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Metastatic breast cancer is an intractable disease that responds poorly to immunotherapy. We show that p38MAPKα inhibition (p38i) limits tumor growth by reprogramming the metastatic tumor microenvironment in a CD4+ T cell-, IFNγ-, and macrophage-dependent manner. To identify targets that further increased p38i efficacy, we utilized a stromal labeling approach and single-cell RNA sequencing. Thus, we combined p38i and an OX40 agonist that synergistically reduced metastatic growth and increased overall survival. Intriguingly, patients with a p38i metastatic stromal signature had better overall survival that was further improved by the presence of an increased mutational load, leading us to ask if our approach would be effective in antigenic breast cancer. The combination of p38i, anti-OX40, and cytotoxic T-cell engagement cured mice of metastatic disease and produced long-term immunologic memory. Our findings demonstrate that a detailed understanding of the stromal compartment can be used to design effective antimetastatic therapies. Significance: Immunotherapy is rarely effective in breast cancer. We dissected the metastatic tumor stroma, which revealed a novel therapeutic approach that targets the stromal p38MAPK pathway and creates an opportunity to unleash an immunologic response. Our work underscores the importance of understanding the tumor stromal compartment in therapeutic design.

Metastatic breast cancer is an intractable disease that responds poorly to immunotherapy. We show that p38MAPKα inhibition (p38i) limits tumor growth by reprogramming the metastatic tumor microenvironment in a CD4+ T cell-, IFNγ-, and macrophage-dependent manner. To identify targets that further increased p38i efficacy, we utilized a stromal labeling approach and single-cell RNA sequencing. Thus, we combined p38i and an OX40 agonist that synergistically reduced metastatic growth and increased overall survival. Intriguingly, patients with a p38i metastatic stromal signature had better overall survival that was further improved by the presence of an increased mutational load, leading us to ask if our approach would be effective in antigenic breast cancer. The combination of p38i, anti-OX40, and cytotoxic T-cell engagement cured mice of metastatic disease and produced long-term immunologic memory. Our findings demonstrate that a detailed understanding of the stromal compartment can be used to design effective antimetastatic therapies.Significance:Immunotherapy is rarely effective in breast cancer. We dissected the metastatic tumor stroma, which revealed a novel therapeutic approach that targets the stromal p38MAPK pathway and creates an opportunity to unleash an immunologic response. Our work underscores the importance of understanding the tumor stromal compartment in therapeutic design.

Contains supplemental figures and legends

Table containing all of our reagents

Evaluation of cellular response to mTORC1 inhibition, BLI analysis of visceral metastases in PyMT-BO1 tumor-bearing mice receiving combination therapies, and αvβ3-NP-RAPA toxicity studies.

PDF file 401K, List of p38MAPK-dependent SASP factors and their overlap with publically available expression analyses from breast cancer-associated microenvironments

PDF file 62K, legends for supplemental figures

Breast cancer bone metastases are common and incurable. Tumoral integrin β3 (β3) expression is induced through interaction with the bone microenvironment. Although β3 is known to promote bone colonization, its functional role during therapy of established bone metastases is not known. We found increased numbers of β3+ tumor cells in murine bone metastases after docetaxel chemotherapy. β3+ tumor cells were present in 97% of post-neoadjuvant chemotherapy triple-negative breast cancer patient samples (n = 38). High tumoral β3 expression was associated with worse outcomes in both pre- and postchemotherapy triple-negative breast cancer groups. Genetic deletion of tumoral β3 had minimal effect in vitro, but significantly enhanced in vivo docetaxel activity, particularly in the bone. Rescue experiments confirmed that this effect required intact β3 signaling. Ultrastructural, transcriptomic, and functional analyses revealed an alternative metabolic response to chemotherapy in β3-expressing cells characterized by enhanced oxygen consumption, reactive oxygen species generation, and protein production. We identified mTORC1 as a candidate for therapeutic targeting of this β3-mediated, chemotherapy-induced metabolic response. mTORC1 inhibition in combination with docetaxel synergistically attenuated murine bone metastases. Furthermore, micelle nanoparticle delivery of mTORC1 inhibitor to cells expressing activated αvβ3 integrins enhanced docetaxel efficacy in bone metastases. Taken together, we show that β3 integrin induction by the bone microenvironment promotes resistance to chemotherapy through an altered metabolic response that can be defused by combination with αvβ3-targeted mTORC1 inhibitor nanotherapy. Our work demonstrates the importance of the metastatic microenvironment when designing treatments and presents new, bone-specific strategies for enhancing chemotherapeutic efficacy.

PDF file 229K, qRT-PCR validation of RNA-seq analysis and TNFalpha ELISA on p38i treated mice

PDF file 545K, SASP upregulation following bleomycin, NaB or replication-induced senescence. SASP mRNA stabilization in NaB-treated BJs and in bleomycin-treated IMR90s

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Additional details for methods and materials.

PDF file 194K, Senescence-associated beta-galactosidase staining of BJ fibroblasts and treatment of HaCaT-CBR cells with the p38MAPK small-molecule inhibitor SB203580

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Chemotherapy is important for cancer treatment, however, toxicities limit its use. While great strides have been made to ameliorate the acute toxicities induced by chemotherapy, long-term comorbidities including bone loss remain a significant problem. Chemotherapy-driven estrogen loss is postulated to drive bone loss, but significant data suggests the existence of an estrogen-independent mechanism of bone loss. Using clinically relevant mouse models, we showed that senescence and its senescence-associated secretory phenotype (SASP) contribute to chemotherapy-induced bone loss that can be rescued by depleting senescent cells. Chemotherapy-induced SASP could be limited by targeting the p38MAPK-MK2 pathway, which resulted in preservation of bone integrity in chemotherapy-treated mice. These results transform our understanding of chemotherapy-induced bone loss by identifying senescent cells as major drivers of bone loss and the p38MAPK–MK2 axis as a putative therapeutic target that can preserve bone and improve a cancer survivor's quality of life.Significance:Senescence drives chemotherapy-induced bone loss that is rescued by p38MAPK or MK2 inhibitors. These findings may lead to treatments for therapy-induced bone loss, significantly increasing quality of life for cancer survivors.

Gene set enrichment analyses showing effects of TNBC on tumor-promoting BMCs of young and old mice

Supplementary Data from Inhibition of the Stromal p38MAPK/MK2 Pathway Limits Breast Cancer Metastases and Chemotherapy-Induced Bone Loss

Controls and results from additional experiments to support primary data

PCR primer sequences

Detailed information for all antibodies

Supplemental Figures

Detailed information for controls and experiments to support primary data

Gene set enrichment analyses showing effects of age on tumor-promoting BMCs

Legends for supplemental figures 1-7

Supplementary Figure 1 from Senescent Stromal-Derived Osteopontin Promotes Preneoplastic Cell Growth

Alterations in the tissue microenvironment collaborate with cell autonomous genetic changes to contribute to neoplastic progression. The importance of the microenvironment in neoplastic progression is underscored by studies showing that fibroblasts isolated from a tumor stimulate the growth of preneoplastic and neoplastic cells in xenograft models. Similarly, senescent fibroblasts promote preneoplastic cell growth in vitro and in vivo. Because senescent cells accumulate with age, their presence is hypothesized to facilitate preneoplastic cell growth and tumor formation in older individuals. To identify senescent stromal factors directly responsible for stimulating preneoplastic cell growth, we carried out whole-genome transcriptional profiling and compared senescent fibroblasts with their younger counterparts. We identified osteopontin (OPN) as one of the most highly elevated transcripts in senescent fibroblasts. Importantly, reduction of OPN protein levels by RNA interference did not affect senescence induction in fibroblasts; however, it dramatically reduced the growth-promoting activities of senescent fibroblasts in vitro and in vivo, showing that OPN is necessary for paracrine stimulation of preneoplastic cell growth. In addition, we found that recombinant OPN was sufficient to stimulate preneoplastic cell growth. Finally, we show that OPN is expressed in senescent stroma within preneoplastic lesions that arise following 7,12-dimethylbenz(a)anthracene/12-O-tetradecanoylphorbol-13-acetate treatment of mice, suggesting that stromal-derived OPN-mediated signaling events affect neoplastic progression. [Cancer Res 2009;69(3):1230–9]

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Supplementary Figure 2 from Senescent Stromal-Derived Osteopontin Promotes Preneoplastic Cell Growth

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Supplementary Figure 3 from Senescent Stromal-Derived Osteopontin Promotes Preneoplastic Cell Growth

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Age is the largest risk factor for breast cancer development. While numerous changes arise with age, we posit that the accumulation of p16INKA4 (p16)+ senescent stromal cells—which express cytokines, chemokines, and enzymes together recognized as senescence-associated secretory phenotype (SASP)—promote cancer progression. Indeed, high p16 positivity in stroma strongly correlates with breast cancer recurrence. To investigate how senescent stroma impact tumorigenesis, we crossed MMTV-PyMT (PyMT) mice that spontaneously develop mammary tumors to INK-ATTAC (INK) mice, which allows selective elimination of p16+ cells. Depletion of p16+ stroma in PyMT/INK mice led to a significantly delayed tumor onset and changes in tumor-infiltrating immune cells, both of which could be recapitulated by treating PyMT mice with a senolytic drug. scRNA-seq analyses of murine and human tumor samples revealed that senescence is restricted to a specific cancer associated fibroblasts (CAF) subpopulation that expresses numerous immune and extracellular matrix SASP factors that could impact T cells and Natural Killer (NK) cells. We refer to these cells as senescent CAFs (senCAFs). To assess the impact of senCAFs on T and NK cells’ anti-tumor effect, we depleted each population and found that the elimination of senCAFs no longer restricted tumor development in the absence of NK cells. We thus focused on addressing how senCAFs modulate NK cell function. Together our data highlight how senescent CAFs contribute to mammary gland tumorigenesis by modifying tumor microenvironment. Citation Format: Jiayu (Jennifer) Ye, Ana Paula Delgado, Qihao Ren, Robert S. Powers, Sheila A. Stewart. Senescent cells promote breast cancer tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 85.

Cancer is a disease of the aged. While the accumulation of cell autonomous mutations contributes to tumorigenesis, the central role age-related changes in the tumor microenvironment play in the transformation process is becoming more fully appreciated. Underscoring the importance of an aged microenvironment in cancer development are findings that senescent fibroblasts, which accumulate with age, directly stimulate preneoplastic and neoplastic cell growth and tumor progression. Investigations into how senescent fibroblasts promote tumorigenesis revealed that they express a plethora of growth factors, extracellular matrix remodeling enzymes, chemokines, and cytokines collectively referred to as the senescence associated secretory phenotype (SASP). To identify a role for senescent stromal cells in a spontaneous model of breast cancer, we used single cell RNA-Sequencing (scRNA-Seq) to interrogate the cell types and their functional status in the MMTV-PyMT breast tumor model. This analysis revealed the presence of senescent cancer associated fibroblasts (senCAFs) that we also identified in a human triple negative breast cancer scRNA-Seq database. To establish a role for senCAFs in breast cancer, we mated the PyMT model to the INKATTAC (INK) mouse that allowed us to inducibly eliminate senescent cells. We found that the elimination of senCAFs reduced tumor growth and unleashed the killing power of NK cells. We will discuss the mechanism by which senCAFs impact NK cell killing. Citation Format: Sheila A. Stewart. Age-related changes in the tumor microenvironment drive tumor progression. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr SY17-03.

Breast cancer bone metastases are common and incurable. Tumoral integrin β3 (β3) expression is induced through interaction with the bone microenvironment. Although β3 is known to promote bone colonization, its functional role during therapy of established bone metastases is not known. We found increased numbers of β3+ tumor cells in murine bone metastases after docetaxel chemotherapy. β3+ tumor cells were present in 97% of post-neoadjuvant chemotherapy triple-negative breast cancer patient samples (n = 38). High tumoral β3 expression was associated with worse outcomes in both pre- and postchemotherapy triple-negative breast cancer groups. Genetic deletion of tumoral β3 had minimal effect in vitro, but significantly enhanced in vivo docetaxel activity, particularly in the bone. Rescue experiments confirmed that this effect required intact β3 signaling. Ultrastructural, transcriptomic, and functional analyses revealed an alternative metabolic response to chemotherapy in β3-expressing cells characterized by enhanced oxygen consumption, reactive oxygen species generation, and protein production. We identified mTORC1 as a candidate for therapeutic targeting of this β3-mediated, chemotherapy-induced metabolic response. mTORC1 inhibition in combination with docetaxel synergistically attenuated murine bone metastases. Furthermore, micelle nanoparticle delivery of mTORC1 inhibitor to cells expressing activated αvβ3 integrins enhanced docetaxel efficacy in bone metastases. Taken together, we show that β3 integrin induction by the bone microenvironment promotes resistance to chemotherapy through an altered metabolic response that can be defused by combination with αvβ3-targeted mTORC1 inhibitor nanotherapy. Our work demonstrates the importance of the metastatic microenvironment when designing treatments and presents new, bone-specific strategies for enhancing chemotherapeutic efficacy.

The impact of healthy aging on molecular programming of immune cells is poorly understood. Here, we report comprehensive characterization of healthy aging in human classical monocytes, with a focus on epigenomic, transcriptomic, and proteomic alterations, as well as the corresponding proteomic and metabolomic data for plasma, using healthy cohorts of 20 young and 20 older males (~27 and ~64 years old on average). For each individual, we performed eRRBS-based DNA methylation profiling, which allowed us to identify a set of age-associated differentially methylated regions (DMRs) – a novel, cell-type specific signature of aging in DNA methylome. Hypermethylation events were associated with H3K27me3 in the CpG islands near promoters of lowly-expressed genes, while hypomethylated DMRs were enriched in H3K4me1 marked regions and associated with age-related increase of expression of the corresponding genes, providing a link between DNA methylation and age-associated transcriptional changes in primary human cells.

Significant advances have been made towards understanding the role of immune cell-tumor interplay in either suppressing or promoting tumor growth, progression, and recurrence, however, the roles of additional stromal elements, cell types and/or cell states remain ill-defined. The overarching goal of this NCI-sponsored workshop was to highlight and integrate the critical functions of non-immune stromal components in regulating tumor heterogeneity and its impact on tumor initiation, progression, and resistance to therapy. The workshop explored the opposing roles of tumor supportive versus suppressive stroma and how cellular composition and function may be altered during disease progression. It also highlighted microenvironment-centered mechanisms dictating indolence or aggressiveness of early lesions and how spatial geography impacts stromal attributes and function. The prognostic and therapeutic implications as well as potential vulnerabilities within the heterogeneous tumor microenvironment were also discussed. These broad topics were included in this workshop as an effort to identify current challenges and knowledge gaps in the field.

The purpose of this article is to describe programs and strategies dissuasive of Aboriginal youth gang involvement. Individual approaches target areas such as antisocial behavior, personal challenges, and negative thinking patterns. Family-orientated approaches reaffirm family values as a means to deter youth from gang association. Providing positive opportunities for youth to interact with community role models and to partake in community programs are also dissuasive to the proliferation of Aboriginal youth gangs. Although information herein is intended to tackle Aboriginal youth gang issues, it can also be useful in addressing peripheral social issues within communities, in general.

Chemotherapy is important for cancer treatment, however, toxicities limit its use. While great strides have been made to ameliorate the acute toxicities induced by chemotherapy, long-term comorbidities including bone loss remain a significant problem. Chemotherapy-driven estrogen loss is postulated to drive bone loss, but significant data suggests the existence of an estrogen-independent mechanism of bone loss. Using clinically relevant mouse models, we showed that senescence and its senescence-associated secretory phenotype (SASP) contribute to chemotherapy-induced bone loss that can be rescued by depleting senescent cells. Chemotherapy-induced SASP could be limited by targeting the p38MAPK-MK2 pathway, which resulted in preservation of bone integrity in chemotherapy-treated mice. These results transform our understanding of chemotherapy-induced bone loss by identifying senescent cells as major drivers of bone loss and the p38MAPK–MK2 axis as a putative therapeutic target that can preserve bone and improve a cancer survivor's quality of life. Significance: Senescence drives chemotherapy-induced bone loss that is rescued by p38MAPK or MK2 inhibitors. These findings may lead to treatments for therapy-induced bone loss, significantly increasing quality of life for cancer survivors.