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Sarcomas are a rare classification of tumor derived from tissues of mesenchymal origin including bone, fat, muscle, cartilage, and blood vessels. These tumors often grow rapidly and have limited treatment options with few significant therapeutic advances in recent years. Liposarcomas (LPSs), the most common type of malignant soft tissue sarcoma, are derived from mesenchymal progenitors that have undergone an adipogenic lineage commitment compared to their multipotent counterparts. Interestingly, the grade of differentiation within LPS can vary highly, and the differentiation status of these tumors can drastically affect prognosis and likelihood of metastasis, making tumor differentiation a potential mechanism to target in liposarcoma development. Here, we show that overexpression of the Hedgehog transcription factor Gli2 in dedifferentiated liposarcoma (DDLPS) cells represses adipogenic differentiation while simultaneously activating markers of osteoblast differentiation in vitro . In addition, we observed marked differences in cytokine expression and secretion, prompting us to perform orthotopic fat pad injections of control and Gli2 overexpressing DDLPS cells. Using flow cytometry, we observed distinct changes in fat pad macrophage populations, with a particular increase in M2-like macrophages. Taken together, we find that overexpression of Gli2 in DDLPS cells alters their differentiation capacity and interactions between tumor cells and macrophages, highlighting a novel role for this developmental transcription factor in liposarcoma pathogenesis.

The establishment and progression of bone metastatic breast cancer is supported by immunosuppressive myeloid populations that enable tumor growth by dampening the innate and adaptive immune response. Much work remains to understand how to target these tumor-myeloid interactions to improve treatment outcomes. Noncanonical Hedgehog signaling is an essential component of bone metastatic tumor progression, and prior literature suggests a potential role for Hedgehog signaling and its downstream effector Gli2 in modulating immune responses. In this work, we sought to identify if inhibition of noncanonical Hedgehog signaling alters the cytokine profile of osteolytic breast cancer cells and the subsequent communication between the tumor cells and myeloid cells. Examination of large patient databases revealed significant relationships between Gli2 expression and expression of markers of myeloid maturation and activation as well as cytokine expression. We found that treatment with HPI-1 reduced tumor cell expression of numerous cytokine genes, including CSF1 , CSF2 , and CSF3 , as well as CCL2 and IL6 . Secreted CSF-1 (M-CSF) was also reduced by treatment. Changes in tumor-secreted factors resulted in polarization of THP-1 monocytes toward a proinflammatory phenotype, characterized by increased CD14 and CD40 surface marker expression. We therefore propose M-CSF as a novel target of Hedgehog inhibition with potential future applications in altering the immune microenvironment in addition to its known roles in reducing tumor-induced bone disease., 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., (© 2024 The Authors.)

Due to the cellular plasticity that is inherent to cancer, the acquisition of resistance to therapy remains one of the biggest obstacles to patient care. In many patients, the surviving cancer cell subpopulation goes on to proliferate or metastasize, often as the result of dramatically altered cell signaling and transcriptional pathways. A notable example is the Hedgehog (Hh) signaling pathway, which is a driver of several cancer subtypes and aberrantly activated in a wide range of malignancies in response to therapy. This review will summarize the field's current understanding of the many roles played by Hh signaling in drug resistance and will include topics such as non-canonical activation of Gli proteins, amplification of genes which promote tolerance to chemotherapy, the use of hedgehog-targeted drugs and tool compounds, and remaining gaps in our knowledge of the transcriptional mechanisms at play., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Miller, Bennett and Rhoades.)

Liposarcomas are the most diagnosed soft tissue sarcoma, with most cases consisting of well-differentiated (WDLPS) or dedifferentiated (DDLPS) histological subtypes. While both tumor subtypes can have clinical recurrence due to incomplete resections, DDLPS often has worse prognosis due to a higher likelihood of metastasis compared to its well-differentiated counterpart. Unfortunately, targeted therapeutic interventions have lagged in sarcoma oncology, making the need for molecular targeted therapies a promising future area of research for this family of malignancies. In this work, previously published data were analyzed to identify differential pathways that may contribute to the dedifferentiation process in liposarcoma. Interestingly, Gli-mediated Hedgehog signaling appeared to be enriched in dedifferentiated adipose progenitor cells and DDLPS tumors, and coincidentally Gli1 is often co-amplified with MDM2 and CDK4, given its genomic proximity along chromosome 12q13-12q15. However, we find that Gli2, but not Gli1, is differentially expressed between WDLPS and DDLPS, with a noticeable co-expression signature between Gli2 and genes involved in ECM remodeling. Additionally, Gli2 co-expression had a noticeable transcriptional signature that could suggest Gli-mediated Hedgehog signaling as an associated pathway contributing to poor immune infiltration in these tumors.

When breast cancer metastasizes to bone, treatment options are limited. Failure to treat bone metastases is thought to be due to therapy-resistant features of the bone marrow microenvironment. Using a murine model of bone metastatic mammary carcinoma, we demonstrate that systemic delivery of polymer nanoparticles loaded with cyclic dinucleotide (CDN) agonists of stimulator of interferon genes (STING) inhibited tumor growth and bone destruction after 7 days of treatment. Each dose of STING-activating nanoparticles trafficked to the bone marrow compartment and was retained within the tumor microenvironment for over 24 hours, enhancing antitumor immunity through proinflammatory cytokine production and early T-cell activation. While acquired resistance mechanisms, including increased levels of immunosuppressive cytokines and the infiltration of regulatory T cells, ultimately limited antitumor efficacy after 2 weeks of treatment, bone protective effects remained. Overall, these studies demonstrate that STING pathway activation, here enabled using a nanomedicine approach to enhance CDN delivery to bone metastatic sites, can reprogram the immune contexture of the bone marrow to an antitumor phenotype that inhibits bone colonization of metastatic breast cancer cells and protects from tumor-mediated bone destruction., Significance: Bone metastases are difficult to treat due to the inaccessibility of the bone marrow compartment and the immunosuppressive microenvironment that protects resident stem cells. Packaging a STING agonist into a nanoparticle that enables systemic administration and drug accumulation at tumor sites overcomes both barriers to stymie metastatic breast cancer growth., Competing Interests: N.E. Bennett reports grants from NIH during the conduct of the study. A.R. Merkel reports grants from Verteran's Administration and non-financial support from Vanderbilt University Medical Center during the conduct of the study; grants from NIH Clinical and Translational Science Award and National Center for Advancing Translational Sciences outside the submitted work. M.A. Fischer reports grants from Incyte Corporation during the conduct of the study. M.R. Savona reports grants from ALX Oncology, Astex, Incyte, Takeda, TG Therapeutics; personal fees from BMS, CTI, Forma, Geron, Novartis, Sierra Oncology, Taiho; personal fees and other from Ryvu and Karyopharm outside the submitted work. J.A. Rhoades reports grants from Veterans Administration during the conduct of the study. S.A. Guelcher reports grants from Incyte Corporation during the conduct of the study. J.T. Wilson reports a patent to 10,696,985 issued and a patent to PCT/US2019/058945 pending. No disclosures were reported by the other authors., (© 2023 The Authors; Published by the American Association for Cancer Research.)