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Idiopathic pulmonary fibrosis (IPF) is an age-related disease with poor prognosis and limited therapeutic options. Activation of lung fibroblasts and differentiation to myofibroblasts are the principal effectors of disease pathology, but damage and senescence of alveolar epithelial cells, specifically type II (ATII) cells, has recently been identified as a potential trigger event for the progressive disease cycle. Targeting ATII senescence and the senescence-associated secretory phenotype (SASP) is an attractive therapeutic strategy; however, translatable primary human cell models that enable mechanistic studies and drug development are lacking. Here, we describe a novel system of conditioned medium (CM) transfer from bleomycin-induced senescent primary alveolar epithelial cells (AEC) onto normal human lung fibroblasts (NHLF) that demonstrates an enhanced fibrotic transcriptional and secretory phenotype compared to non-senescent AEC CM treatment or direct bleomycin damage of the NHLFs. In this system, the bleomycin-treated AECs exhibit classical hallmarks of cellular senescence, including SASP and a gene expression profile that resembles aberrant epithelial cells of the IPF lung. Fibroblast activation by CM transfer is attenuated by pre-treatment of senescent AECs with the senolytic Navitoclax and AD80, but not with the standard of care agent Nintedanib or senomorphic JAK-targeting drugs (e.g., ABT-317, ruxolitinib). This model provides a relevant human system for profiling novel senescence-targeting therapeutics for IPF drug development.

Breast cancer has a high predilection for spreading to bone with approximately 70% of patients who succumb to disease harboring bone disseminated tumor cells. Despite this high prevalence, treatments for bone metastatic breast cancer predominantly manage morbidities, including pain and hypercalcemia, rather than reducing bone metastasis incidence or growth. Histone deacetylase inhibitors (HDACi), including panobinostat, entinostat, and valproic acid, typically slow primary tumor progression and are currently in clinical trials for the treatment of many cancers, including primary and metastatic breast cancer, but their effects on bone metastatic disease have not been examined in preclinical models. We report that treatment with the HDACi panobinostat, but not entinostat or valproic acid, significantly reduced trabecular bone volume in tumor-naïve mice, consistent with previous reports of HDACi-induced bone loss. Surprisingly, treatment with entinostat or panobinostat, but not valproic acid, increased tumor burden and incidence in an experimental model of breast cancer bone metastasis. In vitro, multiple HDACi stimulated expression of pro-osteolytic genes in breast tumor cells, suggesting this may be a mechanism by which HDACi fuel tumor growth. In support of this, combination therapy of panobinostat or entinostat with the antiresorptive bisphosphonate zoledronic acid prevented bone metastatic progression; however, the addition of zoledronic acid to panobinostat therapy failed to fully correct panobinostat-induced bone loss. Together these data demonstrate that select HDACi fuel bone metastatic growth and provide potential mechanistic and therapeutic avenues to offset these effects. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research., (© 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.)

Breast cancer cells frequently disseminate to the bone marrow, where they either induce osteolysis or enter a dormant state. Downregulation of leukemia inhibitory factor receptor (LIFR), a known breast tumor suppressor, enables otherwise dormant MCF7 human breast cancer cells to become aggressively osteolytic. Hypoxia (low oxygen tensions), which may develop in tumors as a pathological response to the metabolic demands of the proliferating cells and as a physiological state in the bone, downregulates LIFR in breast cancer cells independent of hypoxia-inducible factor (HIF) signaling. However, the mechanism by which LIFR is repressed in hypoxia is unknown. Histone deacetylase (HDAC) inhibitors stimulate LIFR by increasing histone acetylation in the proximal promoter and induce a dormancy phenotype in breast cancer cells inoculated into the mammary fat pad. We therefore aimed to determine whether hypoxia alters histone acetylation in the LIFR promoter, and whether HDAC inhibitors effectively stimulate LIFR in breast cancer cells residing in hypoxic microenvironments. Herein, we confirmed that disseminated MCF7 cells became hypoxic in the bone and that hypoxia increased the epigenetic transcriptional repressor H3K9me3 in the distal LIFR promoter while H3K9ac, which promotes transcription, was significantly reduced. Furthermore, HDAC inhibitor treatment rescued hypoxic repression and dramatically increased expression of LIFR, p38β, and p21, which regulate tumor dormancy. In a second model of LIFR repression, in which parathyroid hormone-related protein (PTHrP) suppresses LIFR expression, we found that PTHrP binds to the distal LIFR promoter, and that PTHrP suppression of LIFR protein is similarly reversed by HDAC inhibitor treatment. Together, these data suggest that HDAC inhibitors stimulate LIFR regardless of the way it is repressed by the microenvironment., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 Published by Elsevier GmbH.)

Hypoxia is a common feature in tumors and induces signaling that promotes tumor cell survival, invasion, and metastasis, but the impact of hypoxia inducible factor (HIF) signaling in the primary tumor on dissemination to bone in particular remains unclear. To better understand the contributions of hypoxia inducible factor 1 alpha (HIF1α), HIF2α, and general HIF pathway activation in metastasis, we employ a PyMT-driven spontaneous murine mammary carcinoma model with mammary specific deletion of Hif1α, Hif2α, or von Hippel-Lindau factor (Vhl) using the Cre-lox system. Here we show that Hif1α or Hif2α deletion in the primary tumor decreases metastatic tumor burden in the bone marrow, while Vhl deletion increases bone tumor burden, as hypothesized. Unexpectedly, Hif1α deletion increases metastatic tumor burden in the lung, while deletion of Hif2α or Vhl does not affect pulmonary metastasis. Mice with Hif1α deleted tumors also exhibit reduced bone volume as measured by micro computed tomography, suggesting that disruption of the osteogenic niche may be involved in the preference for lung dissemination observed in this group. Thus, we reveal that HIF signaling in breast tumors controls tumor dissemination in a site-specific manner., (© 2021. The Author(s).)

Despite advances in breast cancer treatment, residual disease driven by dormant tumor cells continues to be a significant clinical problem. Leukemia inhibitory factor receptor (LIFR) promotes a dormancy phenotype in breast cancer cells and LIFR loss is correlated with poor patient survival. Herein, we demonstrate that histone deacetylase inhibitors (HDACi), which are in phase III clinical trials for breast cancer, epigenetically induced LIFR and activated a pro-dormancy program in breast cancer cells. HDACi slowed breast cancer cell proliferation and reduced primary tumor growth. Primary breast tumors from HDACi-treated patients had increased LIFR levels and reduced proliferation rates compared to pre-treatment levels. Recent Phase II clinical trial data studying entinostat and azacitidine in metastatic breast cancer revealed that induction of several pro-dormancy genes post-treatment was associated with prolonged patient survival. Together, these findings suggest HDACi as a potential therapeutic avenue to promote dormancy, prevent recurrence, and improve patient outcomes in breast cancer., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Metastasis is the leading cause of cancer-related deaths, and greater knowledge of the metastatic microenvironment is necessary to effectively target this process. Microenvironmental changes occur at distant sites prior to clinically detectable metastatic disease; however, the key niche regulatory signals during metastatic progression remain poorly characterized. Here, we identify a core immune suppression gene signature in pre-metastatic niche formation that is expressed predominantly by myeloid cells. We target this immune suppression program by utilizing genetically engineered myeloid cells (GEMys) to deliver IL-12 to modulate the metastatic microenvironment. Our data demonstrate that IL12-GEMy treatment reverses immune suppression in the pre-metastatic niche by activating antigen presentation and T cell activation, resulting in reduced metastatic and primary tumor burden and improved survival of tumor-bearing mice. We demonstrate that IL12-GEMys can functionally modulate the core program of immune suppression in the pre-metastatic niche to successfully rebalance the dysregulated metastatic microenvironment in cancer., Competing Interests: Declaration of interests S.K., D.W.B., H.Q., and R.N.K. are inventors on international patent application no. PCT/US2020/17515, “Genetically modified hematopoietic stem and progenitor cells (HSPCs) and mesenchymal cells as a platform to reduce or prevent metastasis, treat autoimmune and inflammatory disorders, and rebalance the immune milieu and dysregulated niches.” The remaining authors have no competing interests. Inclusion and diversity One or more of the authors of this paper self-identifies as an underrepresented ethnic minority in science. One or more of the authors of this paper received support from a program designed to increase minority representation in science. One or more of the authors of this paper self-identifies as living with a disability. One or more of the authors of this paper self-identifies as a member of the LGBTQ+ community., (Published by Elsevier Inc.)

A significant proportion of breast cancer patients develop bone metastases, but the mechanisms regulating tumor cell dissemination from the primary site to the skeleton remain largely unknown. Using a novel model of spontaneous bone metastasis derived from human ER+ MCF7 cells, molecular profiling revealed increased PREX1 expression in a cell line established from bone-disseminated MCF7 cells (MCF7b), which were more migratory, invasive, and adhesive in vitro compared with parental MCF7 cells, and this phenotype was mediated by PREX1. MCF7b cells grew poorly in the primary tumor site when reinoculated in vivo, suggesting that these cells are primed to grow in the bone, and were enriched in skeletal sites of metastasis over soft tissue sites. Skeletal dissemination from the primary tumor was reversed with PREX1 knockdown, indicating that PREX1 is a key driver of spontaneous dissemination of tumor cells from the primary site to the bone marrow. In breast cancer patients, PREX1 levels are significantly increased in ER+ tumors and associated with invasive disease and distant metastasis. Together, these findings implicate PREX1 in spontaneous bone dissemination and provide a significant advance to the molecular mechanisms by which breast cancer cells disseminate from the primary tumor site to bone.

Purpose of Review: The goal of this review is to summarize recent experimental and clinical evidence for metastatic latency and the molecular mechanisms that regulate tumor dormancy in the bone., Recent Findings: Tumor dormancy contributes to the progression of metastasis and thus has significant clinical implications for prognosis and treatment. Tumor-intrinsic signaling and specialized bone marrow niches play a pivotal role in determining the dormancy status of bone disseminated tumor cells. Experimental models have provided significant insight into the effects of the bone microenvironment on tumor cells; however, these models remain limited in their ability to study dormancy. Despite recent advances in the mechanistic understanding of how tumor cells remain dormant in the bone for prolonged periods of time, the signals that trigger spontaneous dormancy escape remain unclear. This review highlights the need for further investigation of mechanisms underlying tumor dormancy using clinically relevant models.

Recent findings indicate that elderly patients with acute kidney injury (AKI) have an increased incidence of progression to chronic kidney disease (CKD) due to incomplete recovery from an acute insult. In the current study, a co-morbid model of AKI was developed to better mimic the patient population and to investigate whether age exacerbates the fibrosis and inflammation that develop in the sequelae of progressive kidney disease following acute injury. Young (8-10 weeks) and aged (46-49 weeks) C57BL/6 mice were subjected to 30 min bilateral renal ischemia-reperfusion (I/R) to induce AKI. The aged animals have greater mortality and prolonged elevation of plasma creatinine correlating with less tubular epithelial cell proliferation compared to the young. Six weeks post-reperfusion, interstitial fibrosis is greater in aged kidneys based on picrosirius red staining and immunolocalization of cellular fibronectin, collagen III and collagen IV. Aged kidneys 6 weeks post-reperfusion also express higher levels of p53 and p21 compared to the young, correlating with greater increases in senescence associated (SA) β-galactosidase, a known marker of cellular senescence. A higher influx of F4/80(+) macrophages and CD4(+) T lymphocytes is measured and is accompanied by increases in mRNA of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α). Importantly, microvascular density is significantly less, correlating with an increase in nitro-tyrosine, a marker of oxidative stress. Collectively, these data demonstrate that prolonged acute injury in the aged animals results in an accelerated progression of kidney disease in a chronic state.

Pasteurella aerogenes was isolated from the uterus and peritoneal cavity of a rabbit which died 4 days after abortion. Histopathologic observations confirmed a bacterial infection. Mouse pathogenicity tests indicated that this organism was an opportunistic pathogen that might have been responsible for the stillbirths. The cultural and biochemical characteristics of this isolate were similar to those of the Pasteurella aerogenes isolated from swine. This is the first report describing the isolation of Pasteurella aerogenes from a rabbit.