Summary Increased collagen deposition by breast cancer (BC)-associated mesenchymal stem/multipotent stromal cells (MSC) promotes metastasis, but the mechanisms are unknown. Here, we report that the collagen receptor Discoidin Domain Receptor 2 (DDR2) is essential for stromal-BC communication. In human BC metastasis DDR2 is concordantly upregulated in metastatic cancer and multipotent mesenchymal stromal cells. In MSCs isolated from human BC metastasis DDR2 maintains a fibroblastic phenotype with collagen deposition and induces pathological activation of DDR2 signaling in BC cells. Loss of DDR2 in MSCs impairs their ability to promote DDR2 phosphorylation in BC cells, BC cell alignment, migration, and metastasis. Female ddr2-deficient mice homozygous for the slie mutation show inefficient spontaneous BC metastasis. These results document a role for mesenchymal stem cell DDR2 in metastasis, and suggest a therapeutic approach for metastatic BC.

Increasing evidence supports that the epithelial to mesenchymal transition (EMT) in breast cancer cells generates tumor initiating cells (TICs) but the contribution of the tumor microenvironment to these programs needs further elucidation. CCN6 (WISP3) is a secreted matrix-associated protein (36.9 kDa) of the CCN family (named after CTGF, Cyr61 and Nov) that is reduced or lost in invasive carcinomas of the breast with lymph node metastasis and in inflammatory breast cancer. CCN6 exerts breast cancer growth and invasion inhibitory functions, but the mechanisms remain to be defined. In the present study we discovered that ectopic CCN6 overexpression in triple negative (TN) breast cancer cells and in cells derived from patients is sufficient to induce a mesenchymal to epithelial transition (MET) and to reduce TICs. In vivo, CCN6 overexpression in the TIC population of MDA-MB-231 cells delayed tumor initiation, reduced tumor volume, and inhibited the development of metastasis. Our studies reveal a novel CCN6/Slug signaling axis that regulates Notch1 signaling activation, epithelial cell phenotype and breast TICs, which requires the conserved thrombospondin type 1 (TSP1) motif of CCN6. The relevance of these data to human breast cancer is highlighted by the finding that CCN6 protein levels are inversely correlated with Notch1 intracellular activated form (NICD1) in 69.5% of invasive breast carcinomas. These results demonstrate that CCN6 regulates epithelial and mesenchymal states transition and TIC programs, and pinpoint one responsible mechanism.

Background: Accumulating evidence suggests that mesenchymal stem cells (MSCs) are recruited to the tumor microenvironment and play roles in tumor progression; however the underlying mechanisms by which MSCs promote breast cancer migration and invasion need further investigation. Studies have demonstrated that collagen plays an important role in breast tumorigenesis by activating signaling pathways. We hypothesize that MSCs may promote breast cancer progression through regulating collagen-induced signaling in breast cancer cells. Methods: We isolated carcinoma-associated MSCs (CA-MSCs) from human breast cancer metastasis to lymph node (LNM) and liver (LM). CA-MSCs were subjected to multilineage differentiation assays and labeled with Ds-Red. COAL I expression and its receptor discoidin domain receptor 2 (DDR2) were downregulated in the CA-MSCs-DsRED using specific shRNA. We established single culture and co-cultures of CA-MSCs with GFP labeled breast cancer cells (BCCs) MDA-MB-231 and MCF10ACA1a which were used for Live Imaging Microscopy, IHC, RT-PCR, WB, immunofluorescence, 3D proliferation and invasion assays, and in vivo xenograft experiments. Results: CA-MSCs had spindle morphology, normal karyotype, were nontumorigenic in vivo, and possessed tri-lineage differentiation ability (osteoblast, adipocyte, and chondrocyte). CA-MSCs exhibited high mRNA and protein levels of collagen I (COAL I) and its receptor DDR2. ShRNA-mediated knockdown of COAL I or DDR2 in CA-MSCs induced a change in morphology towards epithelial, decreased expression of epithelial to mesenchymal transition (EMT) markers, and impaired migration. Co-culture of CA-MSCs with BCCs led to increased BCC proliferation, EMT, invasion, and increased DDR2 expression in BCCs compared to single cultures of BCCs, which was blocked by COAL1 and DDR2 shRNA in CA-MSCs. Live imaging studies revealed that shCOAL1 and shDDR2 was sufficient to completely disrupt the organized migration pattern of BCCs aligned with CA-MSCs. In vivo, xenografts derived from MDA-MB-231 cells co-cultured with shControl CA-MSCs exhibited increased collagen I deposition in the tumor microenvironment, increased tumor growth, and metastasis compared to the single cultures of MDA-MB-231 cells. Remarkably, shDDR2 in CA-MSCs reduced tumorigenesis and metastasis. Conclusion: We successfully isolated and characterized CA-MSCs, confirming their presence in human breast cancer metastasis. Our findings suggest that collagen I and its receptor DDR2 play a role in directional migration of breast cancer cells in alignment with CA-MSCs, a function that may be implicated in breast cancer invasion and metastasis. Downregulation of collagen I expression and signaling reduces tumor growth and metastasis in vivo. Modifying tumor microenvironment by manipulating collagen I and/or DDR2 levels in MSCs might be therapeutically useful in preventing metastasis. Citation Format: Maria E. Gonzalez, Emily Martin, Caroline Arellano-Gracia, Arjun Lama, Celina G. Kleer. Mesenchymal stem cell-derived collagen I plays a role in organizing breast cancer cell migration and metastasis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4397.

Older adults hospitalized with severe COVID-19 are at higher risk of experiencing serious in-hospital outcomes and long-term health consequences following discharge. Declines in health and functional ability post-hospitalization are important infection-related outcomes. This study’s aim was to examine functional recovery one year following COVID-19 hospitalization. Twenty-one adults ≥60 years of age hospitalized with confirmed COVID-19 infection between 3/2020–5/2020 in Southeast Michigan completed a survey 9–15 months post-discharge including items from the Fried Frailty score, Short Form 36 Physical Assessment, PROMIS Dyspnea Scale, and the World Health Organization Disability Assessment Schedule. Mean age at hospital admission was 69 (standard deviation 7). Half of participants (52%) indicated they had too little energy to do the things they wanted to do, 52% (n=11) indicated moderate to severe shortness of breath when walking up two flights of stairs, and 43% (n=9) indicated they were limited a lot in walking several blocks. Additionally, 57% (n=12) indicated they were severely or extremely emotionally affected by their health due to their COVID-19 infection. Results were similar in only those ≥70 years (n=7). Our survey indicates that half of patients hospitalized with severe COVID-19 from the first infection wave in Southeast Michigan are significantly affected up to a year or more after their initial infection, and may benefit from long-term outpatient care. More research is needed to inform development of effective treatments for the long-term emotional and physical impacts of severe COVID-19.