Exploring the prognostic significance of arm-level copy number alterations in triple-negative breast cancer.

Somatic copy number alterations (SCNAs) are prevalent in cancer and play a significant role in both tumorigenesis and therapeutic resistance. While focal SCNAs have been extensively studied, the impact of larger arm-level SCNAs remains poorly understood. Here, we investigated the association between arm-level SCNAs and overall survival in triple-negative breast cancer (TNBC), an aggressive subtype of breast cancer lacking targeted therapies. We identified frequent arm-level SCNAs, including 21q gain and 7p gain, which correlated with poor overall survival in TNBC patients. Further, we identified the expression of specific genes within these SCNAs associated with survival. Notably, we found that the expression of RIPK4, a gene located on 21q, exhibited a strong correlation with poor overall survival. In functional assays, we demonstrated that targeting Ripk4 in a murine lung metastatic TNBC model significantly reduced tumor burden, improved survival, and increased CD4+ and CD8+ T cell infiltration. RIPK4 enhanced the survival of triple-negative breast cancer cells at secondary sites, thereby facilitating the formation of metastatic lesions. Our findings highlight the significance of arm-level SCNAs in breast cancer progression and identify RIPK4 as a putative driver of TNBC metastasis and immunosuppression.

Cotargeting CDK4/6 and BRD4 Promotes Senescence and Ferroptosis Sensitivity in Cancer.

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors are approved for breast cancer treatment and show activity against other malignancies, including KRAS-mutant non-small cell lung cancer (NSCLC). However, the clinical efficacy of CDK4/6 inhibitors is limited due to frequent drug resistance and their largely cytostatic effects. Through a genome-wide cDNA screen, we identified that bromodomain-containing protein 4 (BRD4) overexpression conferred resistance to the CDK4/6 inhibitor palbociclib in KRAS-mutant NSCLC cells. Inhibition of BRD4, either by RNA interference or small-molecule inhibitors, synergized with palbociclib to induce senescence in NSCLC cells and tumors, and the combination prolonged survival in a KRAS-mutant NSCLC mouse model. Mechanistically, BRD4-inhibition enhanced cell-cycle arrest and reactive oxygen species (ROS) accumulation, both of which are necessary for senescence induction; this in turn elevated GPX4, a peroxidase that suppresses ROS-triggered ferroptosis. Consequently, GPX4 inhibitor treatment selectively induced ferroptotic cell death in the senescent cancer cells, resulting in tumor regression. Cotargeting CDK4/6 and BRD4 also promoted senescence and ferroptosis vulnerability in pancreatic and breast cancer cells. Together, these findings reveal therapeutic vulnerabilities and effective combinations to enhance the clinical utility of CDK4/6 inhibitors. SIGNIFICANCE: The combination of cytostatic CDK4/6 and BRD4 inhibitors induces senescent cancer cells that are primed for activation of ferroptotic cell death by targeting GPX4, providing an effective strategy for treating cancer.

Obesity alters monocyte developmental trajectories to enhance metastasis.

Obesity is characterized by chronic systemic inflammation and enhances cancer metastasis and mortality. Obesity promotes breast cancer metastasis to lung in a neutrophil-dependent manner; however, the upstream regulatory mechanisms of this process remain unknown. Here, we show that obesity-induced monocytes underlie neutrophil activation and breast cancer lung metastasis. Using mass cytometry, obesity favors the expansion of myeloid lineages while restricting lymphoid cells within the peripheral blood. RNA sequencing and flow cytometry revealed that obesity-associated monocytes resemble professional antigen-presenting cells due to a shift in their development and exhibit enhanced MHCII expression and CXCL2 production. Monocyte induction of the CXCL2-CXCR2 axis underlies neutrophil activation and release of neutrophil extracellular traps to promote metastasis, and enhancement of this signaling axis is observed in lung metastases from obese cancer patients. Our findings provide mechanistic insight into the relationship between obesity and cancer by broadening our understanding of the interactive role that myeloid cells play in this process.

Single-cell spatial landscape of immunotherapy response reveals mechanisms of CXCL13 enhanced antitumor immunity.

BACKGROUND: Immunotherapy has revolutionized clinical outcomes for patients suffering from lung cancer, yet relatively few patients sustain long-term durable responses. Recent studies have demonstrated that the tumor immune microenvironment fosters tumorous heterogeneity and mediates both disease progression and response to immune checkpoint inhibitors (ICI). As such, there is an unmet need to elucidate the spatially defined single-cell landscape of the lung cancer microenvironment to understand the mechanisms of disease progression and identify biomarkers of response to ICI. METHODS: Here, in this study, we applied imaging mass cytometry to characterize the tumor and immunological landscape of immunotherapy response in non-small cell lung cancer by describing activated cell states, cellular interactions and neighborhoods associated with improved efficacy. We functionally validated our findings using preclinical mouse models of cancer treated with anti-programmed cell death protein-1 (PD-1) immune checkpoint blockade. RESULTS: We resolved 114,524 single cells in 27 patients treated with ICI, enabling spatial resolution of immune lineages and activation states with distinct clinical outcomes. We demonstrated that CXCL13 expression is associated with ICI efficacy in patients, and that recombinant CXCL13 potentiates anti-PD-1 response in vivo in association with increased antigen experienced T cell subsets and reduced CCR2+ monocytes. DISCUSSION: Our results provide a high-resolution molecular resource and illustrate the importance of major immune lineages as well as their functional substates in understanding the role of the tumor immune microenvironment in response to ICIs.

Neutrophil oxidative stress mediates obesity-associated vascular dysfunction and metastatic transmigration.

Metastasis is the leading cause of cancer-related deaths, and obesity is associated with increased breast cancer (BC) metastasis. Preclinical studies have shown that obese adipose tissue induces lung neutrophilia associated with enhanced BC metastasis to this site. Here we show that obesity leads to neutrophil-dependent impairment of vascular integrity through loss of endothelial adhesions, enabling cancer cell extravasation into the lung. Mechanistically, neutrophil-produced reactive oxygen species in obese mice increase neutrophil extracellular DNA traps (NETs) and weaken endothelial junctions, facilitating the influx of tumor cells from the peripheral circulation. In vivo treatment with catalase, NET inhibitors or genetic deletion of Nos2 reversed this effect in preclinical models of obesity. Imaging mass cytometry of lung metastasis samples from patients with cancer revealed an enrichment in neutrophils with low catalase levels correlating with elevated body mass index. Our data provide insights into potentially targetable mechanisms that underlie the progression of BC in the obese population.

Myosin II in Cancer Cells Shapes the Immune Microenvironment.

Tumor migration is driven by actomyosin contractility. A recent publication by Georgouli et al. (Cell 2019;176:757-774) describes how crosstalk between the cell migration machinery and tumor-associated macrophages (TAMs) shapes the microenvironment to promote tumor growth. Indirectly targeting TAMs by inhibiting the motility of tumor cells could hinder metastatic spread.

EphA2 signaling is impacted by carcinoembryonic antigen cell adhesion molecule 1-L expression in colorectal cancer liver metastasis in a cell context-dependent manner.

We have shown that carcinoembryonic antigen cell adhesion molecule 1 long isoform (CEACAM1-L) expression in MC38 metastatic colorectal cancer (CRC) cells results in liver metastasis inhibition via CCL2 and STAT3 signaling. But other molecular mechanisms orchestrating CEACAM1-L-mediated metastasis inhibition remain to be defined. We screened a panel of mouse and human CRC cells and evaluated their metastatic outcome after CEACAM1 overexpression or downregulation. An unbiased transcript profiling and a phospho-receptor tyrosine kinase screen comparing MC38 CEACAM1-L-expressing and non-expressing (CT) CRC cells revealed reduced ephrin type-A receptor 2 (EPHA2) expression and activity. An EPHA2-specific inhibitor reduced EPHA2 downstream signaling in CT cells similar to that in CEACAM1-L cells with decreased proliferation and migration. Human CRC patients exhibiting high CEACAM1 in combination with low EPHA2 expression benefited from longer time to first recurrence/metastasis compared to those with high EPHA2 expression. With the added interaction of CEACAM6, we denoted that CEACAM1 high- and EPHA2 low-expressing patient samples with lower CEACAM6 expression also exhibited a longer time to first recurrence/metastasis. In HT29 human CRC cells, down-regulation of CEACAM1 along with CEA and CEACAM6 up-regulation led to higher metastatic burden. Overall, CEACAM1-L expression in poorly differentiated CRC can inhibit liver metastasis through cell context-dependent EPHA2-mediated signaling. However, CEACAM1's role should be considered in the presence of other CEACAM family members.

Carcinoembryonic Antigen Cell Adhesion Molecule 1 long isoform modulates malignancy of poorly differentiated colon cancer cells.

OBJECTIVE: Nearly 20%-29% of patients with colorectal cancer (CRC) succumb to liver or lung metastasis and there is a dire need for novel targets to improve the survival of patients with metastasis. The long isoform of the Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1-L or CC1-L) is a key regulator of immune surveillance in primary CRC, but its role in metastasis remains largely unexplored. We have examined how CC1-L expression impacts on colon cancer liver metastasis. DESIGN: Murine MC38 transfected with CC1-L were evaluated in vitro for proliferation, migration and invasion, and for in vivo experimental liver metastasis. Using shRNA silencing or pharmacological inhibition, we delineated the role in liver metastasis of Chemokine (C-C motif) Ligand 2 (CCL2) and Signal Transducer and Activator of Transcription 3 (STAT3) downstream of CC1-L. We further assessed the clinical relevance of these findings in a cohort of patients with CRC. RESULTS: MC38-CC1-L-expressing cells exhibited significantly reduced in vivo liver metastasis and displayed decreased CCL2 chemokine secretion and reduced STAT3 activity. Down-modulation of CCL2 expression and pharmacological inhibition of STAT3 activity in MC38 cells led to reduced cell invasion capacity and decreased liver metastasis. The clinical relevance of our findings is illustrated by the fact that high CC1 expression in patients with CRC combined with some inflammation-regulated and STAT3-regulated genes correlate with improved 10-year survival. CONCLUSIONS: CC1-L regulates inflammation and STAT3 signalling and contributes to the maintenance of a less-invasive CRC metastatic phenotype of poorly differentiated carcinomas.

The Nlrp3 Inflammasome Suppresses Colorectal Cancer Metastatic Growth in the Liver by Promoting Natural Killer Cell Tumoricidal Activity.

The crosstalk between inflammation and tumorigenesis is now clearly established. However, how inflammation is elicited in the metastatic environment and the corresponding contribution of innate immunity pathways in suppressing tumor growth at secondary sites are poorly understood. Here, we show that mice deficient in Nlrp3 inflammasome components had exacerbated liver colorectal cancer metastatic growth, which was mediated by impaired interleukin-18 (IL-18) signaling. Control of tumor growth was independent of differential cancer cell colonization or proliferation, intestinal microbiota effects, or tumoricidal activity by the adaptive immune system. Instead, the inflammasome-IL-18 pathway impacted maturation of hepatic NK cells, surface expression of the death ligand FasL, and capacity to kill FasL-sensitive tumors. Our results define a regulatory signaling circuit within the innate immune system linking inflammasome activation to effective NK-cell-mediated tumor attack required to suppress colorectal cancer growth in the liver.

Carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) in cancer progression and metastasis.

The discovery of the carcinoembryonic antigen (CEA) as a tumor marker for colorectal cancer some 50 years ago became the first step in the identification of a much larger family of 12 carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) with surprisingly diverse functions in cell adhesion, in intracellular and intercellular signaling, and during complex biological processes such as cancer progression, inflammation, angiogenesis, and metastasis. The development of proper molecular and biochemical tools and mouse models has enabled bidirectional translation of the CEACAM network biology. Indeed, CEACAM1, CEACAM5, and CEACAM6 are now considered valid clinical biomarkers and promising therapeutic targets in melanoma, lung, colorectal, and pancreatic cancers. These fascinating proteins illustrate how a better understanding of the CEACAM family of cell adhesion molecules reveals their functional link to the underlying disease and lead to new monitoring and targeting opportunities.

Stromal CEACAM1 expression regulates colorectal cancer metastasis.

Colorectal cancer metastasis to Ceacam1-/- livers is significantly impaired, compared with wild type livers, due to decreased endothelial cell survival, reduced tumor cell proliferation, diminished immune infiltration and altered chemokine expression. Ceacam1-/- myeloid-derived suppressor cells diminish metastatic burden, as confirmed by bone marrow transplantation and adoptive transfer experiments.

CEACAM1 deficiency delays important wound healing processes.

Cutaneous wound healing is a complex process that requires the coordination of many cell types to achieve proper tissue repair. Four major overlapping processes have been identified in wound healing: hemostasis, inflammation, reepithelialization and granulation tissue formation, and tissue remodeling. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a glycoprotein expressed in epithelial, endothelial, lymphoid, and myeloid cells. Given its known roles in angiogenesis, cell migration, and immune functions, we hypothesized that CEACAM1 might also be involved in cutaneous wound healing and that a number of relevant CEACAM1-positive cell types might contribute to wound healing. To evaluate the role of CEACAM1 in these processes, 6-mm-diameter skin wounds were inflicted on Ceacam1(-/-) and wild-type mice. Herein, we demonstrate that CEACAM1 deletion indeed affects wound healing in three key ways. Infiltration of F4/80(+) macrophages was decreased in Ceacam1(-/-) wounds, altering inflammatory processes. Reepithelialization in Ceacam1(-/-) wounds was delayed. Furthermore, the vascular density of the granulation tissue in Ceacam1(-/-) wounds was significantly diminished. These results confirm CEACAM1's role as an important regulator of key processes in cutaneous wound healing, although whether this works via a specific cell type or alterations in the functioning of multiple processes remains to be determined.

Re-assessing K15 as an epidermal stem cell marker.

The intermediate filament keratin 15 (K15) is present in variable amounts in various stratified epithelia, but has also been reported to be a stem cell marker in the hair follicle. Using peptide specific antibodies, we evaluated the temporal and spatial distribution pattern of K15 expression/localization during normal epidermal development and initiation of hair follicle formation, and in the injured mature epidermis (e.g., during acute injury and repair and in tumorigenesis). During development, K15 expression is first localized to a subset of epidermal basal cells and the overlying periderm at E12.5, but its expression is seen throughout the basal layer by E15.5 and beyond. In hair follicle morphogenesis, initial peg formation occurs in a K15-null area at E14.5 and as peg elongation proceeds through to the mature hair follicle, K15 expression follows the leading edge with positive cells restricted to the outer root sheath. In an epidermal injury model, K15 is first up-regulated and associated with both the basal and suprabasal layers of the interfollicular epidermis then expression becomes sporadic and down-regulated before a basal layer-specific association is re-established in the repaired epidermis. During tumorigenesis, K15 is first mis-expressed, and is ultimately down-regulated. Our data suggest that K15 protein expression may reflect not only expression in a stem or progenitor cell subpopulation, but also reflects the activity and responsiveness of basal-like cells to loss of homeostasis of the epidermal differentiation program. Thus, the data suggest caution in using K15 alone to delineate epidermal stem cells, and underscore the need for further investigation of K15 and other markers in epidermal cell subpopulations.

Involucrin-claudin-6 tail deletion mutant (CDelta206) transgenic mice: a model of delayed epidermal permeability barrier formation and repair.

Preterm birth is a major global health problem that results in a large number of infant deaths, many of which are attributable to the complications of an immature epidermal permeability barrier (EPB), for which there is currently no effective therapeutic option. The mammalian EPB is formed during development and is essential for survival as it maintains thermoregulation and hydration, and provides a defense against infection. Using transgenic mouse technology, we have demonstrated the importance of claudin (Cldn)-containing tight junctions (TJs) in epidermal differentiation and, in particular, that epidermal suprabasal overexpression of Cldn6 results in an EPB-deficient phenotype that phenocopies the dysfunctional EPB of premature human infants. In this study, we used the same approach to target a Cldn6 tail deletion mutant to the epidermis of mice [involucrin (Inv)-Cldn6-CDelta206 transgenic mice]. The Inv-Cldn6-CDelta206 transgenic mice displayed a developmental delay in EPB formation, as shown by the expression of keratins and Cldns, and by X-Gal penetration assays. Trans-epidermal water loss measurements and immunolocalization studies indicated that the epidermal differentiation program was also perturbed in postnatal Inv-Cldn6-CDelta206 transgenic mice resulting in a delayed maturation. Notably, however, expression/localization of epidermal differentiation and maturation markers, including Cldns, indicated that the transgenic epidermis matured and normalized by postnatal day 10, which is 3 days after the wild-type epidermis. Our results suggest that activation of the extracellular signal-regulated kinase 1/2 (Erk1/2) pathway and Cldn1 phosphorylation are associated with the repair and maturation of the skin barrier processes. These studies provide additional support for the crucial role of Cldns in epidermal differentiation, maturation and the formation of the EPB, and describe a novel animal model for evaluating postnatal epidermal maturation and therapies that may accelerate the process.

Dermatitis and aging-related barrier dysfunction in transgenic mice overexpressing an epidermal-targeted claudin 6 tail deletion mutant.

The barrier function of the skin protects the mammalian body against infection, dehydration, UV irradiation and temperature fluctuation. Barrier function is reduced with the skin's intrinsic aging process, however the molecular mechanisms involved are unknown. We previously demonstrated that Claudin (Cldn)-containing tight junctions (TJs) are essential in the development of the epidermis and that transgenic mice overexpressing Cldn6 in the suprabasal layers of the epidermis undergo a perturbed terminal differentiation program characterized in part by reduced barrier function. To dissect further the mechanisms by which Cldn6 acts during epithelial differentiation, we overexpressed a Cldn6 cytoplasmic tail deletion mutant in the suprabasal compartment of the transgenic mouse epidermis. Although there were no gross phenotypic abnormalities at birth, subtle epidermal anomalies were present that disappeared by one month of age, indicative of a robust injury response. However, with aging, epidermal changes with eventual chronic dermatitis appeared with a concomitant barrier dysfunction manifested in increased trans-epidermal water loss. Immunohistochemical analysis revealed aberrant suprabasal Cldn localization with marked down-regulation of Cldn1. Both the proliferative and terminal differentiation compartments were perturbed as evidenced by mislocalization of multiple epidermal markers. These results suggest that the normally robust injury response mechanism of the epidermis is lost in the aging Involucrin-Cldn6-CDelta196 transgenic epidermis, and provide a model for evaluation of aging-related skin changes.

Insights into the role of the calcium sensing receptor in epidermal differentiation in vivo.

While the important role of calcium (Ca(++)) signaling is fundamental in epidermal cell physiology, a detailed knowledge of precisely how epidermal cells respond to Ca(++) levels is not clear. Using peptide-specific antibodies that we generated, we set out to evaluate the temporal and spatial distribution pattern of the Ca(++)-sensing receptor (CaSR) during epidermogenesis and to assess its involvement in the mature epidermis (e.g., in acute injury and tumorigenesis). Our data indicate a developmentally regulated expression of CaSR: up-regulation occurs in specific epidermal cells and cell layers in normal development or in response to injury when epidermal cells are induced to undergo commitment and early differentiation events, and down-regulation occurs in terminal differentiation stages. These results provide a new perspective on the role of the CaSR in these processes and describe a novel tool for evaluating Ca(++)-mediated epidermal differentiation.

Immunohistochemistry on paraffin sections of mouse epidermis using fluorescent antibodies.

In the epidermis, immunohistochemistry is an efficient means of localizing specific proteins to their relative expression compartment; namely the basal, suprabasal, and stratum corneum layers. The precise localization within the epidermis of a particular protein lends clues toward its functional role within the epidermis. In this chapter, we describe a reliable method for immunolocalization within the epidermis modified for both frozen and paraffin sections that we use very routinely in our laboratory. Paraffin sections generally provide much better morphology, hence, superior results and photographs; however, not all antibodies will work with the harsh fixation and treatment involved in their processing. Therefore, the protocol for frozen sectioning is also included. Within paraffin sectioning, two fixation protocols are described (Bouin's and paraformaldehyde); the choice of fixative will be directly related to the antibody specifications and may require another fixing method.

Changes in the distribution pattern of Claudin tight junction proteins during the progression of mouse skin tumorigenesis.

BACKGROUND: Despite the fact that morphological and physiological observations suggest that the tight junction (TJ)-based permeability barrier is modified/disrupted in tumorigenesis, the role of members of the Claudin (Cldn) family of TJ proteins is not well-understood. Using a well-established two-stage chemical carcinogenesis model, we investigated the temporal and spatial changes in expression of those Cldns that we have previously demonstrated to be important in epidermal differentiation and the formation of the epidermal permeability barrier, i.e., Cldn1, Cldn6, Cldn11, Cldn12 and Cldn18. METHODS: The lower dorsal backskin of mice was treated topically with 7,12-dimethylbenz(a)anthracene (DMBA; 0.25 mg/ml in acetone) and following a 10-day incubation period, 12-O-tetradecanoyl-phorbol-13-acetate (TPA; 25 microg/ml in acetone) was applied three times a week to the same area. Backskin samples were dissected 2, 4, 6, 8 and 12 weeks after the initiation of the experimental protocol and immunohistochemistry was performed on sections using antibodies against the following: Cldn1, Cldn6, Cldn11, Cldn12, Cldn18, Ki67 and CD3. RESULTS: Our data indicate that along with the changes in epidermal cell morphology and differentiation that occur during tumor formation, there is a dramatic change in Cldn distribution consistent with cell polarity and barrier selectivity changes. Specifically, in the early stages of DMBA/TPA treatment, the suprabasal-specific Cldns occupy an expanded zone of expression corresponding to an increased number of suprabasal epidermal cell layers. As tumorigenesis progressed, the number of suprabasal epidermal layers positive for Cldn6, Cldn11, Cldn12 and Cldn18 was reduced, especially in the lower strata of the expanded suprabasal zone. In addition, a variably reduced cell membrane association of those differentiation-specific Cldns was observed, especially within the infiltrating epidermal structures. In contrast, Cldn1 (which is normally expressed in all the living layers of the epidermis) remained restricted to the cell membrane throughout the tumorigenesis protocol. However commencing 2 weeks after treatment there was a marked decrease in the number of Cldn1-positive basal cells, and the zone of Cldn1-null epidermal cells was expanded up into the lower stratified epidermis throughout the progression of DMBA/TPA treatment. In addition, there was no Cldn1 localization in the infiltrating epidermal structures of the tumorigenic epidermis. CONCLUSION: This is the first demonstration of the changes in Cldn expression in the progression of DMBA/TPA-induced skin tumors; however further investigation into the molecular mechanisms regulating the observed changes in barrier selectivity during tumorigenesis is required.

Claudin immunolocalization in neonatal mouse epithelial tissues.

Emerging evidence supports the notion that claudins (Cldns) are dynamically regulated under normal conditions to respond to the selective permeability requirements of various tissues, and that their expression is developmentally controlled. We describe the localization of those Cldns that we have previously demonstrated to be functionally important in epidermal differentiation and the formation of the epidermal permeability barrier, e.g., Cldn1, Cldn6, Cldn11, and Cldn18, and the presence of Cldn3 and Cldn5 in various neonatal mouse epithelia including the epidermis, nail, oral mucosa, tongue, and stomach. Cldn1 is localized in the differentiated and/or undifferentiated compartments of the epidermis and nail and in the dorsal surface of the tongue and glandular compartment of the stomach but is absent from the oral mucosa and the keratinized compartment of the stomach. Cldn3 is present in the basal cells of the nail matrix and both compartments of the murine stomach but not in the epidermis, oral mucosa, or tongue. Cldn5 is found in the glandular compartment of the stomach but not in the epidermis, nail unit, oral mucosa, forestomach, and tongue. Cldn6, Cldn11, and Cldn18 occur in the differentiating suprabasal compartment of the epidermis, nail, and oral mucosa and in the dorsal and ventral surfaces of the tongue and the keratinized squamous epithelium of the stomach. The simple columnar epithelium of the glandular stomach stains for Cldn18 and reveals a non-membranous pattern for Cldn6 and Cldn11 expression. Our results demonstrate differential Cldn protein profiles in various epithelial tissues and their differentiation stages. Although the molecular mechanisms regulating Cldn expression are unknown, elucidation of their differential localization patterns in tissues with diverse permeability requirements should provide a better understanding of the role of tight junctions in tissue function.