Steven H. Sun

Introduction: Soft tissue sarcomas are a diverse group of rare cancers, with approximately 15%–20% found in the retroperitoneum. Liposarcomas (LPS) make up approximately half of all retroperitoneal (RP) sarcomas, with most cases classified as either well‐differentiated (WD) or dedifferentiated (DD). DD LPS is more aggressive, with a higher local recurrence rate and risk of distant metastasis compared to WD LPS. The purpose of this review is to outline surgical management of RP LPS and highlight the multimodal treatment strategies for both primary and recurrent disease, along with considerations for their effective implementation. Methods: The current medical literature was reviewed for studies focused on retroperitoneal liposarcoma and its treatment with surgery, radiation, and chemotherapy. The data was interpreted and compiled in the context of expert clinical experience. Results: Along with histopathologic analysis, tumor biology can inform patient prognosis. Surgery, the standard treatment for RP LPS, can be either curative or palliative. In primary disease, an attempt should be made to achieve wide surgical margins when feasible. Surgery for recurrent disease requires careful timing and an understanding of the potential benefit versus risk. Neoadjuvant radiation therapy can improve local control of RP LPS; however, data supporting the use of neoadjuvant chemotherapy are currently lacking. Conclusion: Multimodality treatment of RP LPS is complex and requires consideration of tumor biology and extent of disease, along with individual patient characteristics. Multidisciplinary team collaboration is critical for improving outcomes in patients with RP LPS.

Background: Pleomorphic liposarcoma (PLPS) is an ultra‐rare malignancy distinct from well‐differentiated/dedifferentiated and myxoid liposarcoma. In this study, we sought to (1) assess outcomes after surgery for primary, non‐metastatic PLPS and (2) explore potential indications for multimodality therapy.Methods: Clinicopathologic data were retrospectively collected for patients treated from 2002 to 2019 at our sarcoma referral center. Descriptive data were summarized and Kaplan–Meier plots were constructed for overall survival (OS) and crude cumulative incidences (CCI) of disease‐specific death (DSD), local recurrence (LR), and distant metastasis (DM). Univariable models were performed to assess the association of specific variables of interest on outcome.Results: Forty‐four pathology‐verified PLPS cases were included in this study. Median tumor size was 8.5 cm; 75% were FNCLCC Grade 3. All patients underwent complete resection, including 15 patients (34%) who required re‐excision to secure microscopic negative margins. Radiation therapy was given to 75% of patients, chemotherapy in 36%. At 5 years, OS was 75.3%; CCI of DSD, LR, and DM were 17.5%, 2.3%, and 32.5%. Larger tumor size was strongly associated with worse OS (p = 0.028) and DSD (p ≤ 0.001). A subgroup of patients (n = 10, 23%) with smaller, predominantly Grade 2 tumors underwent surgery alone without any LR or DM event at a median follow‐up of 7.9 years.Conclusions: In PLPS, aggressive surgery and when appropriate, radiation therapy, results in excellent local control. Chemotherapy can be considered for larger tumors. Patients with smaller, Grade 2 tumors may be potentially cured with surgery alone.

Fluorescent nanodiamonds (FNDs) are carbon-based nanomaterials that emit bright, photostable fluorescence and exhibit a modifiable surface chemistry. Myeloid-derived suppressor cells (MDSCs) are an immunosuppressive cell population known to expand in cancer patients and contribute to worse patient outcomes. To target MDSC, glycidol-coated FND were conjugated with antibodies against the murine MDSC markers, CD11b and GR1 (dual-Ab FND). In vitro, dual-Ab FND uptake by murine MDSC was significantly higher than IgG-coated FND (94.7% vs. 69.0%, p < 0.05). In vivo, intra-tumorally injected dual-Ab FND primarily localized to the tumor 2 and 24 h post-injection, as measured by in vivo fluorescence imaging and flow cytometry analysis of the spleen and tumor. Dual-Ab FND were preferentially taken up by intra-tumoral MDSC, representing 87.1% and 83.0% of FND+ cells in the tumor 2 and 24 h post-injection, respectively. Treatment of mice with anti-PD-L1 immunotherapy prior to intra-tumoral injection of dual-Ab FND did not significantly alter the uptake of FND by MDSC. These results demonstrate the ability of our novel dual-antibody conjugated FND to target MDSC and reveal a potential strategy for targeted delivery to other specific immune cell populations in future cancer research.

Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells that expand dramatically in many cancer patients. This expansion contributes to immunosuppression in cancer and reduces the efficacy of immune-based cancer therapies. One mechanism of immunosuppression mediated by MDSCs involves production of the reactive nitrogen species peroxynitrite (PNT), where this strong oxidant inactivates immune effector cells through destructive nitration of tyrosine residues in immune signal transduction pathways. As an alternative to analysis of nitrotyrosines indirectly generated by PNT, we used an endoplasmic reticulum (ER)-targeted fluorescent sensor termed PS3 that allows direct detection of PNT produced by MDSCs. When the MDSC-like cell line MSC2 and primary MDSCs from mice and humans were treated with PS3 and antibody-opsonized TentaGel microspheres, phagocytosis of these beads led to production of PNT and generation of a highly fluorescent product. Using this method, we show that splenocytes from a EMT6 mouse model of cancer, but not normal control mice, produce high levels of PNT due to elevated numbers of granulocytic (PMN) MDSCs. Similarly, peripheral blood mononuclear cells (PBMCs) isolated from blood of human melanoma patients produced substantially higher levels of PNT than healthy human volunteers, coincident with higher peripheral MDSC levels. The kinase inhibitor dasatinib was found to potently block the production of PNT both by inhibiting phagocytosis in vitro and by reducing the number of granulocytic MDSCs in mice in vivo, providing a chemical tool to modulate the production of this reactive nitrogen species (RNS) in the tumor microenvironment.

Background: fluorescent nanodiamonds (FND) are nontoxic, infinitely photostable nanoparticles that emit near-infrared fluorescence and have a modifiable surface allowing for the generation of protein–FND conjugates. FND-mediated immune cell targeting may serve as a strategy to visualize immune cells and promote immune cell activation. Methods: uncoated-FND (uFND) were fabricated, coated with glycidol (gFND), and conjugated with immunoglobulin G (IgG–gFND). In vitro studies were performed using a breast cancer/natural killer/monocyte co-culture system, and in vivo studies were performed using a breast cancer mouse model. Results: in vitro studies demonstrated the targeted immune cell uptake of IgG–gFND, resulting in significant immune cell activation and no compromise in immune cell viability. IgG–gFND remained at the tumor site following intratumoral injection compared to uFND which migrated to the liver and kidneys. Conclusion: antibody-conjugated FND may serve as immune drug delivery vehicles with “track and trace capabilities” to promote directed antitumor activity and minimize systemic toxicities.

We present a biosensing platform that uses spatial electroluminescent (EL) illumination combined with charge-coupled device (CCD)-based detection for fluorescence measurements. The resulting EL-CCD detector platform was used to monitor different protease activities with substrates labeled for fluorescence resonance energy transfer (FRET)-based assays. The first uses a commercial FITC/DABCYL-SNAP-25 peptide substrate to monitor the activity of the light chain derivative (LcA) of botulinum neurotoxin A, achieving a limit of detection (LOD) of 1.25 nM (62 ng/ml). The second protease activity assay measured trypsin proteolysis using peptide substrates immobilized onto semiconductor quantum dot (QD) nanoparticles with a LOD of 6.2 nM trypsin (140 ng/ml). The specific ovomucoid inhibition of trypsin activity was also monitored. The highlighted studies clearly demonstrate the utility of the EL-CCD detector platform for monitoring fluorescent-based protease activity assays with potential healthcare applications, including point-of-care diagnostics.