Diving into broad-scale and high-resolution population genomics to decipher drivers of structure and climatic vulnerability in a marine invertebrate.

Species with widespread distributions play a crucial role in our understanding of climate change impacts on population structure. In marine species, population structure is often governed by both high connectivity potential and selection across strong environmental gradients. Despite the complexity of factors influencing marine populations, studying species with broad distribution can provide valuable insights into the relative importance of these factors and the consequences of climate-induced alterations across environmental gradients. We used the northern shrimp Pandalus borealis and its wide latitudinal distribution to identify current drivers of population structure and predict the species' vulnerability to climate change. A total of 1514 individuals sampled across 24° latitude were genotyped at high geographic (54 stations) and genetic (14,331 SNPs) resolutions to assess genetic variation and environmental correlations. Four populations were identified in addition to finer substructure associated with local adaptation. Geographic patterns of neutral population structure reflected predominant oceanographic currents, while a significant proportion of the genetic variation was associated with gradients in salinity and temperature. Adaptive landscapes generated using climate projections suggest a larger genomic offset in the southern extent of the P. borealis range, where shrimp had the largest adaptive standing genetic variation. Our genomic results combined with recent observations point to further deterioration in southern regions and an impending vulnerable status in the regions at higher latitudes for P. borealis. They also provide rare insights into the drivers of population structure and climatic vulnerability of a widespread meroplanktonic species, which is crucial to understanding future challenges associated with invertebrates essential to ecosystem functioning.

Northern shrimp from multiple origins show similar sensitivity to global change drivers, but different cellular energetic capacity.

Species with a wide distribution can experience significant regional variation in environmental conditions, to which they can acclimatize or adapt. Consequently, the geographic origin of an organism can influence its responses to environmental changes, and therefore its sensitivity to combined global change drivers. This study aimed at determining the physiological responses of the northern shrimp, Pandalus borealis, at different levels of biological organization and from four different geographic origins, exposed to elevated temperature and low pH to define its sensitivity to future ocean warming and acidification. Shrimp sampled within the northwest Atlantic were exposed for 30 days to combinations of three temperature (2, 6 or 10°C) and two pH levels (7.75 or 7.40). Survival, metabolic rates, whole-organism aerobic performance and cellular energetic capacity were assessed at the end of the exposure. Our results show that shrimp survival was negatively affected by temperature above 6°C and low pH, regardless of their origin. Additionally, shrimp from different origins show overall similar whole-organism performances: aerobic scope increasing with increasing temperature and decreasing with decreasing pH. Finally, the stability of aerobic metabolism appears to be related to cellular adjustments specific to shrimp origin. Our results show that the level of intraspecific variation differs among levels of biological organization: different cellular capacities lead to similar individual performances. Thus, the sensitivity of the northern shrimp to ocean warming and acidification is overall comparable among origins. Nonetheless, shrimp vulnerability to predicted global change scenarios for 2100 could differ among origins owing to different regional environmental conditions.

Direct visualization of emergent metastatic features within an ex vivo model of the tumor microenvironment.

Preventing tumor cells from acquiring metastatic properties would significantly reduce cancer mortality. However, due to the complex nature of this process, it remains one of the most poorly understood and untreatable aspects of cancer. Ischemia and hypoxia in solid tumors are requisite in metastasis formation -- conditions that arise far from functional blood vessels and deep within tumor tissues. These secluded locations impede the observation of pre-metastatic tumor cells and their interactions with stromal cells, which are also critical in the initiation of this process. Thus, the initiation of metastasis has been incredibly difficult to model in the lab and to observe in vivo. We present an ex vivo model of the tumor microenvironment, called 3MIC, which overcomes these experimental challenges and enables the observation of ischemic tumor cells in their native 3D context with high spatial and temporal resolutions. The 3MIC recreates ischemic conditions in the tumor microenvironment and facilitates the co-culture of different cell types. Using live microscopy, we showed that ischemia, but not hypoxia alone, increases the motility and invasive properties of cells derived from primary tumors. These changes are phenotypic and can occur without clonal selection. We directly observed how interactions with stromal cells such as macrophages increased tumor invasion in conjunction with the effects of an ischemic microenvironment. Finally, we tested the effects of chemotherapy drugs under different metabolic microenvironments and found that ischemic tumor cells are more resistant to paclitaxel, possibly due to a metabolic resistance mechanism. Overall, the 3MIC is a cost-effective system that allows for the dissection of the complexity of the tumor microenvironment and direct observation of the emergence of metastasis, as well as the testing of treatments that may halt this process.

Hypoxia Potentiates the Inflammatory Fibroblast Phenotype Promoted by Pancreatic Cancer Cell-Derived Cytokines.

Cancer-associated fibroblasts (CAF) are a major cell type in the stroma of solid tumors and can exert both tumor-promoting and tumor-restraining functions. CAF heterogeneity is frequently observed in pancreatic ductal adenocarcinoma (PDAC), a tumor characterized by a dense and hypoxic stroma that features myofibroblastic CAFs (myCAF) and inflammatory CAFs (iCAF) that are thought to have opposing roles in tumor progression. While CAF heterogeneity can be driven in part by tumor cell-produced cytokines, other determinants shaping CAF identity and function are largely unknown. In vivo, we found that iCAFs displayed a hypoxic gene expression and biochemical profile and were enriched in hypoxic regions of PDAC tumors, while myCAFs were excluded from these regions. Hypoxia led fibroblasts to acquire an inflammatory gene expression signature and synergized with cancer cell-derived cytokines to promote an iCAF phenotype in a HIF1α-dependent fashion. Furthermore, HIF1α stabilization was sufficient to induce an iCAF phenotype in stromal cells introduced into PDAC organoid cocultures and to promote PDAC tumor growth. These findings indicate hypoxia-induced HIF1α as a regulator of CAF heterogeneity and promoter of tumor progression in PDAC. SIGNIFICANCE: Hypoxia in the tumor microenvironment of pancreatic cancer potentiates the cytokine-induced inflammatory CAF phenotype and promotes tumor growth. See related commentary by Fuentes and Taniguchi, p. 1560.

A Complex and Evolutive Character: Two Face Aspects of ECM in Tumor Progression.

Tumor microenvironment, including extracellular matrix (ECM) and stromal cells, is a key player during tumor development, from initiation, growth and progression to metastasis. During all of these steps, remodeling of matrix components occurs, changing its biochemical and physical properties. The global and basic cancer ECM model is that tumors are surrounded by activated stromal cells, that remodel physiological ECM to evolve into a stiffer and more crosslinked ECM than in normal conditions, thereby increasing invasive capacities of cancer cells. In this review, we show that this too simple model does not consider the complexity, specificity and heterogeneity of each organ and tumor. First, we describe the general ECM in context of cancer. Then, we go through five invasive and most frequent cancers from different origins (breast, liver, pancreas, colon, and skin), and show that each cancer has its own specific matrix, with different stromal cells, ECM components, biochemical properties and activated signaling pathways. Furthermore, in these five cancers, we describe the dual role of tumor ECM: as a protective barrier against tumor cell proliferation and invasion, and as a major player in tumor progression. Indeed, crosstalk between tumor and stromal cells induce changes in matrix organization by remodeling ECM through invadosome formation in order to degrade it, promoting tumor progression and cell invasion. To sum up, in this review, we highlight the specificities of matrix composition in five cancers and the necessity not to consider the ECM as one general and simple entity, but one complex, dynamic and specific entity for each cancer type and subtype.

Linking Matrix Rigidity with EMT and Cancer Invasion.

The extracellular matrix (ECM) plays a major role in cancer progression through its increased deposition and alignment. In this issue of Developmental Cell, Fattet et al. reveal a pathway in which ECM stiffness promotes EPHA2/LYN complex activation, leading to TWIST1 nuclear localization and triggering EMT in breast cancer.

ER-resident oxidoreductases are glycosylated and trafficked to the cell surface to promote matrix degradation by tumour cells.

Tumour growth and invasiveness require extracellular matrix (ECM) degradation and are stimulated by the GALA pathway, which induces protein O-glycosylation in the endoplasmic reticulum (ER). ECM degradation requires metalloproteases, but whether other enzymes are required is unclear. Here, we show that GALA induces the glycosylation of the ER-resident calnexin (Cnx) in breast and liver cancer. Glycosylated Cnx and its partner ERp57 are trafficked to invadosomes, which are sites of ECM degradation. We find that disulfide bridges are abundant in connective and liver ECM. Cell surface Cnx-ERp57 complexes reduce these extracellular disulfide bonds and are essential for ECM degradation. In vivo, liver cancer cells but not hepatocytes display cell surface Cnx. Liver tumour growth and lung metastasis of breast and liver cancer cells are inhibited by anti-Cnx antibodies. These findings uncover a moonlighting function of Cnx-ERp57 at the cell surface that is essential for ECM breakdown and tumour development.

Multitasking discoidin domain receptors are involved in several and specific hallmarks of cancer.

Discoidin domain receptors, DDR1 and DDR2, are two members of collagen receptor family that belong to tyrosine kinase receptor subgroup. Unlike other matrix receptor-like integrins, these collagen receptors have not been extensively studied. However, more and more studies are focusing on their involvement in cancer. These two receptors are present in several subcellular localizations such as intercellular junction or along type I collagen fibers. Consequently, they are involved in multiple cellular functions, for instance, cell cohesion, proliferation, adhesion, migration and invasion. Furthermore, various signaling pathways are associated with these multiple functions. In this review, we highlight and characterize hallmarks of cancer in which DDRs play crucial roles. We discuss recent data from studies that demonstrate the involvement of DDRs in tumor proliferation, cancer mutations, drug resistance, inflammation, neo-angiogenesis and metastasis. DDRs could be potential targets in cancer and we conclude this review by discussing the different ways to inhibits them.

Organelle Specific O-Glycosylation Drives MMP14 Activation, Tumor Growth, and Metastasis.

Cancers grow within tissues through molecular mechanisms still unclear. Invasiveness correlates with perturbed O-glycosylation, a covalent modification of cell-surface proteins. Here, we show that, in human and mouse liver cancers, initiation of O-glycosylation by the GALNT glycosyl-transferases increases and shifts from the Golgi to the endoplasmic reticulum (ER). In a mouse liver cancer model, expressing an ER-targeted GALNT1 (ER-G1) massively increased tumor expansion, with median survival reduced from 23 to 10 weeks. In vitro cell growth was unaffected, but ER-G1 strongly enabled matrix degradation and tissue invasion. Unlike its Golgi-localized counterpart, ER-G1 glycosylates the matrix metalloproteinase MMP14, a process required for tumor expansion. Together, our results indicate that GALNTs strongly promote liver tumor growth after relocating to the ER.