ABS 024: Utilizing a Syngeneic Murine Model of Dedifferentiated Liposarcoma to Explore Mechanisms of Response and Resistance to Standard-of-Care Systemic Therapies

Grace Y. Lee ¹, Lexi-Ann F. Golden ², Emma Kenna ² ⁴, Brynn Kaczkofsky ³, Yazan Ahlmadi ³, Amanda Shafer ³, Jodi Wilkowski ³, & Christina V. Angeles ² ³​

¹ College of Literature, Science, and the Arts; University of Michigan, Ann Arbor, MI
² Cancer Biology; University of Michigan Medical School, Ann Arbor, MI
³ Department of Surgery; University of Michigan Medicine, Ann Arbor, MI
⁴ Department of Computational Medicine and Bioinformatics; University of Michigan Medicine, Ann Arbor, MI​

The Van Wickle Journal (2026) Volume 2, ABS024

Introduction: Soft tissue sarcomas (STS) are rare with an annual incidence of approximately 2-5 per 100,000 per year with roughly 5,000 deaths per year. Dedifferentiated liposarcoma (DDLPS) is one of the main subtypes that presents significant clinical challenges. Doxorubicin is the standard systemic chemotherapy, yet fewer than 30% of patients respond effectively. Additionally, while patient-derived xenografts (PDXs) have shown efficacious response to targeted therapies, these drugs have failed in patient clinical trials. This study examines chemotherapeutic sensitivity and transcriptional response in murine and human DDLPS models and assesses in vivo efficacy in an immune-competent mouse model in hopes to better inform patient treatment strategies.

Doxorubicin was consistently effective in both murine and human DDLPS lines (IC₅₀ ~230–460 nM), with healthy 3T3 controls exhibiting less sensitivity. N1018 showed slightly higher resistance (IC₅₀ 460 nM) compared to N1011 and N1343 (IC₅₀ 230 nM). Selinexor demonstrated selective activity in N1011 (IC₅₀ = 400 nM), while trabectedin showed moderate efficacy (IC₅₀ = 500–750 nM), and dacarbazine was effective only in N1011. In vivo, higher doses of doxorubicin significantly slowed tumor growth compared to the low dose and vehicle control. Tumors taken at endpoint from in vivo experimentation showed an increasing trend of exhaustion markers PD1+, LAG3+, and TOX+ as doxorubicin dosage increased from flow cytometry analysis.

Murine and human DDLPS cell lines show consistent doxorubicin sensitivity. Specifically N1011 cells were also uniquely sensitive to selinexor, with minimal sensitivity to other later-line treatments, mimicking the lack of therapeutic efficacy seen in human DDLPS. The in vivo validation using a syngeneic murine model highlights its relevance for further mechanistic studies and the development of rational drug combination strategies in DDLPS.

Methods: In vitro murine DDLPS cell lines (N1011, N1018, N1343) or human DDLPS cell lines (LPS141, DDLS8817) were grown in 10cm plates and then plated and drug treated in 96-well plates. Dose response curves were analyzed via CYQUANT Cell Proliferation Assays. In vivo, N1018 was implanted into the subcutaneous (s.c.) flank fat pad of wild-type (WT) C57BL6/J mice. Once tumors reached 0.3 – 0.5 cm2, mice were randomized to doxorubicin (2.5 or 5 mg/kg) or control (PBS). Treatments were administered via intraperitoneal injection (i.p.) 2x weekly until the tumor hits 2.0 cm in diameter or other humane endpoints. Tumors were measured 3x per week with digital calipers. Flow cytometry analysis was performed on tumors taken at the endpoint of control and treatment groups.

Results: We show that the ACPP-derived cell lines are an accurate model of DDLPS for pre-clinical therapeutic testing showcasing similar sensitivity to first-line doxorubicin treatment as patient-derived cell lines.​ The cell lines also show general resistance to second-line DDLPS therapies, with N1011 demonstrating unique sensitivity to Selinexor.​ We have also shown expected responses in vivo where N1018 shows a modest, yet non-durable growth delay to 2.5 or 5 mg/kg doxorubicin in vivo.​ N1018 also exhibits an upward trend of exhaustion marker expression in a dose-dependent manner with doxorubicin treatment in-vivo.

Discussion: Future directions include using RNAseq and ATACseq to explore broader transcriptional and epigenetic changes to treated ACPP-derived cell lines compared to patient-derived cell lines, confirm hits with RT-qPCR and western blots, & test hypotheses of mechanisms of response and resistance using ACPP-cell lines in vivo. Additionally, given the increased expression of exhaustion markers with doxorubicin, in vivo combinations of doxorubicin and anti-PD1 or anti-LAG3 inhibitors are also underway. ​