In vivo CRISPR screens reveal Serpinb9 and Adam2 as regulators of immune therapy response in lung cancer.

How the genetic landscape governs a tumor's response to immunotherapy remains poorly understood. To assess the immune-modulatory capabilities of 573 genes associated with altered cytotoxicity in human cancers, here we perform CRISPR/Cas9 screens directly in mouse lung cancer models. We recover the known immune evasion factors Stat1 and Serpinb9 and identify the cancer testis antigen Adam2 as an immune modulator, whose expression is induced by KrasG12D and further elevated by immunotherapy. Using loss- and gain-of-function experiments, we show that ADAM2 functions as an oncogene by restraining interferon and TNF cytokine signaling causing reduced presentation of tumor-associated antigens. ADAM2 also restricts expression of the immune checkpoint inhibitors PDL1, LAG3, TIGIT and TIM3 in the tumor microenvironment, which might explain why ex vivo expanded and adoptively transferred cytotoxic T-cells show enhanced cytotoxic efficacy in ADAM2 overexpressing tumors. Together, direct in vivo CRISPR/Cas9 screens can uncover genetic alterations that control responses to immunotherapies.

Loss of Epigenetic Regulation Disrupts Lineage Integrity, Induces Aberrant Alveogenesis, and Promotes Breast Cancer.

Systematically investigating the scores of genes mutated in cancer and discerning disease drivers from inconsequential bystanders is a prerequisite for precision medicine but remains challenging. Here, we developed a somatic CRISPR/Cas9 mutagenesis screen to study 215 recurrent "long-tail" breast cancer genes, which revealed epigenetic regulation as a major tumor-suppressive mechanism. We report that components of the BAP1 and COMPASS-like complexes, including KMT2C/D, KDM6A, BAP1, and ASXL1/2 ("EpiDrivers"), cooperate with PIK3CAH1047R to transform mouse and human breast epithelial cells. Mechanistically, we find that activation of PIK3CAH1047R and concomitant EpiDriver loss triggered an alveolar-like lineage conversion of basal mammary epithelial cells and accelerated formation of luminal-like tumors, suggesting a basal origin for luminal tumors. EpiDriver mutations are found in ∼39% of human breast cancers, and ∼50% of ductal carcinoma in situ express casein, suggesting that lineage infidelity and alveogenic mimicry may significantly contribute to early steps of breast cancer etiology. SIGNIFICANCE: Infrequently mutated genes comprise most of the mutational burden in breast tumors but are poorly understood. In vivo CRISPR screening identified functional tumor suppressors that converged on epigenetic regulation. Loss of epigenetic regulators accelerated tumorigenesis and revealed lineage infidelity and aberrant expression of alveogenesis genes as potential early events in tumorigenesis. This article is highlighted in the In This Issue feature, p. 2711.

A feed forward loop enforces YAP/TAZ signaling during tumorigenesis.

In most solid tumors, the Hippo pathway is inactivated through poorly understood mechanisms that result in the activation of the transcriptional regulators, YAP and TAZ. Here, we identify NUAK2 as a YAP/TAZ activator that directly inhibits LATS-mediated phosphorylation of YAP/TAZ and show that NUAK2 induction by YAP/TAZ and AP-1 is required for robust YAP/TAZ signaling. Pharmacological inhibition or loss of NUAK2 reduces the growth of cultured cancer cells and mammary tumors in mice. Moreover, in human patient samples, we show that NUAK2 expression is elevated in aggressive, high-grade bladder cancer and strongly correlates with a YAP/TAZ gene signature. These findings identify a positive feed forward loop in the Hippo pathway that establishes a key role for NUAK2 in enforcing the tumor-promoting activities of YAP/TAZ. Our results thus introduce a new opportunity for cancer therapeutics by delineating NUAK2 as a potential target for re-engaging the Hippo pathway.

Reciprocal stabilization of ABL and TAZ regulates osteoblastogenesis through transcription factor RUNX2.

Cellular identity in metazoan organisms is frequently established through lineage-specifying transcription factors, which control their own expression through transcriptional positive feedback, while antagonizing the developmental networks of competing lineages. Here, we have uncovered a distinct positive feedback loop that arises from the reciprocal stabilization of the tyrosine kinase ABL and the transcriptional coactivator TAZ. Moreover, we determined that this loop is required for osteoblast differentiation and embryonic skeletal formation. ABL potentiated the assembly and activation of the RUNX2-TAZ master transcription factor complex that is required for osteoblastogenesis, while antagonizing PPARγ-mediated adipogenesis. ABL also enhanced TAZ nuclear localization and the formation of the TAZ-TEAD complex that is required for osteoblast expansion. Last, we have provided genetic data showing that regulation of the ABL-TAZ amplification loop lies downstream of the adaptor protein 3BP2, which is mutated in the craniofacial dysmorphia syndrome cherubism. Our study demonstrates an interplay between ABL and TAZ that controls the mesenchymal maturation program toward the osteoblast lineage and is mechanistically distinct from the established model of lineage-specific maturation.

Analysis of Hippo and TGFß signaling in polarizing epithelial cells and mouse embryos.

The Hippo signaling pathway is involved in numerous biological events ranging from early development to organogenesis and when disrupted, impacts various human diseases including cancer. The Hippo pathway also interacts with and controls the activity of other signaling pathways such as the TGFß/Smad pathway, in which Hippo pathway activity influences the subcellular localization of Smad transcription factors. Here, we describe techniques for examining crosstalk between Hippo and TGFß signaling in polarizing mammary epithelial cells. In addition, we provide detailed methods for analyzing the subcellular localization of the Hippo pathway effectors, Taz and Yap using both in vitro cultured epithelial cells and in vivo in pregastrulation mouse embryos.

Distinct polarity cues direct Taz/Yap and TGFß receptor localization to differentially control TGFß-induced Smad signaling.

We and others have shown that the Hippo pathway effectors TAZ and YAP direct Smad activity to regulate TGFß family-induced cellular responses in stem cell and cancer biology. In polarized epithelial cells we showed that the Crumbs complex promotes Hippo-dependent cytoplasmic TAZ/YAP localization that restricts TGFß-induced Smad nuclear accumulation and activity. In this Developmental Cell issue, basal-lateral restriction of TGFß receptors is proposed as the sole mechanism suppressing Smad signaling in epithelial cells. Here we show that basal recruitment of TGFß receptors occurs subsequent to Hippo-dependent suppression of Smad activity by cytoplasmic TAZ/YAP. Our results demonstrate that receptor sequestration and Hippo control of activated Smads are distinct events regulating TGFß signaling in polarized epithelia and raise interesting questions about the function of these pathways in controlling Smad signaling in development, homeostasis, and disease. This Matters Arising Response addresses the Nallet-Staub et al. (2015) Matters Arising, published concurrently in Developmental Cell.

A role for the TGFbeta-Par6 polarity pathway in breast cancer progression.

The role of polarity signaling in cancer metastasis is ill defined. Using two three-dimensional culture models of mammary epithelial cells and an orthotopic mouse model of breast cancer, we reveal that Par6 signaling, which is regulated directly by TGFbeta, plays a role in breast cancer metastasis. Interference with Par6 signaling blocked TGFbeta-dependent loss of polarity in acini-like structures formed by non-transformed mammary cells grown in three-dimensional structures and suppressed the protrusive morphology of mesenchymal-like invasive mammary tumor cells without rescuing E-cadherin expression. Moreover, blockade of Par6 signaling in an in vivo orthotopic model of metastatic breast cancer induced the formation of ZO-1-positive epithelium-like structures in the primary tumor and suppressed metastasis to the lungs. Analysis of the pathway in tissue microarrays of human breast tumors further revealed that Par6 activation correlated with markers of the basal carcinoma subtype in BRCA1-associated tumors. These studies thus reveal a key role for polarity signaling and the control of morphologic transformation in breast cancer metastasis.

Regulation of planar cell polarity by Smurf ubiquitin ligases.

Planar cell polarity (PCP) is critical for morphogenesis in metazoans. PCP in vertebrates regulates stereocilia alignment in neurosensory cells of the cochlea and closure of the neural tube through convergence and extension movements (CE). Noncanonical Wnt morphogens regulate PCP and CE in vertebrates, but the molecular mechanisms remain unclear. Smurfs are ubiquitin ligases that regulate signaling, cell polarity and motility through spatiotemporally restricted ubiquitination of diverse substrates. Here, we report an unexpected role for Smurfs in controlling PCP and CE. Mice mutant for Smurf1 and Smurf2 display PCP defects in the cochlea and CE defects that include a failure to close the neural tube. Further, we show that Smurfs engage in a noncanonical Wnt signaling pathway that targets the core PCP protein Prickle1 for ubiquitin-mediated degradation. Our work thus uncovers ubiquitin ligases in a mechanistic link between noncanonical Wnt signaling and PCP/CE.

Sumoylation differentially regulates Goosecoid-mediated transcriptional repression.

Goosecoid (Gsc), a paired-like homeobox gene expressed in the vertebrate organizer, functions as a transcriptional repressor either by direct DNA binding to paired TAAT homeodomain sites or through recruitment by the forkhead/winged helix transcription factor Foxh1. Here, we report that Gsc is post-translationally modified by small ubiquitin-like modifier proteins (SUMO). Members of the PIAS family of proteins enhance Gsc sumoylation and this modification occurs on at least six lysine residues. Stable expression of a SUMO-defective Gsc mutant (Gsc 6Km) in MDA-MB-231 breast cancer cells results in morphological changes giving rise to cells with increased cell area. We demonstrate that Gsc 6Km can effectively repress Foxh1-mediated induction of the Mixl1 promoter, indicating that sumoylation is not required for Gsc-mediated repression of promoters where recruitment occurs through Foxh1. In contrast, Gsc 6Km exhibits a decreased ability to repress the induction of promoters to which it is directly recruited through paired-homeodomain binding sites, including its own promoter and that of the Xenopus Brachyury gene. Taken together, our data suggests that regulation of Gsc repressive activity by SUMO modification is promoter specific and may serve to differentially regulate genes that function to control cell morphology during early development and cancer.

Gab family proteins are essential for postnatal maintenance of cardiac function via neuregulin-1/ErbB signaling.

Grb2-associated binder (Gab) family of scaffolding adaptor proteins coordinate signaling cascades downstream of growth factor and cytokine receptors. In the heart, among EGF family members, neuregulin-1beta (NRG-1beta, a paracrine factor produced from endothelium) induced remarkable tyrosine phosphorylation of Gab1 and Gab2 via erythroblastic leukemia viral oncogene (ErbB) receptors. We examined the role of Gab family proteins in NRG-1beta/ErbB-mediated signal in the heart by creating cardiomyocyte-specific Gab1/Gab2 double knockout mice (DKO mice). Although DKO mice were viable, they exhibited marked ventricular dilatation and reduced contractility with aging. DKO mice showed high mortality after birth because of heart failure. In addition, we noticed remarkable endocardial fibroelastosis and increase of abnormally dilated vessels in the ventricles of DKO mice. NRG-1beta induced activation of both ERK and AKT in the hearts of control mice but not in those of DKO mice. Using DNA microarray analysis, we found that stimulation with NRG-1beta upregulated expression of an endothelium-stabilizing factor, angiopoietin 1, in the hearts of control mice but not in those of DKO mice, which accounted for the pathological abnormalities in the DKO hearts. Taken together, our observations indicated that in the NRG-1beta/ErbB signaling, Gab1 and Gab2 of the myocardium are essential for both maintenance of myocardial function and stabilization of cardiac capillary and endocardial endothelium in the postnatal heart.

Essential role for the gtfA gene encoding a putative glycosyltransferase in the adherence of Porphyromonas gingivalis.

Porphyromonas gingivalis, an oral bacterium, might play a role in the pathogenesis or progression of adult periodontitis. In this study, we isolated from P. gingivalis a putative glycosyltransferase gene, designated gtfA, which had a consensus domain for glycosyltransferase in its N terminus. GtfA consisted of 248 amino acids and its predicted molecular mass was 28 kDa; however, as the molecular mass of endogenous GtfA protein was around 40 kDa, this suggested that GtfA had undergone some posttranslational modifications. To reveal the role of the gtfA gene in P. gingivalis, we established gtfA-deficient strains by allelic replacement. Morphologically, gtfA-deficient P. gingivalis lacked mature fimbriae. gtfA-deficient P. gingivalis also showed a very low ability for autoaggregation, and its ability to attach to epithelial cells was severely impaired. Thus, the results indicate that the gtfA gene is required for P. gingivalis autoaggregation as well as attachment to epithelial cells. These results suggest that GtfA might have an important role in the pathogenicity of P. gingivalis by regulating adhesion.

Effects of chlorhexidine, minocycline, and metronidazole on Porphyromonas gingivalis strain 381 in biofilms.

BACKGROUND: Porphyromonas gingivalis is found in subgingival biofilm and is associated with periodontal disease. Bacteria in biofilms are able to resist higher antimicrobial concentrations than in suspension. Little is known about the susceptibility of P. gingivalis in biofilms to antimicrobial agents. The effects of chlorhexidine gluconate, minocycline hydrochloride, and metronidazole on P. gingivalis biofilms were examined in vitro. METHODS: P. gingivalis strain 381 biofilms were prepared on 32 hydroxyapatite disks. At 0, 24, 72, and 144 hours after perfusion of the three antimicrobial agents, two disks from each device were used to assess the antimicrobial effects by adenosine triphosphate (ATP) bioluminescence, and for morphological investigation by scanning electron microscopy (SEM). RESULTS: Close relationships were found between the results of the ATP analyses and the SEM observations in all groups examined. A significant decrease (P < 0.001) in ATP content was found between the chlorhexidine-treated and control groups. The extracellular matrix structure and P. gingivalis cells were altered in the presence of chlorhexidine. Minocycline hydrochloride also caused a decrease (P < 0.05) in the ATP content and morphological change on P. gingivalis biofilms. Metronidazole showed no significant efficacy against P. gingivalis biofilms. CONCLUSION: Chlorhexidine gluconate was effective at reducing the viability of P. gingivalis 381 cells in biofilms, while minocycline hydrochloride and metronidazole exhibited weaker effects.

Adapter molecule Grb2-associated binder 1 is specifically expressed in marginal zone B cells and negatively regulates thymus-independent antigen-2 responses.

Grb2-associated binder 1 (Gab1) is a member of the Gab/daughter of sevenless family of adapter molecules involved in the signal transduction pathways of a variety of growth factors, cytokines, and Ag receptors. To know the role for Gab1 in hematopoiesis and immune responses in vivo, we analyzed radiation chimeras reconstituted with fetal liver (FL) cells of Gab1(-/-) mice, because Gab1(-/-) mice are lethal to embryos. Transfer of Gab1(-/-) FL cells of 14.5 days post-coitum rescued lethally irradiated mice, indicating that Gab1 is not essential for hematopoiesis. Although mature T and B cell subsets developed normally in the peripheral lymphoid organs, reduction of pre-B cells and increase of myeloid cells in the Gab1(-/-) FL chimeras suggested the regulatory roles for Gab1 in hematopoiesis. The chimera showed augmented IgM and IgG1 production to thymus-independent (TI)-2 Ag, although they showed normal responses for thymus-dependent and TI-1 Ags, indicating its negative role specific to TI-2 response. Gab1(-/-) splenic B cells stimulated with anti-delta-dextran plus IL-4 plus IL-5 showed augmented IgM and IgG1 production in vitro that was corrected by the retrovirus-mediated transfection of the wild-type Gab1 gene, clearly demonstrating the cell-autonomous, negative role of Gab1. Furthermore, we showed that the negative role of Gab1 required its Src homology 2-containing tyrosine phosphatase-2 binding sites. Cell fractionation analysis revealed that nonfollicular B cells were responsible for the augmented Ab production in vitro. Consistent with these results, the Gab1 gene was expressed in marginal zone B cells but not follicular B cells. These results indicated that Gab1 is a unique negative regulator specific for TI-2 responses.

Requirement of Gab2 for mast cell development and KitL/c-Kit signaling.

Mast cells are thought to participate in a variety of immune responses, such as parasite resistance and the allergic reaction. Mast cell development depends on stem cell factor (Kit ligand) and its receptor, c-Kit. Gab2 is an adaptor molecule containing a pleckstrin homology domain and potential binding sites for SH2 and SH3 domains. Gab2 is phosphorylated on tyrosine after stimulation with cytokines and growth factors, including KitL. Gab2-deficient mice were created to define the physiological requirement for Gab2 in KitL/c-Kit signaling and mast cell development. In Gab2-deficient mice, the number of mast cells was reduced markedly in the stomach and less severely in the skin. Bone marrow-derived mast cells (BMMCs) from the Gab2-deficient mice grew poorly in response to KitL. KitL-induced ERK MAP kinase and Akt activation were impaired in Gab2-deficient BMMCs. These data indicate that Gab2 is required for mast cell development and KitL/c-Kit signaling.