Abstract LB025: Malat1-Serpinb6b signaling blocks T cells-mediated pyroptosis and governs cancer dormancy metastatic reactivation

Metastatic relapse is the major causes of mortality in patients with cancer and occur due to metastatic reactivation of dormant tumor cells. Early dissemination of tumor cells undergoing a protected period of dormancy in the target organs potentially explains this prevalent clinical behavior. Long non-coding RNAs (lncRNAs) are involved in various biological processes and diseases. Malat1 is one of the most abundant and highly conserved nuclear lncRNAs and have shown the associated with metastasis and serving as a predictive marker for various tumor progression. However, the correlation of tumor intrinsic lncRNAs in regulation of tumor dormancy and immune evasion are largely unknown. Using an in vivo screening platform for the isolation of genetic entities involved in either dormancy or reactivation of breast cancer tumor cells, we have identified Malat1 as a positive mediator of metastatic reactivation. To dissect the functional role of Malat1 in metastatic reactivation, we developed a clean Malat1 knockout (KO) model using paired gRNA CRISPR-Cas9 in metastatic murine syngeneic breast cancer. As a proof of concept, we also used inducible knockdown system under in vivo models. To delineate the immune microenvironment, we used single cell RNA-seq, ChIRP-seq, multicolor flowcytometry, RNA-FISH, and coculture experiments. Our data revealed that deletion of Malat1 induces dormancy and attenuated the metastatic colonization resulting in long-term survival of syngeneic mice model. In contrast, overexpression of Malat1 leads to metastatic reactivation of dormant breast cancer cells. Interestingly, 4T1-Malat1 KO dormant breast cancer cells exhibit metastatic outgrowth in T cells defective mice. Our single-cell RNA-seq and multicolor flowcytometry evaluation reveal enhanced T cells and reduced neutrophils proportions in mice with Malat1 KO cells. This indicates a critical role of immune microenvironment via Malat1-dependent immune evasion. Additionally, Malat1 KO inhibits cancer stemness properties. Similarly, RNA-seq and ChIRP-seq data suggest that KO of Malat1 hampers immune evasion and downregulates metastasis associated genes including Serpins and Wnts. Additionally, our data strongly suggests that Malat1 KO cells persists as non-proliferative dormant cells in lung due to CD8+ T cell-umpired immune activity. Our mechanistic studies showed that Malat1 regulated Sepinb6b blocks the CstG enzymatic activity and suppress cleavage of GsdmD and T cells induced pyroptosis. Interestingly, rescue experiments suggest that Malat1 or Serpinb6b protects T cell-induced cell death and induces dormancy re-awakening thereby rescue the metastatic potential of 4T1 Malat1 KO cells. Combination of Malat1 ASO with double immune checkpoint inhibitors greatly affects the metastatic outgrowth in breast cancer. Taken together, our studies demonstrate that tumor intrinsic Malat1 regulates Serpinb6b that suppresses CstG-GsdmD mediated pyroptosis which eventually promotes immune evasion and breast cancer dormancy metastatic reactivation.

Citation Format: Dhiraj Kumar, Filippo Giancotti. Malat1-Serpinb6b signaling blocks T cells-mediated pyroptosis and governs cancer dormancy metastatic reactivation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB025.

Abstract LB023: Thyroid hormone receptor signaling promotes antiandrogen resistance and bone metastasis in prostate cancer

Background: Systemic factors from the tumor microenvironment (TME) promote prostate cancer (PCa) progression, metastasis, and drug resistance. Therefore, the identification of the systemic factors that can modulate the tumor cells and promote metastases will be critical to improve the efficacy of clinical treatment. Both mechanistic and functional studies revealed that acquisition of an open chromatin state on master regulators or cis-regulatory elements allow them to respond readily to microenvironment signals, thereby increasing cancer cell plasticity, tumorigenicity and malignant potential. Accordingly, analysis of open chromatin regions can help prioritize and identify risk of functionally noncoding variants. Given the power of open chromatin profiling on environmental risk prediction, we hypothesized that analysis of open chromatin regions may enable us to recognize functional trans-regulatory elements with their relevant systemic factors.

Methods and Results: In human prostate cancer cells, AR blockage by enzalutamide can induces cell reprogramming, as well as transcriptional dysregulation of the heterochromatin compaction pathway. Hence, we proposed that the cells were undergoing chromatin decondensation followed by epigenetic reprogramming. To detect the genome-wide open chromatin changes in this process, we performed time course ATAC-seq and H3K27ac ChIP-seq experiments on LNCaP cells treated with enzalutamide over a 2 weeks period. Bioinformatic analysis was performed to identify the “open” enhancers and the transcriptional factors potentially bound to these enhancers. Integrated transcription factor binding motif analysis of metastatic castration-resistant prostate cancer (mCRPC) associated enhancer regions (GSE130408) and multiplexed siRNA screening revealed Thyroid Hormone Receptor Beta (THRB) as the top candidate. THRB is regulated by the thyroid hormone (T3), a systemic nuclear hormone that, in enzalutamide pretreated LNCaP, VCaP and 3PDXs, is able to induce subsequent reprogramming to a fully enzalutamide-resistant and metastatic state. Interestingly, we observed that THRB regulated genes are upregulated in T3-induced resistant prostate cancer cells. Consistently, the THRB protein, TRβ, is abundant in several aggressive PCa cell lines. Notably, knockdown of THRB reverted the growth and the bone metastatic potential of highly aggressive PCa models, such as Ptenpc-/-Smad4pc-/- and PC3M cells. Furthermore, both transcriptomic and functional analyses identified RUNX2 as a transcriptional target of THRB. In summary, we identify a novel mechanism of THRB-mediated tumor progression and drug resistance in PCa cells.

Conclusion: Epidemiologic evidence indicates a higher incidence of PCa in men with elevated thyroid hormone levels. Accordingly, our results suggest a new mechanism for thyroid hormone signaling regulating metastasis potential and drug resistance. This study will provide a new perspective to identify the signals from the TME that may increase the risk of PCa progression.

Citation Format: Yan Wang, Gurrapu Harsha, Dhiraj Kumar, Josue Curto, Xiaobo Wang, Filippo Giancotti. Thyroid hormone receptor signaling promotes antiandrogen resistance and bone metastasis in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB023.

931 LncRNA Malat1 regulated Serpinb6b signaling suppresses pyroptosis and governs breast cancer dormancy reactivation and through immune evasion

Background

Metastatic relapse is the major causes of mortality in patients with cancer and occur due to metastatic reactivation of dormant tumor cells. Early dissemination of tumor cells undergoing a protected period of dormancy in the target organs potentially explains this prevalent clinical behavior.1–4 Long non-coding RNAs (lncRNAs) are involved in various biological processes and diseases. Malat1 is one of the most abundant and highly conserved nuclear lncRNAs and have shown the associated with metastasis and serving as a predictive marker for various tumor progression.5 However, the correlation of tumor intrinsic lncRNAs in regulation of tumor dormancy and immune evasion is largely unknown.

Methods

Using an in vivo screening platform for the isolation of genetic entities involved in either dormancy or reactivation of breast cancer tumor cells, we have identified Malat1 as a positive mediator of metastatic reactivation.4 To dissect the functional role of Malat1 in metastatic reactivation, we developed a clean Malat1 knockout (KO) model using paired gRNA CRISPR-Cas9 in metastatic murine syngeneic breast cancer. As proof of concept we also used inducible knockdown system under in vivo models. To delineate the immune microenvironment, we used single cell RNA-seq, ChIRP-seq, multicolor flowcytometry, RNA-FISH, and coculture experiments.

Results

Our data revealed that deletion of Malat1 induces dormancy and attenuated the metastatic colonization resulting in long-term survival of syngeneic mice model. In contrast, overexpression of Malat1 leads to metastatic reactivation of dormant breast cancer cells. Interestingly, 4T1-Malat1 KO dormant breast cancer cells exhibit metastatic outgrowth in T cells defective mice. Our single-cell RNA-seq and multicolor flowcytometry evaluation reveal enhanced T cells and reduced neutrophils proportions in mice with Malat1 KO cells. This indicates a critical role of immune microenvironment via Malat1-dependent immune evasion. Additionally, Malat1 KO inhibits cancer stemness properties. Similarly, RNA-seq and ChIRP-seq data suggest that KO of Malat1 hampers immune evasion and downregulates metastasis associated genes including Serpins and Wnts. Additionally, our data strongly suggests that Malat1 KO cells persists as non-proliferative dormant cells in lung due to CD8+ T cell-umpired immune activity. Interestingly, rescue experiments suggest that Malat1 or Serpinb6b protects T cell-induced cell death and induces dormancy re-awakening thereby rescue the metastatic potential of 4T1 Malat1 KO cells. Combination of Malat1 ASO with double immune checkpoint inhibitors greatly affects the metastatic outgrowth in breast cancer.

Conclusions

Taken together, our studies demonstrate that tumor intrinsic Malat1 regulates Serpinb6b that eventually controls immune evasion and promote dormancy metastatic reactivation.

Acknowledgements

NGS data generated was supported by Core grant CA016672(ATGC) and NIH 1S10OD024977-01 award to the ATGC. Single cell RNA sequencing data was supported by the CPRIT Single Core grant RP180684. The Advanced Cytometry & Sorting Core Facility is supported by NCI P30CA016672.

References

Arun G, Diermeier S, Akerman M, et al. Differentiation of mammary tumors and reduction in metastasis upon Malat1 lncRNA loss. Genes Dev 2016 January 1;30(1):34–51.

Filippo G Giancotti. Mechanisms governing metastatic dormancy and reactivation. Cell 2013 November 7;155(4):750–764.

Gao H, Chakraborty G, Lee-Lim AP, et al. The BMP inhibitor Coco reactivates breast cancer cells at lung metastatic sites. Cell 2012b;150:764–779.

Gao H, Chakraborty G, Lee-Lim AP, et al. Forward genetic screens in mice uncover mediators and suppressors of metastatic reactivation. Proc Natl Acad Sci U S A 2014 November 18;111(46):16532–16537.

Huang D, Chen J, Yang L, et al. NKILA lncRNA promotes tumor immune evasion by sensitizing T cells to activation-induced cell death. Nat Immunol 2018;19:1112–1125.

Targetable genetic alterations of TCF4 (E2-2) drive immunoglobulin expression in diffuse large B cell lymphoma

The activated B cell (ABC-like) subtype of diffuse large B cell lymphoma (DLBCL) is characterized by chronic activation of signaling initiated by immunoglobulin μ (IgM). By analyzing the DNA copy number profiles of 1000 DLBCL tumors, we identified gains of 18q21.2 as the most frequent genetic alteration in ABC-like DLBCL. Using integrative analysis of matched gene expression profiling data, we found that the TCF4 (E2-2) transcription factor gene was the target of these alterations. Overexpression of TCF4 in ABC-like DLBCL cell lines led to its occupancy on immunoglobulin (IGHM) and MYC gene enhancers and increased expression of these genes at the transcript and protein levels. Inhibition of TCF4 activity with dominant-negative constructs was synthetically lethal to ABC-like DLBCL cell lines harboring TCF4 DNA copy gains, highlighting these gains as an attractive potential therapeutic target. Furthermore, the TCF4 gene was one of the top BRD4-regulated genes in DLBCL cell lines. BET proteolysis-targeting chimera (PROTAC) ARV771 extinguished TCF4, MYC, and IgM expression and killed ABC-like DLBCL cells in vitro. In DLBCL xenograft models, ARV771 treatment reduced tumor growth and prolonged survival. This work highlights a genetic mechanism for promoting immunoglobulin signaling in ABC-like DLBCL and provides a functional rationale for the use of BET inhibitors in this disease.

ACTR-09. A PHASE 0 PHARMACODYNAMIC AND PHARMACOKINETIC STUDY OF EVEROLIMUS IN VESTIBULAR SCHWANNOMA (VS) AND MENINGIOMA PATIENTS

BACKGROUND

Inhibition of mTORC1 signaling has been shown to diminish growth of NF2 deficient tumors in preclinical studies, and clinical data suggest that everolimus, an orally administered mTORC1 inhibitor, may slow tumor progression in a subset of adult and pediatric NF2 patients with VS. To assess the pharmacokinetics, pharmacodynamics and potential mechanisms of treatment resistance, we performed a pre-surgical (“phase 0”) clinical trial of everolimus in patients undergoing surgery for VS or meningiomas.

METHODS

Eligible patients with meningioma or VS requiring tumor resection received everolimus 10 mg daily for 10 days immediately prior to surgery. Everolimus blood levels were determined immediately prior to and after surgery. Tumor samples were collected intraoperatively.

RESULTS

Ten patients completed protocol therapy, including 5 patients with NF2-related meningioma, 3 patients with sporadic meningioma, and 2 patients with NF2-related VS. Median pre- and post-operative plasma levels of everolimus were found to be in a high therapeutic range (17.4 ng/ml and 9.4 ng/ml, respectively). Median tumor tissue drug concentration determined by mass spectrometry was 24.3 ng/g (range 9.2–169.2), and median tumor tissue to post-operative plasma drug concentration ratio was 0.39. We observed only partial inhibition of phospho-S6 in the treated tumors, indicating incomplete target inhibition compared to matched control tissues from untreated patients (p = 0.005). Consistent with prior observations that inhibition of mTORC1 may lead to MAPK pathway activation through a PI3K-dependent feedback loop, we observed a statistically significant increase of phospho-ERK (p < 0.03) versus untreated controls.

CONCLUSIONS

In patients with meningioma or VS, treatment with everolimus leads to incomplete inhibition of mTORC1 signaling and upregulation phospho-ERK. These data may explain the limited anti-tumor effect of everolimus observed in clinical studies for NF2 patients and identify upregulation of phospho-ERK as a likely resistance mechanism that could be addressed with combination therapies.

NF2 Loss Promotes Oncogenic RAS-Induced Thyroid Cancers via YAP-Dependent Transactivation of RAS Proteins and Sensitizes Them to MEK Inhibition

Ch22q LOH is preferentially associated with RAS mutations in papillary and in poorly differentiated thyroid cancer (PDTC). The 22q tumor suppressor NF2, encoding merlin, is implicated in this interaction because of its frequent loss of function in human thyroid cancer cell lines. Nf2 deletion or Hras mutation is insufficient for transformation, whereas their combined disruption leads to murine PDTC with increased MAPK signaling. Merlin loss induces RAS signaling in part through inactivation of Hippo, which activates a YAP-TEAD transcriptional program. We find that the three RAS genes are themselves YAP-TEAD1 transcriptional targets, providing a novel mechanism of promotion of RAS-induced tumorigenesis. Moreover, pharmacologic disruption of YAP-TEAD with verteporfin blocks RAS transcription and signaling and inhibits cell growth. The increased MAPK output generated by NF2 loss in RAS-mutant cancers may inform therapeutic strategies, as it generates greater dependency on the MAPK pathway for viability.

SIGNIFICANCE

Intensification of mutant RAS signaling through copy-number imbalances is commonly associated with transformation. We show that NF2/merlin inactivation augments mutant RAS signaling by promoting YAP/TEAD-driven transcription of oncogenic and wild-type RAS, resulting in greater MAPK output and increased sensitivity to MEK inhibitors.

Abstract 2896: A flexible mouse model of malignant pleural mesothelioma

Patients with advanced malignant pleural mesothelioma (MPM) have extremely limited treatment options. To develop targeted therapies necessary to radically alter the clinical course of MPM, it is important to identify oncogenic mutations and signaling pathways that drive its development and progression. About 75% of MPMs carry inactivating mutations at the NF2 locus, which encodes the FERM domain protein Merlin, and often also have deletions of the CDKN2A locus, encoding the CDK inhibitor p16 and the p53 activator ARF. Since traditional cancer therapies target dysregulated oncogenes, it is important to elucidate the pathogenically relevant proteins that are dysregulated downstream of MPM tumor suppressors. We have developed a flexible and rapid mouse model that can be used to dissect genetics of MPM, to evaluate the preclinical efficacy of novel therapies, and to provide a platform for MPM shRNA genetic screens. We injected into the pleural cavity of mice lentivirus encoding Cre recombinase and miR30-based shRNA cassettes to simultaneously deplete four of the most commonly lost proteins in mesothelioma - Nf2, p16INK4a/ARF, and BAP1. Cre recombinase deletes the Nf2 conditional allele and simultaneously activates a Luciferase reporter gene in the pleural mesothelium, allowing for bioluminescent imaging of infected cells that develop MPM tumors. Lentiviral miR30-based shRNA cassettes simultaneously deplete Ink4a/ARF and Bap1, helping to drive tumorigenesis. To evaluate MPM genetics, mice with conditional alleles for putative drivers of MPM pathogenesis (i.e. Dcaf1 and Ptk2) in addition to the Nf2 conditional allele can be injected with the virus to determine whether these genes are necessary and sufficient for MPM development or progression. Moreover, knockdown of putative MPM drivers can be easily carried out by adding corresponding shRNA cassettes to the lentiviral vector. Using these methods, we have developed a rapid genetically engineered mouse model that recapitulates human MPM and can be used to explore MPM genetics. This flexible MPM mouse model will allow us to unravel MPM genetics and help to identify novel therapeutic targets as well as provide an efficient preclinical test of these therapies.

Citation Format: Jonathan Cooper, Filippo Giancotti. A flexible mouse model of malignant pleural mesothelioma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2896. doi:10.1158/1538-7445.AM2015-2896

Abstract 4722: Inactivation of neogenin promotes castration resistance and bone metastasis in prostate cancer models

Increasing evidence suggests that exposure to new generation agents targeting the AR promotes the emergence of castration-resistant stem-like clones ultimately leading to treatment failure. In order to develop improved therapies for castration-resistant prostate cancer (CRPC), it is important to understand the origin and biology of these stem-like clones. We have observed significantly diminished levels of Neogenin (encoded by NEO1) in CRPC. Neogenin functions as a neuronal guidance receptor but has also been implicated in epithelial branching morphogenesis and is homologous to DCC, which functions as a suppressor of tumor progression in breast and colorectal cancer. We found that silencing of neogenin induces androgen receptor (AR) dependent prostate cancer cells to undergo an epithelial to mesenchymal transition (EMT) and acquire neuroendocrine (NE) differentiation features. In addition, the neogenin-silenced cells expressed high levels of the stem cell markers β4 integrin and CD44 and formed rapidly growing tumor spheres in vitro. Intriguingly, these cells had become castration resistant due to loss of AR expression and were able to efficiently colonize the bone upon intracardiac injection in immunodeficient mice. Genomic and molecular pathology studies indicated that NEO1 expression is lost in CRPC and NEPC. To examine the relationship between the acquisition of the castration resistant phenotype and loss of neogenin, we have generated a series of casodex- and enzalutamide-resistant clones from LNCaP cells. Interestingly, we observed that a significant fraction of these clones have lost expression of neogenin and acquired expression of the β4 integrin and are highly metastatic in immunodeficient mice, similar to the characteristics of CRPC observed in the clinic. To validate these results, we sought to identify a population of β4-positive cells in the peripheral blood of patients with CRPC. By using immunofluorescent staining and FACS analysis, we were able to identify β4-positive circulating tumor cells (CTCs) from the peripheral blood of CRPC patients. These cells were not detected in the blood of healthy normal donors but their numbers increased with disease progression. These findings identify a novel tumor progression pathway that is likely to operate in at least a fraction of CRPC cases.

Citation Format: Goutam Chakraborty, Mayur Gadiya, Myriam Kossai, Dong Gao, Weijing Su, Hua Gao, Yu Chen, Howard I. Scher, Mark A. Rubin, Filippo Giancotti. Inactivation of neogenin promotes castration resistance and bone metastasis in prostate cancer models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4722. doi:10.1158/1538-7445.AM2015-4722

Abstract A34: GDC-0980, a dual PI3K/mTOR inhibitor, selectively inhibits NF2 mutant malignant mesothelioma (MM) cells and inhibits TOR signaling without activating Akt or ERK

Purpose: Inactivation of Merlin/NF2 is common, occurring in 45-60% of mesotheliomas. Merlin loss leads to hyperactivation of TOR signaling and dysregulation of this pathway drives tumor development and growth. Cytostatic inhibition of TOR with rapamycin in MM cells has limited impact (Lopez-Lago Mol Cell Biol 2009). Rapamycin releases two major negative feedback loops that restrain Akt-TOR signaling, thereby leading to hyperactivation of both Akt and ERK. Effective growth inhibition likely requires dual inhibition of PI3K and mTOR. We therefore sought to assess the activity of the potent and selective dual PI3K/mTOR inhibitor GDC-0980 in MM cells with respect to cell proliferation and hyperactivation of Akt and ERK.

Experimental Procedures: NF2 mutant cell lines, VAMT and JMN, and NF2 wild type cell lines, H-Meso and 211-H, were cultured in the presence of increasing concentrations of GDC-0980 for 48 hours and subjected to MTT assay. Values were normalized to untreated samples at day 0. Meso 33 and JMN malignant mesothelioma cell lines were treated with increasing doses of GDC-0980 for 2 hours and subjected to immunoblotting for P-S6, P-4E-BP1, P-Akt (S473), P-ERK, and ERK2.

Results: GDC-0980 effectively inhibited proliferation of the NF2 mutant cell lines by 40% but had little or no effect on NF2 wild type cell lines (statistically significant difference at 80 nM with p&lt;0.006). 100 nM GDC-0980 completely suppresses activation of TOR as assessed by phosphorylation of S6 and 4E-BP1 in Meso-33 cells. Higher concentrations were required for these events in JMN cells. However, in both Meso-33 and JMN cells, these effects were not associated with overactivation of Akt or ERK.

Conclusions: GDC-0980 is a potent inhibitor of proliferation in MM cells with NF2 mutations and does not cause hyperactivation of Akt and ERK. Along with our ongoing preclinical work with cell lines and xenograft mouse models, the data from a recent phase I clinical trial with an expansion cohort in mesothelioma (NCT00854152) provide a strong rationale for the development of biomarker-driven clinical trials of GDC-0980 and other PI3K/mTOR inhibitors in mesothelioma.

This work was supported in part by Genentech.

Citation Format: Marjorie G. Zauderer, Kamalika Moulik, Jonathan Cooper, Lee M. Krug, Filippo Giancotti. GDC-0980, a dual PI3K/mTOR inhibitor, selectively inhibits NF2 mutant malignant mesothelioma (MM) cells and inhibits TOR signaling without activating Akt or ERK. [abstract]. In: Proceedings of the AACR Special Conference: Targeting the PI3K-mTOR Network in Cancer; Sep 14-17, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(7 Suppl):Abstract nr A34.

Functionally distinct PI 3-kinase pathways regulate myelination in the peripheral nervous system

The PI 3-kinase (PI 3-K) signaling pathway is essential for Schwann cell myelination. Here we have characterized PI 3-K effectors activated during myelination by probing myelinating cultures and developing nerves with an antibody that recognizes phosphorylated substrates for this pathway. We identified a discrete number of phospho-proteins including the S6 ribosomal protein (S6rp), which is down-regulated at the onset of myelination, and N-myc downstream-regulated gene-1 (NDRG1), which is up-regulated strikingly with myelination. We show that type III Neuregulin1 on the axon is the primary activator of S6rp, an effector of mTORC1. In contrast, laminin-2 in the extracellular matrix (ECM), signaling through the α6β4 integrin and Sgk1 (serum and glucocorticoid-induced kinase 1), drives phosphorylation of NDRG1 in the Cajal bands of the abaxonal compartment. Unexpectedly, mice deficient in α6β4 integrin signaling or Sgk1 exhibit hypermyelination during development. These results identify functionally and spatially distinct PI 3-K pathways: an early, pro-myelinating pathway driven by axonal Neuregulin1 and a later-acting, laminin-integrin-dependent pathway that negatively regulates myelination.

New strategies in pleural mesothelioma: BAP1 and NF2 as novel targets for therapeutic development and risk assessment

Malignant pleural mesothelioma (MPM) is a highly lethal cancer with limited therapeutic options. Recent work has focused on the frequent somatic inactivation of two tumor suppressor genes in MPM-NF2 (Neurofibromatosis type 2) and the recently identified BAP1 (BRCA associated protein 1). In addition, germline mutations in BAP1 have been identified that define a new familial cancer syndrome, which includes MPM, ocular melanoma, and other cancers. These recent advances may allow screening of high-risk individuals and the development of new therapies that target key pathways in MPM.

Neurofibromatosis 2011: a report of the Children's Tumor Foundation annual meeting

The 2011 annual meeting of the Children’s Tumor Foundation, the annual gathering of the neurofibromatosis (NF) research and clinical communities, was attended by 330 participants who discussed integration of new signaling pathways into NF research, the appreciation for NF mutations in sporadic cancers, and an expanding pre-clinical and clinical agenda. NF1, NF2, and schwannomatosis collectively affect approximately 100,000 persons in US, and result from mutations in different genes. Benign tumors of NF1 (neurofibroma and optic pathway glioma) and NF2 (schwannoma, ependymoma, and meningioma) and schwannomatosis (schwannoma) can cause significant morbidity, and there are no proven drug treatments for any form of NF. Each disorder is associated with additional manifestations causing morbidity. The research presentations described in this review covered basic science, preclinical testing, and results from clinical trials, and demonstrate the remarkable strides being taken toward understanding of and progress toward treatments for these disorders based on the close interaction among scientists and clinicians.

Molecular characterization of the tumor-suppressive function of nischarin in breast cancer

BACKGROUND

Nischarin (encoded by NISCH), an α5 integrin-binding protein, has been identified as a regulator of breast cancer cell invasion. We hypothesized that it might be a tumor suppressor and were interested in its regulation.

METHODS

We examined nischarin expression in approximately 300 human breast cancer and normal tissues using quantitative polymerase chain reaction and immunohistochemistry. Loss of heterozygosity analysis was performed by examining three microsatellite markers located near the NISCH locus in normal and tumor tissues. We generated derivatives of MDA-MB-231 human metastatic breast cancer cells that overexpressed nischarin and measured tumor growth from these cells as xenografts in mice; metastasis by these cells after tail vein injection; and α5 integrin expression, Rac, and focal adhesion kinase (FAK) signaling using western blotting. We also generated clones of MCF-7 human breast cancer cells in which nischarin expression was silenced and measured tumor growth in mouse xenograft models (n = 5 for all mouse experiments). P values were from two-sided Student t tests in pairwise comparisons.

RESULTS

Normal human breast tissue samples had statistically significantly higher expression of nischarin mRNA compared with tumor tissue samples (mean level in normal breast = 50.7 [arbitrary units], in breast tumor = 16.49 [arbitrary units], difference = 34.21, 95% confidence interval [CI] = 11.63 to 56.79, P = .003), and loss of heterozygosity was associated with loss of nischarin expression. MDA-MB-231 cells in which nischarin was overexpressed had statistically significantly reduced tumor growth and metastasis compared with parental MDA-MB-231 cells (mean volume at day 40, control vs nischarin-expressing tumors, 1977 vs 42.27 mm(3), difference = 1935 mm(3), 95% CI = 395 to 3475 mm(3), P = .025). Moreover, MCF-7 tumor xenografts in which nischarin expression was silenced grew statistically significantly faster than parental cells (mean volume at day 63, tumors with scrambled short hairpin RNA [shRNA] vs with nischarin shRNA, 224 vs 1262 mm(3), difference = 1038 mm(3), 95% CI = 899.6 to 1176 mm(3), P < .001). Overexpression of nischarin was associated with decreased α5 integrin expression, FAK phosphorylation, and Rac activation.

CONCLUSION

Nischarin may be a novel tumor suppressor that limits breast cancer progression by regulating α5 integrin expression and subsequently α5 integrin-, FAK-, and Rac-mediated signaling.

Celiac disease, primary biliary cirrhosis and helicobacter pylori infection: one link for three diseases

The association between celiac disease (CD) and primary biliary cirrhosis (PBC) has been reported in literature. Recent epidemiological studies showed an increased prevalence of CD in patients with PBC and vice versa. The cause of PBC is unknown. However, considerable evidence points to an autoimmune basis. The role of infectious agents, such as Helicobacter pylori (H. pylori), has been proposed to stimulate antibody cross-reaction with mitochondria of the bile duct cells. We report a case of a 36-year-old woman with diagnosis of CD, PBC and H. pylori infection. Strict adherence to gluten-free diet, associated to ursodeoxycholic acid (UDCA) administration and eradication treatment for H. pylori infection, led to a marked improvement of clinical status. Our experience supports the pathogenetic role of increased intestinal permeability in the course of CD and H. pylori infection to induce PBC. Future studies are needed to clarify this link to, and in particular the role played by abnormal intestinal permeability and infectious agents in the pathogenesis of PBC.

Hepatitis C virus cirrhosis: prolonged sustained virological response in a patient after low-dose antiviral treatment

Hepatitis C virus (HCV) infection is the most frequent cause of chronic liver disease in the western world. The ''gold standard'' treatment of chronic HCV infection currently involves the administration of pegylated interferon alpha (PEG-IFN) and ribavirin. The success of this therapy is demonstrated by sustained virological responses (SVR). Randomized trials and practice guidelines have reported that compensated HCV cirrhosis is an indication for treatment with PEG-IFN and ribavirin, not only to obtain SVR but also to increase survival and to reduce the development of cirrhotic sequelae. In particular, the literature has reported that antiviral treatment was associated with histological improvement of fibrosis in cirrhotic patients with SVR. Recently, the same authors have evaluated the efficacy and safety of different doses of antiviral treatment in patients with chronic HCV infection. The use of interferon has been limited due to associated side effects, particularly in cirrhotic patients. Consequently, therapeutic decisions should be made on an individual basis. The Authors report a case of a patient with compensated HCV liver cirrhosis, with associated severe thrombocytopenia and oesophageal varices, in which the administration of antiviral therapy at a dose lower than the therapeutic ''gold standard'' has achieved SVR and consequently improved clinical status.

p130Rb2 and p27kip1 cooperate to control mobilization of angiogenic progenitors from the bone marrow

Neoangiogenesis involves both bone marrow-derived myelomonocytic and endothelial progenitor cells as well as endothelial cells coopted from surrounding vessels. Cytokines induce these cells to proliferate, migrate, and exit the cell cycle to establish the vasculature; however, which cell cycle regulators play a role in these processes is largely unknown. Here, we report that mice lacking the cell cycle inhibitors p130 and p27 show defects in tumor neoangiogenesis, both in xenografts and spontaneously arising tumors. This defect is associated with impaired mobilization of endothelial and myelomonocytic angiogenic progenitors from the bone marrow. This article documents the role of these molecules in angiogenesis and further suggests that cell expansion and mobilization from the bone marrow of angiogenic precursors are separable events.

beta4 integrin-dependent formation of polarized three-dimensional architecture confers resistance to apoptosis in normal and malignant mammary epithelium

Tumor cells can evade chemotherapy by acquiring resistance to apoptosis. We investigated the molecular mechanism whereby malignant and nonmalignant mammary epithelial cells become insensitive to apoptosis. We show that regardless of growth status, formation of polarized, three-dimensional structures driven by basement membrane confers protection to apoptosis in both nonmalignant and malignant mammary epithelial cells. By contrast, irrespective of their malignant status, nonpolarized structures are sensitive to induction of apoptosis. Resistance to apoptosis requires ligation of beta4 integrins, which regulates tissue polarity, hemidesmosome formation, and NFkappaB activation. Expression of beta4 integrin that lacks the hemidesmosome targeting domain interferes with tissue polarity and NFkappaB activation and permits apoptosis. These results indicate that integrin-induced polarity may drive tumor cell resistance to apoptosis-inducing agents via effects on NFkappaB.

Alpha3beta1-integrin as a critical mediator of the hepatic differentiation response to the extracellular matrix

The extracellular matrix (ECM) promotes the differentiation of many cell types, and ECM remodeling in the liver has been implicated in embryonic development, tissue injury, and oncogenesis. Integrins are heterodimeric ECM receptors that play critical roles in transducing the composition of the ECM in the cell environment. We previously showed that mouse H2.35 cells, a conditionally transformed, liver-derived cell line, assume a more differentiated hepatocyte morphology and enhanced liver-specific gene expression when the cells are cultured on gelatinous ECM substrata. Here we show that H2. 35 cells express relatively high levels of alpha3beta1-integrins, similar to that previously shown for immature hepatocytes, transformed hepatocytes, and biliary cells. However, the cell morphological responses that depend on alpha3beta1-integrin have not been defined. We found that transfecting H2.35 cells with antisense RNA construct directed to alpha3-subunit messenger RNA perturbs the initial cell attachment to laminin and collagen, and strongly inhibits cell morphological, proliferative, and gene expression responses to a collagen gel substratum. In situ hybridization to mouse embryo tissues demonstrates the presence of alpha3-subunit messenger RNAs in newly formed hepatocytes. We suggest that alpha3beta1-integrins are important for immature and transformed hepatocytes to respond morphologically to the extracellular matrix.

EBV-associated primary lymphomas in salivary glands of HIV-infected patients

The lymph nodes within and around salivary glands are commonly involved in inflammatory processes, but rarely the site of primary lymphomas. We observed six cases of primary salivary gland lymphoma in HIV-infected patients and studied them in parallel with three cases of primary salivary gland lymphoma unrelated to HIV and three cases of HIV-related salivary gland lymphadenopathies in order to characterize this new entity. We found that all salivary gland lymphomas in HIV-infected patients were of high histologic grade while salivary gland lymphomas unrelated to HIV were predominantly of low grade MALT type. All lymphomas in both categories expressed the B-cell phenotype. Just as HIV-unrelated lymphomas frequently arise on the background of chronic inflammatory lymphoid processes, lesions characteristic of HIV-lymphadenopathy were still present in some lymphomas of HIV-infected patients. EBV RNA transcripts (EBER) were demonstrated in three, and latent membrane protein (LMP) in two of the six HIV-related and in none of the three HIV-unrelated lymphomas. The three EBER-positive lymphomas were of the histologic types known to express the virus in most cases. The presence of HIV in the form of the core protein p24 and envelope glycoprotein gp41 on the dendritic reticular cells of germinal centers was ascertained in the cases of HIV-related lymphadenopathies but also in the coexistent lymphadenopathies of lymphomas. The practical importance of diagnosing the salivary lymphadenopathies and lymphomas associated with the HIV-infection resides in avoiding their misdiagnosis and surgical removal as tumors of salivary glands.

EBV-associated anorectal lymphomas in patients with acquired immune deficiency syndrome

Primary lymphomas of the gastrointestinal tract represent 9% of all non-Hodgkin lymphomas, and of these only 3% arise in the rectum or anus. In contrast to their rare occurrence in the general population, the incidence of anorectal lymphomas in patients with acquired immune deficiency syndrome (AIDS), particularly homosexual patients, may be as high as 26% as reported in our own series of AIDS-associated lymphomas. To determine the characteristics of this entity, we studied 15 cases of primary anorectal lymphoma in AIDS patients and compared them with four cases of anorectal lymphoma unrelated to AIDS. The cases in our study were also compared with the reports of rectal lymphoma in the medical literature over the past 30 years. In the present series, the AIDS patients were all male with a median age of 34 years, human immunodeficiency virus (HIV)-positive, with homosexuality as the main risk factor. The four non-AIDS patients included a woman and had a median age of 66.5 years. Histologically, the anorectal lymphomas in AIDS patients were all high grade, predominantly immunoblastic, and polymorphous. In the non-AIDS patients, only two of four lymphomas were high grade, including one Burkitt type. All tumors were of B-cell phenotype. In the AIDS-associated anorectal lymphomas, the presence of Epstein-Barr virus (EBV) in a latent form was demonstrated by an abundance of Epstein-Barr-encoded RNA (EBER) in 14 of 15 cases and latent membrane protein (LMP) in four cases. All anorectal lymphomas unrelated to AIDS were negative for EBV. The unusual anorectal location of AIDS-associated lymphomas is explainable by the high incidence of preceding traumatic lesions and chronic infections in the area. As a result, EBV-carrying B cells may be attracted to the field providing the cell population that, under the conditions of immune deficiency, is able to give rise to high-grade lymphomas.

Transfection of beta 4 integrin subunit into a neoplastic keratinocyte line fails to restore terminal differentiation capacity or influence proliferation

Loss of expression of specific integrins is a feature of poorly differentiated oral squamous cell carcinomas (SCCs) and cell lines derived from them. In order to test whether there is a direct link between reduced alpha 6 beta 4 integrin expression and abnormal keratinocyte growth and differentiation we 'repaired' an SCC line. H376, by transfection of the beta 4 integrin subunit. We analysed five independent beta 4 transfectant clones and compared them with four empty vector control clones and with the parental cell line. Elevated cell surface expression of alpha 6 beta 4 was not correlated with changes in anchorage dependent or independent growth and was not sufficient to induce expression of the terminal differentiation marker, involucrin. Introduction of the beta 4 integrin subunit did not have a major effect on cell adhesion to laminin 1 or 5 and did not result in formation of stable anchoring contacts. We conclude that loss of alpha 6 beta 4 is not directly responsible for the abnormal behaviour of the H376 cell line.

Reactivity of lung tumors with lung-derived and non-lung-derived monoclonal antibodies

The reactivity of 74 lung-derived monoclonal antibodies (MAbs) provided by the Third International Workshop on Lung Tumor Antigens and of 41 non-lung-derived commercially available MAbs against sections of 15 lung tumors of various histologic types was investigated by immunohistochemistry. Three MAbs with specificity for human neural-cell adhesion molecule (H-NCAM) and 3 MAbs with specificity for small-cell lung carcinoma (SCLC) were able to distinguish between neuro-endocrine (NE) and non-NE tumors. Fifteen MAbs stained non-small-cell carcinomas (NSCLC) but not SCLC. Neuron-specific enolase (NSE) stained all NE tumors but also some of the non-NE tumors. Two MAbs showed specificity for mesotheliomas. Carcino-embryonic MAb strongly stained all SCLC and NSCLC. Among MAbs with lymphoid-cell specificities, Leu 7 (CD57) stained SCLC, but not NSCLC. LN2 (CD45R), LN3 (HLA-DR), Leu 22 (CD43) and BLA 36 reacted with NSCLC and were non-reactive with SCLC. Some of the lung-derived MAbs showed immune staining of lymphoma and melanoma.

Axonal regulation of Schwann cell integrin expression suggests a role for alpha 6 beta 4 in myelination

Ensheathment and myelination of axons by Schwann cells in the peripheral nervous system requires contact with a basal lamina. The molecular mechanism(s) by which the basal lamina promotes myelination is not known but is likely to reflect the activity of integrins expressed by Schwann cells. To initiate studies on the role of integrins during myelination, we characterized the expression of two integrin subunits, beta 1 and beta 4, in an in vitro myelination system and compared their expression to that of the glial adhesion molecule, the myelin-associated glycoprotein (MAG). In the absence of neurons, Schwann cells express significant levels of beta 1 but virtually no beta 4 or MAG. When Schwann cells are cocultured with dorsal root ganglia neurons under conditions promoting myelination, expression of beta 4 and MAG increased dramatically in myelinating cells, whereas beta 1 levels remained essentially unchanged. (In general agreement with these findings, during peripheral nerve development in vivo, beta 4 levels also increase during the period of myelination in sharp contrast to beta 1 levels which show a striking decrease.) In cocultures of neurons and Schwann cells, beta 4 and MAG appear to colocalize in nascent myelin sheaths but have distinct distributions in mature sheaths, with beta 4 concentrated in the outer plasma membrane of the Schwann cell and MAG localized to the inner (periaxonal) membrane. Surprisingly, beta 4 is also present at high levels with MAG in Schmidt-Lanterman incisures. Immunoprecipitation studies demonstrated that primary Schwann cells express beta 1 in association with the alpha 1 and alpha 6 subunits, while myelinating Schwann cells express alpha 6 beta 4 and possibly alpha 1 beta 1. beta 4 is also downregulated during Wallerian degeneration in vitro, indicating that its expression requires continuous Schwann cell contact with the axon. These results indicate that axonal contact induces the expression of beta 4 during Schwann cell myelination and suggest that alpha 6 beta 4 is an important mediator of the interactions of myelinating Schwann cells with the basal lamina.

[Mechano-electric feedback and ventricular arrhythmias in heart failure. The possible role of permanent cardiac stimulation in preventing ventricular tachycardia]

Left ventricular dysfunction has been identified as the strongest independent predictor of sudden death in patients with ventricular tachyarrhythmias. It has been suggested that some of these arrhythmias might be due to myocardial stretch which may alter cellular electrophysiological properties. In heart failure (HF) the abnormal mechanics of contraction may directly initiate an arrhythmia by mechano-electric feedback (MEF), defined as changes in mechanical state that precede and alter transmembrane potential. So far, the significance of MEF and its role in clinical arrhythmogenesis have received minimal attention. We report data of 3 patients, aged from 60 to 64 years (mean age 62 +/- 2), affected by HF from 28.3 +/- 3.5 months and ventricular arrhythmias recorded by Holter: premature contractions, couplets, nonsustained ventricular tachycardia (VT). Sinus rhythm was present in 2 patients, atrial fibrillation in the last one. Many VT episodes started after an abrupt spontaneous increase in ventricular cycle length or following an ectopic beat. A permanent VVI pacemaker (MEDTRONIC Legend) was implanted in each patient and programmed at different rate from 50 to 80 b/min. During the upper rates, 70 and 80 b/min, VT episodes decreased from 292 +/- 181 to 161 +/- 95 and 97 +/- 63 (p < 0.05), respectively. In fact, the permanent pacemaker could prevent the lengthening of ventricular cycle and the myocardial fibers stretch due to the increase in ventricular volume. In conclusion, in patients with HF and ventricular arrhythmias a pacemaker may be useful in preventing VT episodes and, probably, sudden death.

Nerve growth factor induces increased expression of a laminin-binding integrin in rat pheochromocytoma PC12 cells

Rat pheochromocytoma PC12 cells exposed to nerve growth factor differentiate as sympathetic neurons and extend neurites on laminin and to a much lesser extent on fibronectin. Analysis of laminin fragments indicated that neurite outgrowth occurs mainly on fragment P1, corresponding to the center of the cross, and only poorly on fragment E8, a long arm structure that is active with other neuronal cells. Integrin antibodies prevented adhesion and neurite sprouting of these cells on laminin, fragment P1, and fibronectin. By affinity chromatography we isolated an integrin-type receptor for laminin consisting of two subunits with molecular massess of 180 and 135 kDa. The latter is recognized by an antiserum to integrin beta 1 subunit. The bound laminin receptor could be displaced by EDTA, but not by Arg-Gly-Asp or Tyr-Ile-Gly-Ser-Arg peptides. Affinity chromatography on laminin fragments showed that the 180/135 kDa receptor binds to P1. The expression of the 180-kDa alpha subunit of the laminin receptor at the cell surface was increased 10-fold after NGF treatment. The effect of NGF is specific since the amount of a 150-kDa fibronectin-binding integrin alpha subunit remained unchanged. Moreover, the increased expression of the 180/135 kDa receptor at the cell surface corresponded to a selective increase in cell adhesion to laminin and to fragment P1. The 180/135-kDa complex is thus an integrin-type receptor for laminin whose expression and binding specificity correlates with the capacity of NGF-induced PC12 cells to extend neurites on laminin.

[Space analysis and treatment planning in the mixed dentition]

The maintaining of the space during mixed dentition, allows the patient to obtain a good occlusion, the right growth and facial development. The orthodontist can preserve the space, using simple appliances like the lip bumper and the lingual arch.

Cloning of cDNA for a novel mouse membrane glycoprotein (gp42): shared identity to histocompatibility antigens, immunoglobulins and neural-cell adhesion molecules

A full-length clone encoding a murine membrane glycoprotein, gp42, was selected from a mouse fibroblast cDNA expression library by screening with a polyclonal antiserum. The deduced amino acid (aa) sequence indicates that gp42 is a transmembrane protein of 273 aa with a large N-terminal portion exposed outside the cell and a short cytoplasmic domain. Computer assisted analysis shows that gp42 is distinct from previously characterized proteins, but shares a number of structural features with the class II histocompatibility antigens. The sizes of the extracellular domains of gp42 and of class II histocompatibility antigens are similar, the position of four cysteines and the location of several aa residues are conserved. Some of these conserved residues are also present in immunoglobulins (Ig) and in the neural-cell adhesion molecule, thus indicating that gp42 is a new member of the Ig superfamily.

Interaction of fibronectin with cultured human endothelial cells: characterization of the specific receptor

In this study we provide a characterization of the fibronectin (FN) binding to endothelial cells (EC), and we identify the FN binding site on these cells. 125I-FN binding to EC in suspension was time dependent and reached a plateau at 4 h. Cold FN inhibited this interaction in a concentration-dependent way, but vitronectin, fibrinogen, and IgG were poorly effective. About 80% of the total FN associated to EC at the equilibrium was specifically bound; of this, 60% was reversibly bound, while 20% appeared to be internalized. The FN binding was saturable and an apparent dissociation constant of about 0.23 x 10(-6) mol/L and a maximal number of binding sites of about 9.8 x 10(5) was estimated from binding isotherms. Autoradiography data showed that EC-associated 125I-FN was all in high mol wt form that did not enter the gel. We then characterize the FN receptor (FNR) in EC. An antiserum to the FNR isolated from human placenta inhibited FN binding to EC by 89%, and using the immunoblotting technique, it recognized two bands in the EC detergent extract of mol wt 125/160 Kd. This antiserum also recognized the EC membrane protein complex eluted from the FN affinity column by an arg-gly-asp (RGD) peptide. When this complex was included into liposomes, it poorly bound to FN. However, the binding was strikingly increased by addition of Mn in the buffer and was specific for FN in respect to other substrata. These data define the FN binding site in EC and indicate that it is functionally and structurally related to that isolated from human placenta.

Inhibition of experimental metastasis of murine fibrosarcoma cells by oligopeptide analogues to the fibronectin cell-binding site

We have analyzed the effect of the synthetic oligopeptides Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) and Gly-Arg-Gly-Glu-Ser-Pro (GRGESP), analogues to the fibronectin cell-binding sequence, on the formation of experimental lung metastasis. SR-BALB were injected alone or in conjunction with GRGDSP or GRGESP in the tail vein of BALB/c mice. Co-injection with GRGESP reduced by approximately 70% the number of metastatic colonies per mouse. However, co-injection with the closely related peptide GRGDSP, containing the conservative substitution Glu/Asp, did not affect metastatic behavior. GRGESP peptide anti-metastatic activity was not due to a toxic effect on tumor cells or on mice. In vitro adhesion assays testing for a possible effect of the peptide on cell-matrix interactions indicated that the GRGESP peptide did not affect cell adhesion to the matrix proteins tested.

Chemotaxis of 3T3 and SV3T3 cells to fibronectin is mediated through the cell-attachment site in fibronectin and a fibronectin cell surface receptor

Fibronectin (FN) is a multidomain extracellular matrix protein that induces attachment and chemotactic migration of fibroblastic cells. In this study we analyzed the molecular determinants involved in the FN-induced chemotactic migration of normal and SV40-transformed 3T3 cells. Two different monoclonal antibodies to the cell-binding site of FN blocked chemotaxis to a 140-kD FN fragment (Ca 140) containing the cell-binding domain. A monoclonal antibody to a determinant distant from the cell-binding site did not affect chemotaxis. A synthetic tetrapeptide, RGDS, which represents the major cell-attachment sequence, was able to compete with FN and the Ca 140 fragment in chemotaxis assays, but this peptide itself had no significant chemotactic activity. A larger peptide encompassing this sequence, GRGDSP, was chemotactic, while the peptide GRGESP, where a glutamic acid residue was substituted for aspartic acid, was inactive. Chemotactic migration could be prevented in a dose-dependent manner by a rabbit polyclonal antiserum to a 140-kD cell surface FN receptor. This antibody was more effective on normal than on transformed 3T3 cells. Neither the anti-FN receptor antiserum nor a monoclonal antibody to the cell-binding site of FN blocked migration induced by another potent chemoattractant, platelet-derived growth factor. These data indicate that FN-induced chemotaxis of 3T3 and SV3T3 cells is mediated via the RGDS cell-attachment site of FN and the 140-kD cell surface FN receptor. The interaction is specific and can be altered by transformation.