse model of acute renal injury to demonstrate that elongated renal primary cilia in the injured renal tubule show evidence of smoothened accumulation, a biomarker for activation of hedgehog signalling. We conclude that primary cilium-mediated activation of hedgehog signalling is still possible during the acute phase of renal allograft rejection.

A Sexually Dimorphic Role for STAT3 in Sonic Hedgehog Medulloblastoma

Medulloblastoma is the most common malignant brain tumor in children and represents 20% of all pediatric central nervous system neoplasms. While advances in surgery, radiation and chemotherapy have improved overall survival, the lifelong sequelae of these treatments represent a major health care burden and have led to ongoing efforts to find effective targeted treatments. There is a well-recognized male bias in medulloblastoma diagnosis, although the mechanism remains unknown. Herein, we identify a sex-specific role for the transcription factor Signal Transducer and Activator of Transcription 3 (STAT3) in the Sonic Hedgehog (SHH) medulloblastoma subgroup. Specific deletion of Stat3 from granule cell precursors in a spontaneous mouse model of SHH medulloblastoma completely protects male, but not female mice from tumor initiation. Segregation of SHH medulloblastoma patients into high and low STAT3 expressing cohorts shows that low STAT3 expression correlates with improved overall survival in male patients. We observe sex specific changes in IL-10 and IL-6 expression and show that IL-6 stimulation enhances SHH-mediated gene transcription in a STAT3-dependent manner. Together these data identify STAT3 as a key molecule underpinning the sexual dimorphism in medulloblastoma.

Inhibition of activin signaling in lung adenocarcinoma increases the therapeutic index of platinum chemotherapy

Resistance to platinum chemotherapy is a long-standing problem in the management of lung adenocarcinoma. Using a whole-genome synthetic lethal RNA interference screen, we identified activin signaling as a critical mediator of innate platinum resistance. The transforming growth factor-β (TGFβ) superfamily ligands activin A and growth differentiation factor 11 (GDF11) mediated resistance via their cognate receptors through TGFβ-activated kinase 1 (TAK1), rather than through the SMAD family of transcription factors. Inhibition of activin receptor signaling or blockade of activin A and GDF11 by the endogenous protein follistatin overcame this resistance. Consistent with the role of activin signaling in acute renal injury, both therapeutic interventions attenuated acute cisplatin-induced nephrotoxicity, its major dose-limiting side effect. This cancer-specific enhancement of platinum-induced cell death has the potential to dramatically improve the safety and efficacy of chemotherapy in lung cancer patients.

Genomic stratification and liquid biopsy in a rare adrenocortical carcinoma (ACC) case, with dual lung metastases

Adrenocortical carcinoma is a rare malignancy with a poor prognosis and few treatment options. Molecular characterization of this cancer remains limited. We present a case of an adrenocortical carcinoma (ACC) in a 37-yr-old female, with dual lung metastases identified 1 yr following commencement of adjuvant mitotane therapy. As standard therapeutic regimens are often unsuccessful in ACC, we undertook a comprehensive genomic study into this case to identify treatment options and monitor disease progress. We performed targeted and whole-genome sequencing of germline, primary tumor, and both metastatic tumors from this patient and monitored recurrence over 2 years using liquid biopsy for ctDNA and steroid hormone measurements. Sequencing revealed the primary and metastatic tumors were hyperhaploid, with extensive loss of heterozygosity but few structural rearrangements. Loss-of-function mutations were identified in MSH2, TP53, RB1, and PTEN, resulting in tumors with mismatch repair signatures and microsatellite instability. At the cellular level, tumors were populated by mitochondria-rich oncocytes. Longitudinal ctDNA mutation and hormone profiles were unable to detect micrometastatic disease, consistent with clinical indicators of disease remission. The molecular signatures in our ACC case suggested immunotherapy in the event of disease progression; however, the patient remains free of cancer. The extensive molecular analysis presented here could be applied to other rare and/or poorly stratified cancers to identify novel or repurpose existing therapeutic options, thereby broadly improving diagnoses, treatments, and prognoses.

Targeting promiscuous heterodimerization overcomes innate resistance to ERBB2 dimerization inhibitors in breast cancer

Background

The oncogenic receptor tyrosine kinase (RTK) ERBB2 is known to dimerize with other EGFR family members, particularly ERBB3, through which it potently activates PI3K signalling. Antibody-mediated inhibition of this ERBB2/ERBB3/PI3K axis has been a cornerstone of treatment for ERBB2-amplified breast cancer patients for two decades. However, the lack of response and the rapid onset of relapse in many patients now question the assumption that the ERBB2/ERBB3 heterodimer is the sole relevant effector target of these therapies.

Methods

Through a systematic protein-protein interaction screen, we have identified and validated alternative RTKs that interact with ERBB2. Using quantitative readouts of signalling pathway activation and cell proliferation, we have examined their influence upon the mechanism of trastuzumab- and pertuzumab-mediated inhibition of cell growth in ERBB2-amplified breast cancer cell lines and a patient-derived xenograft model.

Results

We now demonstrate that inactivation of ERBB3/PI3K by these therapeutic antibodies is insufficient to inhibit the growth of ERBB2-amplified breast cancer cells. Instead, we show extensive promiscuity between ERBB2 and an array of RTKs from outside of the EGFR family. Paradoxically, pertuzumab also acts as an artificial ligand to promote ERBB2 activation and ERK signalling, through allosteric activation by a subset of these non-canonical RTKs. However, this unexpected activation mechanism also increases the sensitivity of the receptor network to the ERBB2 kinase inhibitor lapatinib, which in combination with pertuzumab, displays a synergistic effect in single-agent resistant cell lines and PDX models.

Conclusions

The interaction of ERBB2 with a number of non-canonical RTKs activates a compensatory signalling response following treatment with pertuzumab, although a counter-intuitive combination of ERBB2 antibody therapy and a kinase inhibitor can overcome this innate therapeutic resistance.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1127-y) contains supplementary material, which is available to authorized users.

Targeting stromal remodeling and cancer stem cell plasticity overcomes chemoresistance in triple negative breast cancer

The cellular and molecular basis of stromal cell recruitment, activation and crosstalk in carcinomas is poorly understood, limiting the development of targeted anti-stromal therapies. In mouse models of triple negative breast cancer (TNBC), Hedgehog ligand produced by neoplastic cells reprograms cancer-associated fibroblasts (CAFs) to provide a supportive niche for the acquisition of a chemo-resistant, cancer stem cell (CSC) phenotype via FGF5 expression and production of fibrillar collagen. Stromal treatment of patient-derived xenografts with smoothened inhibitors (SMOi) downregulates CSC markers expression and sensitizes tumors to docetaxel, leading to markedly improved survival and reduced metastatic burden. In the phase I clinical trial EDALINE, 3 of 12 patients with metastatic TNBC derived clinical benefit from combination therapy with the SMOi Sonidegib and docetaxel chemotherapy, with one patient experiencing a complete response. These studies identify Hedgehog signaling to CAFs as a novel mediator of CSC plasticity and an exciting new therapeutic target in TNBC.

Targeting stromal remodeling and cancer stem cell plasticity overcomes chemoresistance in triple negative breast cancer

The cellular and molecular basis of stromal cell recruitment, activation and crosstalk in carcinomas is poorly understood, limiting the development of targeted anti-stromal therapies. In mouse models of triple negative breast cancer (TNBC), Hedgehog ligand produced by neoplastic cells reprograms cancer-associated fibroblasts (CAFs) to provide a supportive niche for the acquisition of a chemo-resistant, cancer stem cell (CSC) phenotype via FGF5 expression and production of fibrillar collagen. Stromal treatment of patient-derived xenografts with smoothened inhibitors (SMOi) downregulates CSC markers expression and sensitizes tumors to docetaxel, leading to markedly improved survival and reduced metastatic burden. In the phase I clinical trial EDALINE, 3 of 12 patients with metastatic TNBC derived clinical benefit from combination therapy with the SMOi Sonidegib and docetaxel chemotherapy, with one patient experiencing a complete response. These studies identify Hedgehog signaling to CAFs as a novel mediator of CSC plasticity and an exciting new therapeutic target in TNBC.

Stromal cell recruitment, activation and crosstalk with cancer cells is poorly understood. Here, the authors demonstrate that cancer cell-derived Hedgehog ligand  triggers stromal remodeling that in turn induces a cancer-stem-cell like, drug-resistant phenotype of nearby cancer cells while treatment with smoothened inhibitors reverses these phenotypes.

The tumor suppressor Hic1 maintains chromosomal stability independent of Tp53

Hypermethylated-in-Cancer 1 (Hic1) is a tumor suppressor gene frequently inactivated by epigenetic silencing and loss-of-heterozygosity in a broad range of cancers. Loss of HIC1, a sequence-specific zinc finger transcriptional repressor, results in deregulation of genes that promote a malignant phenotype in a lineage-specific manner. In particular, upregulation of the HIC1 target gene SIRT1, a histone deacetylase, can promote tumor growth by inactivating TP53. An alternate line of evidence suggests that HIC1 can promote the repair of DNA double strand breaks through an interaction with MTA1, a component of the nucleosome remodeling and deacetylase (NuRD) complex. Using a conditional knockout mouse model of tumor initiation, we now show that inactivation of Hic1 results in cell cycle arrest, premature senescence, chromosomal instability and spontaneous transformation in vitro. This phenocopies the effects of deleting Brca1, a component of the homologous recombination DNA repair pathway, in mouse embryonic fibroblasts. These effects did not appear to be mediated by deregulation of Hic1 target gene expression or loss of Tp53 function, and rather support a role for Hic1 in maintaining genome integrity during sustained replicative stress. Loss of Hic1 function also cooperated with activation of oncogenic KRas in the adult airway epithelium of mice, resulting in the formation of highly pleomorphic adenocarcinomas with a micropapillary phenotype in vivo. These results suggest that loss of Hic1 expression in the early stages of tumor formation may contribute to malignant transformation through the acquisition of chromosomal instability.

A phase IIa study of HA-irinotecan, formulation of hyaluronic acid and irinotecan targeting CD44 in extensive-stage small cell lung cancer

Preclinical studies in small cell lung cancer (SCLC) have shown that hyaluronic acid (HA) can be effectively used to deliver chemotherapy and selectively decrease CD44 expressing (stem cell-like) tumour cells. The current study aimed to replicate these findings and obtain data on safety and activity of HA-irinotecan (HA-IR). Eligible patients with extensive stage SCLC were consented. A safety cohort (n = 5) was treated with HA-IR and Carboplatin (C). Subsequently, the patients were randomised 1:1 to receive experimental (HA-IR + C) or standard (IR + C) treatment, to a maximum of 6 cycles. The second line patients were added to the study and treated with open label HA-IR + C. Tumour response was measured after every 2 cycles. Baseline tumour specimens were stained for CD44s and CD44v6 expression. Circulating tumour cells (CTCs) were enumerated before each treatment cycle. Out of 39 patients screened, 34 were evaluable for the study. The median age was 66 (range 39-83). The overall response rates were 69% and 75% for experimental and standard arms respectively. Median progression free survival was 42 and 28 weeks, respectively (p = 0.892). The treatments were well tolerated. The incidence of grade III/IV diarrhea was more common in the standard arm, while anaemia was more common in the experimental arm. IHC analysis suggested that the patients with CD44s positive tumours may gain survival benefit from HA-IR. HA-IR is well tolerated and active in ES-SCLC. The effect of HA-IR on CD44s + cancer stem-like cells provide an early hint towards a potential novel target.

In vivo evidence that RBM5 is a tumour suppressor in the lung

Cigarette smoking is undoubtedly a risk factor for lung cancer. Moreover, smokers with genetic mutations on chromosome 3p21.3, a region frequently deleted in cancer and notably in lung cancer, have a dramatically higher risk of aggressive lung cancer. The RNA binding motif 5 (RBM5) is one of the component genes in the 3p21.3 tumour suppressor region. Studies using human cancer specimens and cell lines suggest a role for RBM5 as a tumour suppressor. Here we demonstrate, for the first time, an in vivo role for RBM5 as a tumour suppressor in the mouse lung. We generated Rbm5 loss-of-function mice and exposed them to a tobacco carcinogen NNK. Upon exposure to NNK, Rbm5 loss-of-function mice developed lung cancer at similar rates to wild type mice. As tumourigenesis progressed, however, reduced Rbm5 expression lead to significantly more aggressive lung cancer i.e. increased adenocarcinoma nodule numbers and tumour size. Our data provide in vivo evidence that reduced RBM5 function, as occurs in a large number of patients, coupled with exposure to tobacco carcinogens is a risk factor for an aggressive lung cancer phenotype. These data suggest that RBM5 loss-of-function likely underpins at least part of the pro-tumourigenic consequences of 3p21.3 deletion in humans.

Mechanisms regulating phosphatase specificity and the removal of individual phosphorylation sites during mitotic exit

Entry into mitosis is driven by the activity of kinases, which phosphorylate over 7000 proteins on multiple sites. For cells to exit mitosis and segregate their genome correctly, these phosphorylations must be removed in a specific temporal order. This raises a critical and important question: how are specific phosphorylation sites on an individual protein removed? Traditionally, the temporal order of dephosphorylation was attributed to decreasing kinase activity. However, recent evidence in human cells has identified unique patterns of dephosphorylation during mammalian mitotic exit that cannot be fully explained by the loss of kinase activity. This suggests that specificity is determined in part by phosphatases. In this review, we explore how the physicochemical properties of an individual phosphosite and its surrounding amino acids can affect interactions with a phosphatase. These positive and negative interactions in turn help determine the specific pattern of dephosphorylation required for correct mitotic exit.

Abstract 3170: MCAM modulates small cell lung cancer chemoresistance via PI3k/Akt/Sox2 signaling pathway

Despite favorable responses to initial therapy SCLC relapse occurs within a year exhibiting a multidrug resistant phenotype. Due to limited accessibility of patient tissues for research purpose, SCLC patient derived xenografts (PDXs) have provided the best opportunity to address this limitation. We sought to identify novel mechanisms involved in SCLC chemoresistance. Through in-depth proteomic profiling, we identified MCAM as a markedly upregulated surface receptor in chemoresistant SCLC cell lines that exhibited a mesenchymal phenotype and in chemoresistant PDXs compared to matched treatment-naïve tumors. MCAM is a cell membrane protein whose expression has been implicated in multiple human cancers. MCAM expression is also detected in lung adenocarcinoma; however, its expression and role in SCLC is still not been explored. MCAM knockdown in chemoresistant cells reduced cell proliferation and decreased the IC50 inhibitory concentration of chemotherapeutic drugs. MCAM was found to modulate sensitivity of SCLC cells to chemotherapeutic drugs through up-regulation of MRP1/ABCC1 expression and of the PI3K/AKT pathway in a SOX2 dependent manner. Metabolomic profiling revealed that MCAM can modulate glutamic acid and lactate production in chemoresistant cells with a distinct metabolic phenotype sustaining low oxidative phosphorylation. MCAM may serve as a novel therapeutic target to overcome chemoresistance in SCLC.

Citation Format: Satyendra C. Tripathi, Johannes F. Fahrmann, Muge Celiktas, Mitzi Aguilar, Kieren D. Marini, Mohit K. Jolly, Hiroyuki Katayama, Hong Wang, Eunice N. Murage, Jennifer B. Dennison, D. Neil Watkins, Herbert Levine, Edwin J. Ostrin, Ayumu Taguchi, Samir M. Hanash. MCAM modulates small cell lung cancer chemoresistance via PI3k/Akt/Sox2 signaling pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3170. doi:10.1158/1538-7445.AM2017-3170

Abstract 3360: Targeted catalytic inhibition of EZH2 synergizes with low-dose HDACi in malignant rhabdoid tumors

Malignant Rhabdoid Tumor (MRT) is a rare pediatric cancer of the kidney and CNS that is resistant to current treatment protocols. MRT is genetically characterized by homozygous inactivation of SMARCB1, a critical subunit of the SWI/SNF chromatin-remodeling complex. Next-generation sequencing data suggests that inactivation of SMARCB1 is the primary driver mutation, implicating epigenetic deregulation in the pathogenesis of MRT. Recently, we showed that sustained treatment of MRT cell lines with low-dose Panobinostat (LBH589), inhibited tumor growth by driving multi-lineage differentiation in vitro and in vivo. Furthermore, re-expression of physiological levels of SMARCB1 in G401 MRT cells phenocopied the low-dose LBH589 treatment and led to growth inhibition, senescence and terminal differentiation in vitro and in vivo. Enhancer of Zeste homolog 2 (EZH2), a core subunit of the Polycomb Repressive Complex 2 (PRC2), confers transcriptional silencing via the addition of methyl groups to Lysine 27 of Histone 3 (H3K27me3), and is a transcriptional target of SMARCB1. EZH2 expression and H3K27me3 were drastically reduced following sustained low-dose LBH589 treatment and re-expression of SMARCB1 in G401 MRT cells. Sustained siRNA knockdown of EZH2 in G401 cells resulted in reduced cell growth and changes in mRNA expression similar to those observed following low-dose LBH589 treatment and SMARCB1 re-expression. Treatment of MRT cells with the EZH2-catalytic domain inhibitor, GSK-126, had no effect on EZH2 expression and only partially reduced H3K27me3 and cell growth at doses 1nM-10μM suggesting important non-catalytic EZH2 function. However, MRT cells treated in combination with low-dose LBH589 and GSK-126, lost EZH2 and H3K27me3 expression and exhibited significantly reduced cell growth in vitro compared to single agent controls, revealing a synergistic relationship. Similar effects were observed in an in vivo xenograft model, with low-dose LBH589 and GSK-126 treatment leading to a marked reduction in tumor growth, not observed with single agent treatment. This data suggests EZH2 is an important mediator of MRT proliferation and differentiation and provides evidence for dual therapeutic targeting of EZH2 with low-dose HDACi in MRT.

Citation Format: Dean Popovski, Elizabeth M. Algar, Catherine R. Cochrane, Anette Szczepny, W. Samantha Jayasekara, David M. Ashley, Peter Downie, D. Neil Watkins, Jason E. Cain. Targeted catalytic inhibition of EZH2 synergizes with low-dose HDACi in malignant rhabdoid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3360. doi:10.1158/1538-7445.AM2017-3360

A compartmentalized phosphoinositide signaling axis at cilia is regulated by INPP5E to maintain cilia and promote Sonic Hedgehog medulloblastoma

Sonic Hedgehog (SHH) signaling at primary cilia drives the proliferation and progression of a subset of medulloblastomas, the most common malignant paediatric brain tumor. Severe side effects associated with conventional treatments and resistance to targeted therapies has led to the need for new strategies. SHH signaling is dependent on primary cilia for signal transduction suggesting the potential for cilia destabilizing mechanisms as a therapeutic target. INPP5E is an inositol polyphosphate 5-phosphatase that hydrolyses PtdIns(4,5)P₂ and more potently, the phosphoinositide (PI) 3-kinase product PtdIns(3,4,5)P₃. INPP5E promotes SHH signaling during embryonic development via PtdIns(4,5)P₂ hydrolysis at cilia, that in turn regulates the cilia recruitment of the SHH suppressor GPR161. However, the role INPP5E plays in cancer is unknown and the contribution of PI3-kinase signaling to cilia function is little characterized. Here, we reveal INPP5E promotes SHH signaling in SHH medulloblastoma by negatively regulating a cilia-compartmentalized PI3-kinase signaling axis that maintains primary cilia on tumor cells. Conditional deletion of Inpp5e in a murine model of constitutively active Smoothened-driven medulloblastoma slowed tumor progression, suppressed cell proliferation, reduced SHH signaling and promoted tumor cell cilia loss. PtdIns(3,4,5)P₃, its effector pAKT and the target pGSK3β, which when non-phosphorylated promotes cilia assembly/stability, localized to tumor cell cilia. The number of PtdIns(3,4,5)P₃/pAKT/pGSK3β-positive cilia was increased in cultured Inpp5e-null tumor cells relative to controls. PI3-kinase inhibition or expression of wild-type, but not catalytically inactive HA-INPP5E partially rescued cilia loss in Inpp5e-null tumor cells in vitro. INPP5E mRNA and copy number were reduced in human SHH medulloblastoma compared to other molecular subtypes and consistent with the murine model, reduced INPP5E was associated with improved overall survival. Therefore our study identifies a compartmentalized PtdIns(3,4,5)P₃/AKT/GSK3β signaling axis at cilia in SHH-dependent medulloblastoma that is regulated by INPP5E to maintain tumor cell cilia, promote SHH signaling and thereby medulloblastoma progression.

MCAM Mediates Chemoresistance in Small-Cell Lung Cancer via the PI3K/AKT/SOX2 Signaling Pathway

Despite favorable responses to initial therapy, small-cell lung cancer (SCLC) relapse occurs within a year and exhibits resistance to multiple drugs. Because of limited accessibility of patient tissues for research purposes, SCLC patient-derived xenografts (PDX) have provided the best opportunity to address this limitation. Here, we sought to identify novel mechanisms involved in SCLC chemoresistance. Through in-depth proteomic profiling, we identified MCAM as a markedly upregulated surface receptor in chemoresistant SCLC cell lines and in chemoresistant PDX compared with matched treatment-naïve tumors. MCAM depletion in chemoresistant cells reduced cell proliferation and reduced the IC₅₀ inhibitory concentration of chemotherapeutic drugs in vitro This MCAM-mediated sensitization to chemotherapy occurred via SOX2-dependent upregulation of mitochondrial 37S ribosomal protein 1/ATP-binding cassette subfamily C member 1 (MRP1/ABCC1) and the PI3/AKT pathway. Metabolomic profiling revealed that MCAM modulated lactate production in chemoresistant cells that exhibit a distinct metabolic phenotype characterized by low oxidative phosphorylation. Our results suggest that MCAM may serve as a novel therapeutic target to overcome chemoresistance in SCLC. Cancer Res; 77(16); 4414-25. ©2017 AACR.

The role of canonical and non-canonical Hedgehog signaling in tumor progression in a mouse model of small cell lung cancer

Hedgehog (Hh) signaling regulates cell fate and self-renewal in development and cancer. Canonical Hh signaling is mediated by Hh ligand binding to the receptor Patched (Ptch), which in turn activates Gli-mediated transcription through Smoothened (Smo), the molecular target of the Hh pathway inhibitors used as cancer therapeutics. Small cell lung cancer (SCLC) is a common, aggressive malignancy with universally poor prognosis. Although preclinical studies have shown that Hh inhibitors block the self-renewal capacity of SCLC cells, the lack of activating pathway mutations have cast doubt over the significance of these observations. In particular, the existence of autocrine, ligand-dependent Hh signaling in SCLC has been disputed. In a conditional Tp53;Rb1 mutant mouse model of SCLC, we now demonstrate a requirement for the Hh ligand Sonic Hedgehog (Shh) for the progression of SCLC. Conversely, we show that conditional Shh overexpression activates canonical Hh signaling in SCLC cells, and markedly accelerates tumor progression. When compared to mouse SCLC tumors expressing an activating, ligand-independent Smo mutant, tumors overexpressing Shh exhibited marked chromosomal instability and Smoothened-independent upregulation of Cyclin B1, a putative non-canonical arm of the Hh pathway. In turn, we show that overexpression of Cyclin B1 induces chromosomal instability in mouse embryonic fibroblasts lacking both Tp53 and Rb1. These results provide strong support for an autocrine, ligand-dependent model of Hh signaling in SCLC pathogenesis, and reveal a novel role for non-canonical Hh signaling through the induction of chromosomal instability.

Widespread GLI expression but limited canonical hedgehog signaling restricted to the ductular reaction in human chronic liver disease

Canonical Hedgehog (Hh) signaling in vertebrate cells occurs following Smoothened activation/translocation into the primary cilia (Pc), followed by a GLI transcriptional response. Nonetheless, GLI activation can occur independently of the canonical Hh pathway. Using a murine model of liver injury, we previously identified the importance of canonical Hh signaling within the Pc⁺ liver progenitor cell (LPC) population and noted that SMO-independent, GLI-mediated signals were important in multiple Pc^-ve GLI2⁺ intrahepatic populations. This study extends these observations to human liver tissue, and analyses the effect of GLI inhibition on LPC viability/gene expression. Human donor and cirrhotic liver tissue specimens were evaluated for SHH, GLI2 and Pc expression using immunofluorescence and qRT-PCR. Changes to viability and gene expression in LPCs in vitro were assessed following GLI inhibition. Identification of Pc (as a marker of canonical Hh signaling) in human cirrhosis was predominantly confined to the ductular reaction and LPCs. In contrast, GLI2 was expressed in multiple cell populations including Pc^-ve endothelium, hepatocytes, and leukocytes. HSCs/myofibroblasts (>99%) expressed GLI2, with only 1.92% displaying Pc. In vitro GLI signals maintained proliferation/viability within LPCs and GLI inhibition affected the expression of genes related to stemness, hepatocyte/biliary differentiation and Hh/Wnt signaling. At least two mechanisms of GLI signaling (Pc/SMO-dependent and Pc/SMO-independent) mediate chronic liver disease pathogenesis. This may have significant ramifications for the choice of Hh inhibitor (anti-SMO or anti-GLI) suitable for clinical trials. We also postulate GLI delivers a pro-survival signal to LPCs whilst maintaining stemness.

MCL-1 inhibition provides a new way to suppress breast cancer metastasis and increase sensitivity to dasatinib

BACKGROUND

Metastatic disease is largely resistant to therapy and accounts for almost all cancer deaths. Myeloid cell leukemia-1 (MCL-1) is an important regulator of cell survival and chemo-resistance in a wide range of malignancies, and thus its inhibition may prove to be therapeutically useful.

METHODS

To examine whether targeting MCL-1 may provide an effective treatment for breast cancer, we constructed inducible models of BIMs2A expression (a specific MCL-1 inhibitor) in MDA-MB-468 (MDA-MB-468-2A) and MDA-MB-231 (MDA-MB-231-2A) cells.

RESULTS

MCL-1 inhibition caused apoptosis of basal-like MDA-MB-468-2A cells grown as monolayers, and sensitized them to the BCL-2/BCL-XL inhibitor ABT-263, demonstrating that MCL-1 regulated cell survival. In MDA-MB-231-2A cells, grown in an organotypic model, induction of BIMs2A produced an almost complete suppression of invasion. Apoptosis was induced in such a small proportion of these cells that it could not account for the large decrease in invasion, suggesting that MCL-1 was operating via a previously undetected mechanism. MCL-1 antagonism also suppressed local invasion and distant metastasis to the lung in mouse mammary intraductal xenografts. Kinomic profiling revealed that MCL-1 antagonism modulated Src family kinases and their targets, which suggested that MCL-1 might act as an upstream modulator of invasion via this pathway. Inhibition of MCL-1 in combination with dasatinib suppressed invasion in 3D models of invasion and inhibited the establishment of tumors in vivo.

CONCLUSION

These data provide the first evidence that MCL-1 drives breast cancer cell invasion and suggests that MCL-1 antagonists could be used alone or in combination with drugs targeting Src kinases such as dasatinib to suppress metastasis.

Calretinin but not caveolin-1 correlates with tumour histology and survival in malignant mesothelioma

Malignant mesothelioma (MM) continues to be a disease with poor prognosis and limited treatment options. Calretinin and caveolin-1 expression by tumour in MM have recently been described to be associated with tumour histology, differentiation and consequently survival. In a large, well annotated cohort, we studied both of these biomarkers and explored their association with clinicopathological parameters and survival. A retrospective search of patients with MM who underwent surgery at the Austin Hospital in Melbourne, Australia, was conducted. Clinical history and outcome data were retrieved from patient records. Tissue microarrays (TMAs) were constructed and stained for calretinin and caveolin-1. 'H scores' were derived, taking intensity and distribution of staining, and the cohort was dichotomised using median values for both markers. In the 329 patients evaluated, median age was 67 years. Males outnumbered females by 5:1. Epithelioid histology 202/319 (62.9%) was the most common, followed by biphasic 72/319 (21.8%) and sarcomatoid 45/319 (13.6%); histology could not be confirmed in 10 patients. Calretinin expression was detected in 246 of the 324 (76%) evaluable patients and high expression was associated with epithelioid histology (p < 0.0001). Caveolin-1 was expressed in 298 (94%) of 317 evaluable patients which was much higher compared to its expression in a cohort of lung adenocarcinomas (8/58, 13.7%). However, no association with histology was found (p = 0.409). When taken as a continuous variable, calretinin expression was found to be an independent predictor of survival, alongside histology, neutrophil-lymphocyte ratio, weight loss and stage. No prognostic value was demonstrable for caveolin-1 expression and calretinin/caveolin-1 ratio. There was no relationship between calretinin and caveolin-1 expression. In MM, increased calretinin expression is associated with epithelioid histology and better survival. Caveolin-1 is a sensitive MM marker and is expressed in a high proportion of cases but lacks association with histology and survival.

Low-Dose Histone Deacetylase Inhibitor Treatment Leads to Tumor Growth Arrest and Multi-Lineage Differentiation of Malignant Rhabdoid Tumors

PURPOSE

Malignant rhabdoid tumor (MRT) and atypical teratoid rhabdoid tumors (ATRT) are rare aggressive undifferentiated tumors primarily affecting the kidney and CNS of infants and young children. MRT are almost exclusively characterized by homozygous deletion or inactivation of the chromatin remodeling gene SMARCB1 SMARCB1 protein loss leads to direct impairment of chromatin remodeling and we have previously reported a role for this protein in histone acetylation. This provided the rationale for investigating the therapeutic potential of histone deactylase inhibitors (HDACi) in MRT.

EXPERIMENTAL DESIGN

Whereas previously HDACis have been used at doses and schedules that induce cytotoxicity, in the current studies we have tested the hypothesis, both in vitro and in vivo, that sustained treatment of human MRT with low-dose HDACi can lead to sustained cell growth arrest and differentiation.

RESULTS

Sustained low-dose panobinostat (LBH589) treatment led to changes in cellular morphology associated with a marked increase in the induction of neural, renal, and osteoblast differentiation pathways. Genome-wide transcriptional profiling highlighted differential gene expression supporting multilineage differentiation. Using mouse xenograft models, sustained low-dose LBH589 treatment caused tumor growth arrest associated with tumor calcification detectable by X-ray imaging. Histological analysis of LBH589-treated tumors revealed significant regions of ossification, confirmed by Alizarin Red staining. Immunohistochemical analysis showed increased TUJ1 and PAX2 staining suggestive of neuronal and renal differentiation, respectively.

CONCLUSIONS

Low-dose HDACi treatment can terminally differentiate MRT tumor cells and reduce their ability to self-renew. The use of low-dose HDACi as a novel therapeutic approach warrants further investigation. Clin Cancer Res; 22(14); 3560-70. ©2016 AACR.

PP1 initiates the dephosphorylation of MASTL, triggering mitotic exit and bistability in human cells

Entry into mitosis is driven by the phosphorylation of thousands of substrates, under the master control of Cdk1. During entry into mitosis, Cdk1, in collaboration with MASTL kinase, represses the activity of the major mitotic protein phosphatases, PP1 and PP2A, thereby ensuring mitotic substrates remain phosphorylated. For cells to complete and exit mitosis, these phosphorylation events must be removed, and hence, phosphatase activity must be reactivated. This reactivation of phosphatase activity presumably requires the inhibition of MASTL; however, it is not currently understood what deactivates MASTL and how this is achieved. In this study, we identified that PP1 is associated with, and capable of partially dephosphorylating and deactivating, MASTL during mitotic exit. Using mathematical modelling, we were able to confirm that deactivation of MASTL is essential for mitotic exit. Furthermore, small decreases in Cdk1 activity during metaphase are sufficient to initiate the reactivation of PP1, which in turn partially deactivates MASTL to release inhibition of PP2A and, hence, create a feedback loop. This feedback loop drives complete deactivation of MASTL, ensuring a strong switch-like activation of phosphatase activity during mitotic exit.

The mouse endometrium contains epithelial, endothelial and leucocyte populations expressing the stem cell marker telomerase reverse transcriptase

STUDY HYPOTHESIS

The mouse endometrium harbours stem/progenitor cells that express the stem cell marker mouse telomerase reverse transcriptase (mTert).

STUDY FINDING

We used a mouse carrying a transgenic reporter for mTert promoter activity to identify rare endometrial populations of epithelial and endothelial cells that express mTert.

WHAT IS KNOWN ALREADY

Stem/progenitor cells are hypothesized to be responsible for the remarkable regenerative capacity of the endometrium, but the lack of convenient endometrial stem/progenitor markers in the mouse has hampered investigations into the identity of these cells.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

A mouse containing a green fluorescent protein (GFP) reporter under the control of the telomerase reverse transcriptase promoter (mTert-GFP) was used to identify potential stem/progenitor cells in the endometrium. mTert promoter activity was determined using fluorescence microscopy and flow cytometry to identify GFP(+) cells. GFP(+) cells were examined for epithelial, stromal, endothelial, leucocyte and proliferation markers and bromodeoxyuridine retention to determine their identity. The endometrium of ovariectomized mice was compared to that of intact cycling mice to establish the role of ovarian hormones in maintaining mTert-expressing cells.

MAIN RESULTS AND THE ROLE OF CHANCE

We found that mTert-GFP is expressed by rare luminal and glandular epithelial cells (0.3% of epithelial cells by flow cytometry), rare CD45(-) cells in the stromal compartment (0.028 ± 0.010% of stromal cells by microscopy) and many CD45(+) leucocytes. Ovariectomy resulted in significant decrease of mTert-GFP(+) epithelial cells (P = 0.029 for luminal epithelium; P = 0.034 for glandular epithelium) and a decrease in the percentage of mTert-GFP(+) CD45(+) leucocytes in the stromal compartment (P = 0.015). However, CD45(-) mTert-GFP(+) cells in the stromal compartment were maintained in ovariectomized mice. This population is enriched for cells bearing the endothelial marker CD31 (10.3% of CD90(-) CD45(-) and 97.8% CD90(+) CD45(-) by flow cytometry). CD45(-) mTert-GFP(+) cells also immunostained for the endothelial marker von Willebrand factor. These results suggest that the endometrial epithelium and vasculature are foci of stem/progenitor activity and provide a system to investigate molecular mechanisms involved in endometrial regeneration and repair.

LIMITATIONS, REASONS FOR CAUTION

The stem/progenitor activity of endometrial mTert-GFP(+) cells needs to be experimentally verified.

WIDER IMPLICATIONS OF THE FINDINGS

The identification and characterization of mTert-expressing progenitor cells in the mouse will facilitate the identification of equivalent populations in the human endometrium that are likely to be involved in endometrial function, fertility and disease.

LARGE-SCALE DATA

Not applicable.

STUDY FUNDING AND COMPETING INTERESTS

This study was funded by National Health and Medical Research Council (NHMRC) of Australia grants (1085435, C.E.G., J.A.D.), 1021127 (C.E.G.), NHMRC Senior Research Fellowship (1042298, C.E.G.), the Victorian Infrastructure Support Program, U.S. National Institutes of Health grant R01 DK084056 (D.T.B.) and the Harvard Stem Cell Institute (D.T.B.). The authors have no conflicts of interest to declare.

Dataset from the global phosphoproteomic mapping of early mitotic exit in human cells

The presence or absence of a phosphorylation on a substrate at any particular point in time is a functional readout of the balance in activity between the regulatory kinase and the counteracting phosphatase. Understanding how stable or short-lived a phosphorylation site is required for fully appreciating the biological consequences of the phosphorylation. Our current understanding of kinases and their substrates is well established; however, the role phosphatases play is less understood. Therefore, we utilized a phosphatase dependent model of mitotic exit to identify potential substrates that are preferentially dephosphorylated. Using this method, we identified >16,000 phosphosites on >3300 unique proteins, and quantified the temporal phosphorylation changes that occur during early mitotic exit (McCloy et al., 2015 [1]). Furthermore, we annotated the majority of these phosphorylation sites with a high confidence upstream kinase using published, motif and prediction based methods. The results from this study have been deposited into the ProteomeXchange repository with identifier PXD001559. Here we provide additional analysis of this dataset; for each of the major mitotic kinases we identified motifs that correlated strongly with phosphorylation status. These motifs could be used to predict the stability of phosphorylated residues in proteins of interest, and help infer potential functional roles for uncharacterized phosphorylations. In addition, we provide validation at the single cell level that serine residues phosphorylated by Cdk are stable during phosphatase dependent mitotic exit. In summary, this unique dataset contains information on the temporal mitotic stability of thousands of phosphorylation sites regulated by dozens of kinases, and information on the potential preference that phosphatases have at both the protein and individual phosphosite level. The compellation of this data provides an invaluable resource for the wider research community.

Hedgehog Signaling in the Maintenance of Cancer Stem Cells

Cancer stem cells (CSCs) represent a rare population of cells with the capacity to self-renew and give rise to heterogeneous cell lineages within a tumour. Whilst the mechanisms underlying the regulation of CSCs are poorly defined, key developmental signaling pathways required for normal stem and progenitor functions have been strongly implicated. Hedgehog (Hh) signaling is an evolutionarily-conserved pathway essential for self-renewal and cell fate determination. Aberrant Hh signaling is associated with the development and progression of various types of cancer and is implicated in multiple aspects of tumourigenesis, including the maintenance of CSCs. Here, we discuss the mounting evidence suggestive of Hh-driven CSCs in the context of haematological malignancies and solid tumours and the novel strategies that hold the potential to block many aspects of the transformation attributed to the CSC phenotype, including chemotherapeutic resistance, relapse and metastasis.

Global Phosphoproteomic Mapping of Early Mitotic Exit in Human Cells Identifies Novel Substrate Dephosphorylation Motifs

Entry into mitosis is driven by the coordinated phosphorylation of thousands of proteins. For the cell to complete mitosis and divide into two identical daughter cells it must regulate dephosphorylation of these proteins in a highly ordered, temporal manner. There is currently a lack of a complete understanding of the phosphorylation changes that occur during the initial stages of mitotic exit in human cells. Therefore, we performed a large unbiased, global analysis to map the very first dephosphorylation events that occur as cells exit mitosis. We identified and quantified the modification of >16,000 phosphosites on >3300 unique proteins during early mitotic exit, providing up to eightfold greater resolution than previous studies. The data have been deposited to the ProteomeXchange with identifier PXD001559. Only a small fraction (∼ 10%) of phosphorylation sites were dephosphorylated during early mitotic exit and these occurred on proteins involved in critical early exit events, including organization of the mitotic spindle, the spindle assembly checkpoint, and reformation of the nuclear envelope. Surprisingly this enrichment was observed across all kinase consensus motifs, indicating that it is independent of the upstream phosphorylating kinase. Therefore, dephosphorylation of these sites is likely determined by the specificity of phosphatase/s rather than the activity of kinase/s. Dephosphorylation was significantly affected by the amino acids at and surrounding the phosphorylation site, with several unique evolutionarily conserved amino acids correlating strongly with phosphorylation status. These data provide a potential mechanism for the specificity of phosphatases, and how they co-ordinate the ordered events of mitotic exit. In summary, our results provide a global overview of the phosphorylation changes that occur during the very first stages of mitotic exit, providing novel mechanistic insight into how phosphatase/s specifically regulate this critical transition.

Genomic characterisation of small cell lung cancer patient-derived xenografts generated from endobronchial ultrasound-guided transbronchial needle aspiration specimens

Patient-derived xenograft (PDX) models generated from surgical specimens are gaining popularity as preclinical models of cancer. However, establishment of PDX lines from small cell lung cancer (SCLC) patients is difficult due to very limited amount of available biopsy material. We asked whether SCLC cells obtained from endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) could generate PDX lines that maintained the phenotypic and genetic characteristics of the primary tumor. Following successful EBUS-TBNA sampling for diagnostic purposes, we obtained an extra sample for cytologic analysis and implantation into the flanks of immunodeficient mice. Animals were monitored for engraftment for up to 6 months. Histopathologic and immunohistochemical analysis, and targeted next-generation re-sequencing, were then performed in both the primary sample and the derivative PDX line. A total of 12 patients were enrolled in the study. EBUS-TBNA aspirates yielded large numbers of viable tumor cells sufficient to inject between 18,750 and 1,487,000 cells per flank, and to yield microgram quantities of high-quality DNA. Of these, samples from 10 patients generated xenografts (engraftment rate 83%) with a mean latency of 104 days (range 63–188). All but one maintained a typical SCLC phenotype that closely matched the original sample. Identical mutations that are characteristic of SCLC were identified in both the primary sample and xenograft line. EBUS-TBNA has the potential to be a powerful tool in the development of new targeting strategies for SCLC patients by providing large numbers of viable tumor cells suitable for both xenografting and complex genomic analysis.

Hedgehog signaling regulates FOXA2 in esophageal embryogenesis and Barrett's metaplasia

Metaplasia can result when injury reactivates latent developmental signaling pathways that determine cell phenotype. Barrett's esophagus is a squamous-to-columnar epithelial metaplasia caused by reflux esophagitis. Hedgehog (Hh) signaling is active in columnar-lined, embryonic esophagus and inactive in squamous-lined, adult esophagus. We showed previously that Hh signaling is reactivated in Barrett's metaplasia and overexpression of Sonic hedgehog (SHH) in mouse esophageal squamous epithelium leads to a columnar phenotype. Here, our objective was to identify Hh target genes involved in Barrett's pathogenesis. By microarray analysis, we found that the transcription factor Foxa2 is more highly expressed in murine embryonic esophagus compared with postnatal esophagus. Conditional activation of Shh in mouse esophageal epithelium induced FOXA2, while FOXA2 expression was reduced in Shh knockout embryos, establishing Foxa2 as an esophageal Hh target gene. Evaluation of patient samples revealed FOXA2 expression in Barrett's metaplasia, dysplasia, and adenocarcinoma but not in esophageal squamous epithelium or squamous cell carcinoma. In esophageal squamous cell lines, Hh signaling upregulated FOXA2, which induced expression of MUC2, an intestinal mucin found in Barrett's esophagus, and the MUC2-processing protein AGR2. Together, these data indicate that Hh signaling induces expression of genes that determine an intestinal phenotype in esophageal squamous epithelial cells and may contribute to the development of Barrett's metaplasia.

Seminoma and embryonal carcinoma footprints identified by analysis of integrated genome-wide epigenetic and expression profiles of germ cell cancer cell lines

Background

Originating from Primordial Germ Cells/gonocytes and developing via a precursor lesion called Carcinoma In Situ (CIS), Germ Cell Cancers (GCC) are the most common cancer in young men, subdivided in seminoma (SE) and non-seminoma (NS). During physiological germ cell formation/maturation, epigenetic processes guard homeostasis by regulating the accessibility of the DNA to facilitate transcription. Epigenetic deregulation through genetic and environmental parameters (i.e. genvironment) could disrupt embryonic germ cell development, resulting in delayed or blocked maturation. This potentially facilitates the formation of CIS and progression to invasive GCC. Therefore, determining the epigenetic and functional genomic landscape in GCC cell lines could provide insight into the pathophysiology and etiology of GCC and provide guidance for targeted functional experiments.

Results

This study aims at identifying epigenetic footprints in SE and EC cell lines in genome-wide profiles by studying the interaction between gene expression, DNA CpG methylation and histone modifications, and their function in the pathophysiology and etiology of GCC. Two well characterized GCC-derived cell lines were compared, one representative for SE (TCam-2) and the other for EC (NCCIT). Data were acquired using the Illumina HumanHT-12-v4 (gene expression) and HumanMethylation450 BeadChip (methylation) microarrays as well as ChIP-sequencing (activating histone modifications (H3K4me3, H3K27ac)). Results indicate known germ cell markers not only to be differentiating between SE and NS at the expression level, but also in the epigenetic landscape.

Conclusion

The overall similarity between TCam-2/NCCIT support an erased embryonic germ cell arrested in early gonadal development as common cell of origin although the exact developmental stage from which the tumor cells are derived might differ. Indeed, subtle difference in the (integrated) epigenetic and expression profiles indicate TCam-2 to exhibit a more germ cell-like profile, whereas NCCIT shows a more pluripotent phenotype. The results provide insight into the functional genome in GCC cell lines.

Changes in aldehyde dehydrogenase-1 expression during neoadjuvant chemotherapy predict outcome in locally advanced breast cancer

INTRODUCTION

Although neoadjuvant chemotherapy (NAC) for locally advanced breast cancer can improve operability and local disease control, there is a lack of reliable biomarkers that predict response to chemotherapy or long-term survival. Since expression of aldehyde dehydrogenase-1 (ALDH1) is associated with the stem-like properties of self-renewal and innate chemoresistance in breast cancer, we asked whether expression in serial tumor samples treated with NAC could identify women more likely to benefit from this therapy.

METHODS

Women with locally advanced breast cancer were randomly assigned to receive four cycles of anthracycline-based chemotherapy, followed by four cycles of taxane therapy (Arm A), or the same regimen in reverse order (Arm B). Tumor specimens were collected at baseline, after four cycles, and then at surgical resection. ALDH1 expression was determined by immunohistochemistry and correlated with tumor response using Fisher's exact test while Kaplan-Meier method was used to calculate survival.

RESULTS

A hundred and nineteen women were enrolled into the study. Fifty seven (48%) were randomized to Arm A and 62 (52%) to Arm B. Most of the women (90%) had ductal carcinoma and 10% had lobular carcinoma. Of these, 26 (22%) achieved a pathological complete response (pCR) after NAC. There was no correlation between baseline ALDH1 expression and tumor grade, stage, hormone receptor, human epidermal growth factor receptor 2 (HER2) status and Ki67 index. ALDH1 negativity at baseline was significantly associated with pCR (P = 0.004). The presence of ALDH1(+) cells in the residual tumor cells in non-responding women was strongly predictive of worse overall survival (P = 0.024). Moreover, serial analysis of specimens from non-responders showed a marked increase in tumor-specific ALDH1 expression (P = 0.028). Overall, there was no survival difference according to the chemotherapy sequence. However, poorly responding tumours from women receiving docetaxel chemotherapy showed an unexpected significant increase in ALDH1 expression.

CONCLUSIONS

ALDH1 expression is a useful predictor of chemoresistance. The up-regulation of ALDH1 after NAC predicts poor survival in locally advanced breast cancer. Although the chemotherapy sequence had no effect on overall prognosis, our results suggest that anthracycline-based chemotherapy may be more effective at targeting ALDH1(+) breast cancer cells.

TRIAL REGISTRATION

ACTRN12605000588695.

Interaction of smoothened with integrin-linked kinase in primary cilia mediates Hedgehog signalling

Here we report that ILK localizes in the mouse primary cilium, a sensory organelle required for signalling by the Hedgehog (Hh) pathway. Genetic or pharmacological inhibition of ILK blocks ciliary accumulation of the Hh pathway effector smoothened (Smo) and suppresses the induction of Gli transcription factor mRNAs by SHh. Conditional deletion of ILK or Smo also inhibits SHh-driven activation of Gli2 in the embryonic mouse cerebellum. ILK regulation of Hh signalling probably requires the physical interaction of ILK and Smo in the cilium, and we also show selective cilia-associated interaction of ILK with β-arrestin, a known mediator of Smo-dependent signalling.

The prognostic significance of aldehyde dehydrogenase 1A1 (ALDH1A1) and CD133 expression in early stage non-small cell lung cancer

BACKGROUND

Expression of aldehyde dehydrogenase 1A1 (ALDH1A1) and CD133 has been functionally associated with a stem cell phenotype in normal and malignant cells. The prevalence of such cells in solid tumours should therefore correlate with recurrence and/or metastasis following definitive surgical resection. The aim of this study was to evaluate the prognostic significance of ALDH1A1 and CD133 in surgically resected, early stage non-small cell lung cancer (NSCLC).

METHODS

A retrospective analysis of ALDH1A1 and CD133 expression in 205 patients with pathologic stage I NSCLC was performed using immunohistochemistry. The association between the expression of both markers and survival was determined.

RESULTS

We identified 62 relapses and 58 cancer-related deaths in 144 stage 1A and 61 stage 1B patients, analysed at a median of 5-years follow-up. Overexpression of ALDH1A1 and CD133, detected in 68.7% and 50.7% of primary tumours, respectively, was an independent prognostic indicator for overall survival by multivariable Cox proportional hazard model (p=0.017 and 0.039, respectively). Overexpression of ALDH1A1, but not of CD133, predicted poor recurrence-free survival (p=0.025). When categorised into three groups according to expression of ALDH1A1/CD133, patients with overexpression of both ALDH1A1 and CD133 belonged to the group with the shortest recurrence-free and overall survival (p=0.015 and 0.017, respectively).

CONCLUSIONS

Expression of ALDH1A1 and CD133, and coexpression of ALDH1A1 and CD133, is strongly associated with poor survival in early-stage NSCLC following surgical resection. These data are consistent with the hypothesis that expression of stem cell markers correlates with recurrence as an indirect measure of self-renewal capacity.

Cancer stem cells in lung cancer: Evidence and controversies

The cancer stem cell (CSC) 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. CSC 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 CSC have been identified, including CD133 and CD44. In addition, expression and/or activity of the cytoplasmic enzyme aldehyde dehydrogenase 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 CSC in the context of the experimental and clinical evidence and discuss some ongoing controversies regarding this model.

Mutational analysis of hedgehog signaling pathway genes in human malignant mesothelioma

BACKGROUND

The Hedgehog (HH) signaling pathway is critical for embryonic development and adult homeostasis. Recent studies have identified regulatory roles for this pathway in certain cancers with mutations in the HH pathway genes. The extent to which mutations of the HH pathway genes are involved in the pathogenesis of malignant mesothelioma (MMe) is unknown.

METHODOLOGY/PRINCIPAL FINDINGS

Real-time PCR analysis of HH pathway genes PTCH1, GLI1 and GLI2 were performed on 7 human MMe cell lines. Exon sequencing of 13 HH pathway genes was also performed in cell lines and human MMe tumors. In silico programs were used to predict the likelihood that an amino-acid substitution would have a functional effect. GLI1, GLI2 and PTCH1 were highly expressed in MMe cells, indicative of active HH signaling. PTCH1, SMO and SUFU mutations were found in 2 of 11 MMe cell lines examined. A non-synonymous missense SUFU mutation (p.T411M) was identified in LO68 cells. In silico characterization of the SUFU mutant suggested that the p.T411M mutation might alter protein function. However, we were unable to demonstrate any functional effect of this mutation on Gli activity. Deletion of exons of the PTCH1 gene was found in JU77 cells, resulting in loss of one of two extracellular loops implicated in HH ligand binding and the intracellular C-terminal domain. A 3-bp insertion (69_70insCTG) in SMO, predicting an additional leucine residue in the signal peptide segment of SMO protein was also identified in LO68 cells and a MMe tumour.

CONCLUSIONS/SIGNIFICANCE

We identified the first novel mutations in PTCH1, SUFU and SMO associated with MMe. Although HH pathway mutations are relatively rare in MMe, these data suggest a possible role for dysfunctional HH pathway in the pathogenesis of a subgroup of MMe and help rationalize the exploration of HH pathway inhibitors for MMe therapy.