SAR405838: A Novel and Potent Inhibitor of the MDM2:p53 Axis for the Treatment of Dedifferentiated Liposarcoma

Comparison of three-dimensional cell culture techniques of dedifferentiated liposarcoma and their integration with future research

Background: Dedifferentiated liposarcoma is a formidable sarcoma subtype due to its high local recurrence rate and resistance to medical treatment. While 2D cell cultures are still commonly used, 3D cell culture systems have emerged as a promising alternative, particularly scaffold-based techniques that enable the creation of 3D models with more accurate cell-stroma interactions. Objective: To investigate how 3D structures with or without the scaffold existence would affect liposarcoma cell lines growth morphologically and biologically. Methods: Lipo246 and Lipo863 cell lines were cultured in 3D using four different methods; Matrigel® ECM scaffold method, Collagen ECM scaffold method, ULA plate method and Hanging drop method, in addition to conventional 2D cell culture methods. All samples were processed for histopathological analysis (HE, IHC and DNAscope™), Western blot, and qPCR; moreover, 3D collagen-based models were treated with different doses of SAR405838, a well-known inhibitor of MDM2, and cell viability was assessed in comparison to 2D model drug response. Results: Regarding morphology, cell lines behaved differently comparing the scaffold-based and scaffold-free methods. Lipo863 formed spheroids in Matrigel® but not in collagen, while Lipo246 did not form spheroids in either collagen or Matrigel®. On the other hand, both cell lines formed spheroids using scaffold-free methods. All samples retained liposarcoma characteristic, such as high level of MDM2 protein expression and MDM2 DNA amplification after being cultivated in 3D. 3D collagen samples showed higher cell viability after SAR40538 treatment than 2D models, while cells sensitive to the drug died by apoptosis or necrosis. Conclusion: Our results prompt us to extend our investigation by applying our 3D models to further oncological relevant applications, which may help address unresolved questions about dedifferentiated liposarcoma biology.

MDM2-p53 in liposarcoma: The need for targeted therapies with novel mechanisms of action

Well-differentiated and dedifferentiated liposarcomas (WDLPS and DDLPS) are rare tumors that arise from lipocytes in soft tissue. There is a high unmet need in patients with these liposarcomas given poor outcomes, particularly for DDLPS. WDLPS and DDLPS share important genetic and histological characteristics - most notably, the amplification of the 2 genes MDM2 and CDK4. Both genes are considered oncogenes because of their ability to shut down tumor suppressor pathways. There are multiple therapeutic approaches that aim to target MDM2 and CDK4 activity for the purpose of restoring intrinsic tumor suppressor cellular response and terminating oncogenesis. However, current understanding of the molecular mechanisms involved in WDLPS and DDLPS pathology is limited. In recent years, significant efforts have been made to refine and implement targeted therapy for this patient population. The use of patient-derived cell and tumor xenograft models has been an important tool for recapitulating WDLPS and DDLPS biology. These models also offer valuable insights for drug development and drug combination studies. Here we offer a review of the current understanding of WDLPS and DDLPS biology and its therapeutic implications.

Case Report: Primary low-grade dedifferentiated liposarcoma of the urinary bladder with molecular confirmation

Liposarcomas originating in the urinary bladder are extremely rare. Only six cases of bladder liposarcoma have been reported, and all have been described as myxoid liposarcomas. Notably, none of the patients underwent molecular testing. Here, we report a dedifferentiated liposarcoma (DDL) that occurred in the urinary bladder, primarily in a 69-year-old Chinese woman, with infrequent low-grade dedifferentiation. Computed tomography (CT) revealed an ill-defined solid mass in the anterior bladder wall. The patient underwent a partial bladder resection. Histologically, the tumor cells with mild-to-moderate nuclear atypia were arranged in fascicular and storiform patterns, mimicking a low-grade fibroblastic tumor. In addition, scattered small foci of typical lipoma-like well-differentiated components were identified. Immunohistochemically, the tumor tested positivity for MDM2, CDK4, and p16. Fluorescence in situ hybridization revealed MDM2 gene amplification in the neoplastic cells. Whole-exome sequencing showed that this tumor also harbored CDK4, TSPAN31, and JUN amplification. At the latest follow-up (85 months after surgery), the patient was alive, with no evidence of disease. To the best of our knowledge, this is the first example of a molecularly confirmed primary bladder liposarcoma and the first case of DDL at this site.

Extremely Rare Type of Breast Cancer-Dedifferentiated Breast Liposarcoma-Diagnosis and Treatment

Primary liposarcoma of the breast is an uncommon soft tissue malignant tumor, comprising only 0.003% of all malignant breast tumors. The main differential diagnosis of this mass consists of malignant phyllodes tumor and metaplastic breast carcinoma. The objective of this paper is to report a case of dedifferentiated breast liposarcoma, therapeutic approach and outcome. We present a case of a 79-year-old woman complaining of a large mass in her left breast which had increased in size over the last 6 months. Physical examination revealed an enlarged left breast, and a total body CT scan showed a large tumor in contact with the musculature of the anterior thoracic wall, with no metastatic lesions. The histopathology report of a fine needle biopsy described a high-grade sarcoma. The Oncological Tumor Board recommended neoadjuvant radiotherapy sessions and reevaluation by MRI and CT scans. The patient underwent radical mastectomy with latissimus dorsi myo-cutaneous flap reconstruction. The final histopathology diagnosis was a grade 3 dedifferentiated liposarcoma (FNCLCC), with certain response to radiotherapy and positive MDM2, CDK4 markers. The postoperative period was uneventful; 12 months after surgery, the follow-up CT scan showed multiple pulmonary lesions with metastatic characteristics. Liposarcoma is a very rare type of breast cancer, and the most important treatment for breast sarcoma is surgery, the role of axillary lymph node removal, chemotherapy and radiotherapy still being controversial. Considering such cases are scarce and the development of surgical guidelines is difficult, reporting any new case is crucial.

Design, synthesis, and biological evaluation of furan-bearing pyrazolo[3,4-b]pyridines as novel inhibitors of CDK2 and P53-MDM2 protein-protein interaction

The novel series of furan-bearing pyrazolo[3,4-b]pyridines were designed as cyclin-dependent kinase 2 (CDK2) inhibitors and as p53-murine double minute 2 (MDM2) inhibitors. The newly synthesized compounds were screened for their antiproliferative activity toward hepatocellular carcinoma (HepG2) and breast cancer (MCF7) cell lines. The most active compounds on both cell lines were additionally evaluated for their in vitro CDK2 inhibitory activity. Compounds 7b and 12f displayed enhanced activity (half-maximal inhibitory concentration [IC50 ] = 0.46 and 0.27 µM, respectively) in comparison to the standard roscovitine (IC50  = 1.41 ± 0.03 µM), in addition to, cell cycle arrest at S phase and G1/S transition phase in MCF7 cells treated with both compounds, respectively. Moreover, the most active spiro-oxindole derivative against MCF7 cell line, 16a, exhibited enhanced inhibitory activity against p53-MDM2 interaction in vitro (IC50  = 3.09 ± 0.12 µM) compared to nutlin, and increased the levels of both p53 and p21 by nearly fourfold in comparison to the negative control. Molecular docking studies demonstrated the plausible interaction patterns of the most potent derivatives 17b and 12f in the CDK2 binding pocket and the spiro-oxindole 16a with p53-MDM2 complex, respectively. Consequently, the new chemotypes 7b, 12f, and 16a can be presented as promising antitumor hits for further studies and optimization.

State of the Art of Pharmacological Activators of p53 in Ocular Malignancies

The pivotal role of p53 in the regulation of a vast array of cellular functions has been the subject of extensive research. The biological activity of p53 is not strictly limited to cell cycle arrest but also includes the regulation of homeostasis, DNA repair, apoptosis, and senescence. Thus, mutations in the p53 gene with loss of function represent one of the major mechanisms for cancer development. As expected, due to its key role, p53 is expressed throughout the human body including the eye. Specifically, altered p53 signaling pathways have been implicated in the development of conjunctival and corneal tumors, retinoblastoma, uveal melanoma, and intraocular melanoma. As non-selective cancer chemotherapies as well as ionizing radiation can be associated with either poor efficacy or dose-limiting toxicities in the eye, reconstitution of the p53 signaling pathway currently represents an attractive target for cancer therapy. The present review discusses the role of p53 in the pathogenesis of these ocular tumors and outlines the various pharmacological activators of p53 that are currently under investigation for the treatment of ocular malignancies.

Brightline-1: phase II/III trial of the MDM2-p53 antagonist BI 907828 versus doxorubicin in patients with advanced DDLPS

Dedifferentiated liposarcoma (DDLPS) is a rare, aggressive liposarcoma associated with poor prognosis. First-line treatment for advanced/metastatic DDLPS is systemic chemotherapy, but efficacy is poor and toxicities substantial. Most DDLPS tumors have amplification of the MDM2 gene, which encodes a negative regulator of the p53 suppressor protein. BI 907828 is a highly potent, oral MDM2-p53 antagonist that inhibits the interaction between p53 and MDM2, thereby restoring p53 activity. BI 907828 has shown promising activity in preclinical studies and in a phase Ia/Ib study in patients with solid tumors, particularly those with DDLPS. This manuscript describes the rationale and design of an ongoing multicenter, randomized, phase II/III trial (Brightline-1; NCT05218499) evaluating BI 907828 versus doxorubicin as first-line treatment for advanced DDLPS.

Three dimensional models of dedifferentiated liposarcoma cell lines: scaffold-based and scaffold-free approaches

Sarcomas are rare malignancies, the number of reports is limited, and this rarity makes further research difficult even though liposarcoma is one of major sarcomas. 2D cell culture remains an important role in establishing basic tumor biology research, but its various shortcomings and limitations are still of concern, and it is now well-accepted that the behavior of 3D-cultured cells is more reflective of in vivo cellular responses compared to 2D models. This study aimed to establish 3D cell culture of liposarcomas using two different methods: scaffold-based (Matrigel extracellular matrix [ECM] scaffold method) and scaffold-free (Ultra-low attachment [ULA] plate). Lipo246, Lipo224 and Lipo863 cell lines were cultured, and distinctive differences in structures were observed in Matrigel 3D model: Lipo224 and Lipo863 formed spheroids, whereas Lipo246 grew radially without forming spheres. In ULA plate approaches, all cell lines formed spheroids, but Lipo224 and Lipo863 spheroids showed bigger size and looser aggregation than Lipo246. Formalin fixed, paraffin embedded (FFPE) blocks were obtained from all 3D models, confirming the spheroid structures. The expression of MDM2, Ki-67 positivity and MDM2 amplification were confirmed by IHC and DNAscope™, respectively. Protein and DNA were extracted from all samples and MDM2 upregulation was confirmed by western blot and qPCR analysis. After treatment with MDM2 inhibitor SAR405838, DDLPS spheroids demonstrated different sensitivity patterns from 2D models. Taken together, we believed that 3D models would have a possibility to provide us a new predictability of efficacy and toxicity, and considered as one important process in in vitro pre-clinical phase prior to moving forward to clinical trials.

Helicobacter pylori-induced NAT10 stabilizes MDM2 mRNA via RNA acetylation to facilitate gastric cancer progression

BACKGROUND

N4-acetylcytidine (ac4C), a widespread modification in human mRNAs that is catalyzed by the N-acetyltransferase 10 (NAT10) enzyme, plays an important role in promoting mRNA stability and translation. However, the biological functions and regulatory mechanisms of NAT10-mediated ac4C were poorly defined.

METHODS

ac4C mRNA modification status and NAT10 expression levels were analyzed in gastric cancer (GC) samples and compared with the corresponding normal tissues. The biological role of NAT10-mediated ac4C and its upstream and downstream regulatory mechanisms were determined in vitro and in vivo. The therapeutic potential of targeting NAT10 in GC was further explored.

RESULTS

Here, we demonstrated that both ac4C mRNA modification and its acetyltransferase NAT10 were increased in GC, and increased NAT10 expression was associated with disease progression and poor patient prognosis. Functionally, we found that NAT10 promoted cellular G2/M phase progression, proliferation and tumorigenicity of GC in an ac4C-depedent manner. Mechanistic analyses demonstrated that NAT10 mediated ac4C acetylation of MDM2 transcript and subsequently stabilized MDM2 mRNA, leading to its upregulation and p53 downregulation and thereby facilitating gastric carcinogenesis. In addition, Helicobacter pylori (Hp) infection contributed to NAT10 induction, causing MDM2 overexpression and subsequent p53 degradation. Further investigations revealed that targeting NAT10 with Remodelin showed anti-cancer activity in GC and augmented the anti-tumor activity of MDM2 inhibitors in p53 wild-type GC.

CONCLUSIONS

These results suggest the critical role of NAT10-mediated ac4C modification in GC oncogenesis and reveal a previously unrecognized signaling cascade involving the Hp-NAT10-MDM2-p53 axis during GC development.

Targeting the MDM2-p53 pathway in dedifferentiated liposarcoma

Dedifferentiated liposarcoma (DDLPS) is an aggressive adipogenic cancer with poor prognosis. DDLPS tumors are only modestly sensitive to chemotherapy and radiation, and there is a need for more effective therapies. Genetically, DDLPS is characterized by a low tumor mutational burden and frequent chromosomal structural abnormalities including amplification of the 12q13-15 chromosomal region and the MDM2 gene, which are defining features of DDLPS. The MDM2 protein is an E3 ubiquitin ligase that targets the tumor suppressor, p53, for proteasomal degradation. MDM2 amplification or overexpression in human malignancies is associated with cell-cycle progression and worse prognosis. The MDM2-p53 interaction has thus garnered interest as a therapeutic target for DDLPS and other malignancies. MDM2 binds p53 via a hydrophobic protein interaction that is easily accessible with synthetic analogues. Multiple agents have been developed, including Nutlins such as RG7112 and small molecular inhibitors including SAR405838 and HDM201. Preclinical in vitro and animal models have shown promising results with MDM2 inhibition, resulting in robust p53 reactivation and cancer cell death. However, multiple early-phase clinical trials have failed to show a benefit with MDM2 pathway inhibition for DDLPS. Mechanisms of resistance are being elucidated, and novel inhibitors and combination therapies are currently under investigation. This review provides an overview of these strategies for targeting MDM2 in DDLPS.

Evaluation of Efficacy of Adjuvant Radiotherapy in Well-Differentiated Liposarcoma Patients with Positive Surgical Margins: A Population-based Study

Background

The use of adjuvant radiotherapy (RT) for well-differentiated liposarcoma (WD-LPS) patients with positive surgical margins is unclear. We aim to compare the overall survival (OS) and cancer-specific survival (CSS) of well-differentiated liposarcoma patients with positive surgical margins in an RT group and non-RT group.

Methods

WD-LPS patients with positive margins from 2000 to 2018 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database and divided into two groups: RT group and non-RT group. Kaplan–Meier survival analysis with the log-rank test was performed to evaluate the difference of overall survival (OS) and cancer-specific survival (CSS) between groups. Univariate and multivariate Cox proportional hazard analyses were performed to identify important prognostic factors of OS and CSS. Analyses were adjusted using propensity-score matching.

Results

We identified 2549 patients: 377 (14.79%) with RT and 2172 (85.21%) without RT. The median age was 61 years, and the median follow-up time was 68 months. The log-rank test revealed that there was no significant difference of CSS between RT and non-RT groups (P = 0.81). The 5-year and 10-year CSS were comparable (P = 0.418 and P = 0.987). Additionally, the use of RT was neither an independent prognostic factor for OS nor CSS. Age, sex, tumor site, the use of chemotherapy were independent prognostic factors for OS after propensity score matching, while race and the tumor site were independent prognostic factors for CSS.

Conclusion

Adjuvant RT had no significant improvement on OS and CSS of WD-LPS patients with positive surgical margins.

Beyond targeting amplified MDM2 and CDK4 in well differentiated and dedifferentiated liposarcomas: From promise and clinical applications towards identification of progression drivers

Well differentiated and dedifferentiated liposarcomas (WDLPS and DDLPS) are tumors of the adipose tissue poorly responsive to conventional cytotoxic chemotherapy which currently remains the standard-of-care. The dismal prognosis of the DDLPS subtype indicates an urgent need to identify new therapeutic targets to improve the patient outcome. The amplification of the two driver genes MDM2 and CDK4, shared by WDLPD and DDLPS, has provided the rationale to explore targeting the encoded ubiquitin-protein ligase and cell cycle regulating kinase as a therapeutic approach. Investigation of the genomic landscape of WD/DDLPS and preclinical studies have revealed additional potential targets such as receptor tyrosine kinases, the cell cycle kinase Aurora A, and the nuclear exporter XPO1. While the therapeutic significance of these targets is being investigated in clinical trials, insights into the molecular characteristics associated with dedifferentiation and progression from WDLPS to DDLPS highlighted additional genetic alterations including fusion transcripts generated by chromosomal rearrangements potentially providing new druggable targets (e.g. NTRK, MAP2K6). Recent years have witnessed the increasing use of patient-derived cell and tumor xenograft models which offer valuable tools to accelerate drug repurposing and combination studies. Implementation of integrated "multi-omics" investigations applied to models recapitulating WD/DDLPS genetics, histologic differentiation and biology, will hopefully lead to a better understanding of molecular alterations driving liposarcomagenesis and DDLPS progression, as well as to the identification of new therapies tailored on tumor histology and molecular profile.

Dedifferentiation in low-grade osteosarcoma: a Japanese Musculoskeletal Oncology Group (JMOG) study

BACKGROUND

Low-grade osteosarcomas, namely parosteal osteosarcoma (POS) and low-grade central osteosarcoma (LGCOS), occasionally dedifferentiate into high-grade malignancy, referred to as dedifferentiation in low-grade osteosarcoma (DLOS). This study aimed to elucidate the clinicopathologic features of DLOS, which are poorly described to date due to the extreme rarity of the disease.

METHODS

A total of 33 patients with DLOS were included. Clinical characteristics, including the diagnostic accuracy of tumor biopsy, multimodal treatments, and clinical course, were retrospectively reviewed. Univariate analysis was performed to identify prognostic factors associated with overall survival (OS) and metastasis-free survival (MFS).

RESULTS

The tumor subtypes comprised 10 cases (30.3%) of LGCOS and 23 cases (69.7%) of POS. The timing of dedifferentiation was synchronous in 25 (75.8%) and metachronous in 8 (24.2%) patients. The rates of preoperative diagnosis of DLOS were 40.0% and 65.4% for core needle biopsy and incisional biopsy, respectively. All patients underwent surgery and 25 patients received perioperative chemotherapy. Of the 13 patients who received neoadjuvant chemotherapy, 11 exhibited a poor histological response. The 5-year OS and MFS rates were 88.1% and 77.7%, respectively. Univariate analysis revealed that local recurrence was associated with poor OS (P < 0.01) and MFS (P < 0.01). Perioperative chemotherapy did not affect OS or MFS.

CONCLUSIONS

The diagnostic accuracy of tumor biopsy for DLOS was lower than that for bone sarcomas, as reported previously. In contrast to conventional osteosarcomas with high chemosensitivity, both histological responses and survival analysis revealed low efficacy of chemotherapy for DLOS.

Novel Allosteric Mechanism of Dual p53/MDM2 and p53/MDM4 Inhibition by a Small Molecule

Restoration of the p53 tumor suppressor for personalised cancer therapy is a promising treatment strategy. However, several high-affinity MDM2 inhibitors have shown substantial side effects in clinical trials. Thus, elucidation of the molecular mechanisms of action of p53 reactivating molecules with alternative functional principle is of the utmost importance. Here, we report a discovery of a novel allosteric mechanism of p53 reactivation through targeting the p53 N-terminus which promotes inhibition of both p53/MDM2 (murine double minute 2) and p53/MDM4 interactions. Using biochemical assays and molecular docking, we identified the binding site of two p53 reactivating molecules, RITA (reactivation of p53 and induction of tumor cell apoptosis) and protoporphyrin IX (PpIX). Ion mobility-mass spectrometry revealed that the binding of RITA to serine 33 and serine 37 is responsible for inducing the allosteric shift in p53, which shields the MDM2 binding residues of p53 and prevents its interactions with MDM2 and MDM4. Our results point to an alternative mechanism of blocking p53 interaction with MDM2 and MDM4 and may pave the way for the development of novel allosteric inhibitors of p53/MDM2 and p53/MDM4 interactions.

The Molecular Biology of Soft Tissue Sarcomas: Current Knowledge and Future Perspectives

Simple Summary

Over the past 20 years, significant advances in the field of genetics and molecular biology have led to the dismantlement of multiple subtypes of sarcomas. As a result, molecular approaches nowadays play a critical role in the diagnosis, prognostic classification, and therapeutic management of numerous mesenchymal tumor subtypes. This review of the current literature illustrates the main uses of molecular biology in the field of soft tissue sarcomas and the future challenges that remain to be addressed.

Abstract

Soft tissue sarcomas are malignant tumors of mesenchymal origin, encompassing a large spectrum of entities that were historically classified according to their histological characteristics. Over the last decades, molecular biology has allowed a better characterization of these tumors, leading to the incorporation of multiple molecular features in the latest classification of sarcomas as well as to molecularly-guided therapeutic strategies. This review discusses the main uses of molecular biology in current practice for the diagnosis and treatment of soft tissue sarcomas, in addition to perspectives for this rapidly evolving field of research.

Update of Pediatric Lipomatous Lesions: A Clinicopathological, Immunohistochemical and Molecular Overview

Lipomatous neoplasms are a rare entity in the pediatric population, comprising less than 10% of soft tissue tumors in the first two decades of life. Some characteristics of pediatric adipocytic tumors are analogous to their adult counterparts, some pediatric lipomatous lesions however harbor unique features. In recent years, there have been significant advances in the understanding of the pathogenesis and hence in the classification and treatment of pediatric adipocytic tumors. This literature-based article will provide a review of the presently known clinicopathological, immunohistochemical and molecular features of pediatric lipomatous lesions.

Targetable Pathways in the Treatment of Retroperitoneal Liposarcoma

Liposarcoma (LPS) is the most prevalent soft tissue sarcoma histological subtype. When it occurs in the abdomen the overall survival rate is as low as 10% at 10 years and is fraught with high rates of recurrence, particularly for the more aggressive dedifferentiated subtype. Surgery remains the mainstay of treatment. Systemic therapies for the treatment of metastatic or unresectable disease have low response rates. Deep understanding of well-differentiated and de-differentiated LPS (WDLPS and DDLPS, respectively) oncologic drivers is necessary for the development of new efficacious targeted therapies for the management of this disease. This review discusses the current treatments under evaluation for retroperitoneal DDLPS and the potential targetable pathways in DDLPS.

Noncanonical roles of p53 in cancer stemness and their implications in sarcomas

Impairment of the prominent tumor suppressor p53, well known for its canonical role as the "guardian of the genome", is found in almost half of human cancers. More recently, p53 has been suggested to be a crucial regulator of stemness, orchestrating the differentiation of embryonal and adult stem cells, suppressing reprogramming into induced pluripotent stem cells, or inhibiting cancer stemness (i.e., cancer stem cells, CSCs), which underlies the development of therapy-resistant tumors. This review addresses these noncanonical roles of p53 and their implications in sarcoma initiation and progression. Indeed, dysregulation of p53 family proteins is a common event in sarcomas and is associated with poor survival. Additionally, emerging studies have demonstrated that loss of wild-type p53 activity hinders the terminal differentiation of mesenchymal stem cells and leads to the development of aggressive sarcomas. This review summarizes recent findings on the roles of aberrant p53 in sarcoma development and stemness and further describes therapeutic approaches to restore normal p53 activity as a promising anti-CSC strategy to treat refractory sarcomas.

Pediatric liposarcoma: A case series and literature review

Liposarcoma is arare soft tissue sarcoma in children. While prognosis, clinical behavior, and response to therapy among the various histologic subtypes are well described in adults, data in children are limited. Here, we describe our experience treating 14 children with liposarcoma at a large, academic pediatric center and review the available pediatric literature. This comprehensive report adds treatment, survival, and genomic data to pediatric liposarcoma literature.

MI-773, a breaker of the MDM2/p53 axis, exhibits anticancer effects in neuroblastoma via downregulation of INSM1

Neuroblastoma (NB) is a common pediatric malignancy associated with poor outcomes. Recent studies have shown that murine double minute2 homolog (MDM2) protein inhibitors are promising anticancer agents. MI-773 is a novel and specific antagonist of MDM2, however, the molecular mechanism of its anti-NB activity remains unclear. NB cell viability was measured by Cell Counting Kit-8 assay following MI-773 treatment. Cell cycle progression was analyzed using PI staining and apoptosis was assessed using Annexin V/PI staining. The molecular mechanisms by which MI-773 exerted its effects were investigated using a microarray. The results showed that disturbance of the MDM2/p53 axis by MI-773 resulted in potent suppression of proliferation, induction of apoptosis and cell cycle arrest in NB cells. In addition, microarray analysis showed that MI-773 led to significant downregulation of genes involved in the G₂/M phase checkpoint and upregulation of hallmark gene associated with the p53 pathway. Meanwhile, knockdown of insulinoma-associated 1 decreased proliferation and increased apoptosis of NB cells. In conclusion, the present study demonstrated that MI-773 exhibited high selectivity and blockade affinity for the interaction between MDM2 and TP53 and may serve as a novel strategy for the treatment of NB.

Expression of FRS2 in atypical lipomatous tumor/well-differentiated liposarcoma and dedifferentiated liposarcoma: an immunohistochemical analysis of 182 cases with genetic data

Background

The fibroblast growth factor receptor substrate 2 (FRS2) gene is located close to MDM2 and CDK4 within the 12q13-15 chromosomal region. FRS2 gene was recently found to be consistently amplified in atypical lipomatous tumor (ALT)/well-differentiated liposarcoma (WDL) and dedifferentiated liposarcoma (DDL), suggesting the detection of FRS2 amplification could be a diagnostic tool for ALT/WDL/DDLs. However, the expression of FRS2 protein and diagnostic value of FRS2 immunohistochemistry (IHC) has not been evaluated in a large cohort of ALT/WDL/DDLs.

Methods

A SNOMED search of hospital surgical pathology files from January 2007 to July 2020 identified 182 ALT/WDL/DDLs with available materials. FRS2 fluorescence in situ hybridization (FISH) and IHC were performed on 182 ALT/WDL/DDLs and 64 control samples. The expression of FRS2 was also compared with that of classic immunomarkers (MDM2 and CDK4) of this tumor entity.

Results

This study included 91 ALT/WDLs and 91 DDLs. The FISH results showed 172 of 182 (94.5%) cases were FRS2-amplified, and 10 cases were FRS2-nonamplified. Immunostaining results showed 171 (94.0%) ALT/WDL/DDLs were positive for FRS2 and 11 cases (6.0%) were FRS2-immunonegative. In 172 FRS2-amplified cases, 166 (96.5%) were FRS2-immunopositive, and 6 (3.5%) were negative. Among 10 FRS2-nonamplified ALT/WDL/DDL cases, 5 cases were FRS2-immunonegative, and 5 tumors displayed 1+ staining for this marker. In 64 control cases, none of them exhibited FRS2 amplification. Forty-seven (73.5%) control cases were negative for FRS2 immunostaining, while 17 cases (26.5%) were FRS2-immunopositive. Fifteen of these false positive samples (15/17, 88.2%) showed 1+ positivity and only 2 cases (2/17, 11.8%) displayed 2+ positivity. In ALT/WDL/DDLs, the sensitivity of FRS2 immunostaining was slightly lower than MDM2 (FRS2 vs. MDM2: 94.0% vs 100.0%) and CDK4 (FRS2 vs. CDK4: 94.0% vs 97.0%). However, the specificity of FRS2 (73.5%) was slightly higher than that of MDM2 (67.8%) and CDK4 (64.4%).

Conclusion

This study indicated that FRS2 IHC had relatively good consistency with FRS2 FISH, suggesting that FRS2 immunostaining could be utilized as an additional screening tool for the diagnosis of ALT/WDL/DDL. It must be emphasized that MDM2/CDK4/FRS2 especially MDM2 FISH remains the gold standard and the most recommended method to diagnose this entity.

TP53 in Biology and Treatment of Osteosarcoma

The TP53 gene is mutated in 50% of human tumors. Oncogenic functions of mutant TP53 maintain tumor cell proliferation and tumor growth also in osteosarcomas. We collected data on TP53 mutations in patients to indicate which are more common and describe their role in in vitro and animal models. We also describe animal models with TP53 dysfunction, which provide a good platform for testing the potential therapeutic approaches. Finally, we have indicated a whole range of pharmacological compounds that modulate the action of p53, stabilize its mutated versions or lead to its degradation, cause silencing or, on the contrary, induce the expression of its functional version in genetic therapy. Although many of the described therapies are at the preclinical testing stage, they offer hope for a change in the approach to osteosarcoma treatment based on TP53 targeting in the future.

Targeted and immuno-based therapies in sarcoma: mechanisms and advances in clinical trials

Sarcomas represent a distinct group of rare malignant tumors with high heterogeneity. Limited options with clinical efficacy for the metastatic or local advanced sarcoma existed despite standard therapy. Recently, targeted therapy according to the molecular and genetic phenotype of individual sarcoma is a promising option. Among these drugs, anti-angiogenesis therapy achieved favorable efficacy in sarcomas. Inhibitors targeting cyclin-dependent kinase 4/6, poly-ADP-ribose polymerase, insulin-like growth factor-1 receptor, mTOR, NTRK, metabolisms, and epigenetic drugs are under clinical evaluation for sarcomas bearing the corresponding signals. Immunotherapy represents a promising and favorable method in advanced solid tumors. However, most sarcomas are immune "cold" tumors, with only alveolar soft part sarcoma and undifferentiated pleomorphic sarcoma respond to immune checkpoint inhibitors. Cellular therapies with TCR-engineered T cells, chimeric antigen receptor T cells, tumor infiltrating lymphocytes, and nature killer cells transfer show therapeutic potential. Identifying tumor-specific antigens and exploring immune modulation factors arguing the efficacy of these immunotherapies are the current challenges. This review focuses on the mechanisms, advances, and potential strategies of targeted and immune-based therapies in sarcomas.

Biology and Management of Dedifferentiated Liposarcoma: State of the Art and Perspectives

Dedifferentiated liposarcoma (DDL) is defined as the transition from well-differentiated liposarcoma (WDL)/atypical lipomatous tumor (ALT) to non-lipogenic sarcoma, which arises mostly in the retroperitoneum and deep soft tissue of proximal extremities. It is characterized by a supernumerary ring and giant marker chromosomes, both of which contain amplified sequences of 12q13-15 including murinedouble minute 2 (MDM2) and cyclin-dependent kinase 4 (CDK4) cell cycle oncogenes. Detection of MDM2 (and/or CDK4) amplification serves to distinguish DDL from other undifferentiated sarcomas. Recently, CTDSP1/2-DNM3OS fusion genes have been identified in a subset of DDL. However, the genetic events associated with dedifferentiation of WDL/ALT remain to be clarified. The standard treatment for localized DDL is surgery, with or without radiotherapy. In advanced disease, the standard first-line therapy is an anthracycline-based regimen, with either single-agent anthracycline or anthracycline in combination with the alkylating agent ifosfamide. Unfortunately, this regimen has not necessarily led to a satisfactory clinical outcome. Recent advances in the understanding of the pathogenesis of DDL may allow for the development of more-effective innovative therapeutic strategies. This review provides an overview of the current knowledge on the clinical presentation, pathogenesis, histopathology and treatment of DDL.

Chalcones as Promising Antitumor Agents by Targeting the p53 Pathway: An Overview and New Insights in Drug-Likeness

The p53 protein is one of the most important tumor suppressors that are frequently inactivated in cancer cells. This inactivation occurs either because the TP53 gene is mutated or deleted, or due to the p53 protein inhibition by endogenous negative regulators, particularly murine double minute (MDM)2. Therefore, the reestablishment of p53 activity has received great attention concerning the discovery of new cancer therapeutics. Chalcones are naturally occurring compounds widely described as potential antitumor agents through several mechanisms, including those involving the p53 pathway. The inhibitory effect of these compounds in the interaction between p53 and MDM2 has also been recognized, with this effect associated with binding to a subsite of the p53 binding cleft of MDM2. In this work, a literature review of natural and synthetic chalcones and their analogues potentially interfering with p53 pathway is presented. Moreover, in silico studies of drug-likeness of chalcones recognized as p53-MDM2 interaction inhibitors were accomplished considering molecular descriptors, biophysiochemical properties, and pharmacokinetic parameters in comparison with those from p53-MDM2 in clinical trials. With this review, we expect to guide the design of new and more effective chalcones targeting the p53 pathway.

The p53 pathway in vasculature revisited: A therapeutic target for pathological vascular remodeling?

Pathological vascular remodeling contributes to the development of restenosis following intraluminal interventions, transplant vasculopathy, and pulmonary arterial hypertension. Activation of the tumor suppressor p53 may counteract vascular remodeling by inhibiting aberrant proliferation of vascular smooth muscle cells and repressing vascular inflammation. In particular, the development of different lines of small-molecule p53 activators ignites the hope of treating remodeling-associated vascular diseases by targeting p53 pharmacologically. In this review, we discuss the relationships between p53 and pathological vascular remodeling, and summarize current experimental data suggesting that drugging the p53 pathway may represent a novel strategy to prevent the development of vascular remodeling.

[New data on the molecular biology of soft tissue sarcoma]

Sarcoma consists in a group of rare malignant tumours of mesenchymal origin characterized by their vast clinical, pathological and biological heterogeneity. The pathological diagnosis of sarcoma relies classically of the differentiation features of tumour cells, with dozens of different tumour subtypes described in the last international classifications. Over the last decades, the advances in the development of new techniques of molecular biology have led to a major complexification of sarcoma classification, with the identification of multiple and specific molecular alterations that have led to significant changes for patients diagnostic, prognostic and therapeutic management. This review aims at giving an overview on the current knowledge of the molecular biology of soft tissue sarcoma, and emphasizes on their consequences for the daily management of patients.

Update on genomic and molecular landscapes of well-differentiated liposarcoma and dedifferentiated liposarcoma

Well-differentiated liposarcoma (WDLPS) is the most frequent subtype of liposarcoma and may transform into dedifferentiated liposarcoma (DDLPS) which is a more aggressive subtype. Retroperitoneal lesions of WDLPS/DDLPS tend to recur repeatedly due to incomplete resections, and adjuvant chemotherapy and radiotherapy have little effect on patient survival. Consequently, identifying therapeutic targets and developing targeted drugs is critical for improving the outcome of WDLPS/DDLPS patients. In this review, we summarised the mutational landscape of WDLPS/DDLPS from recent studies focusing on potential oncogenic drivers and the development of molecular targeted drugs for DDLPS. Due to the limited number of studies on the molecular networks driving WDLPS to DDLPS development, we looked at other dedifferentiation-related tumours to identify potential parallel mechanisms that could be involved in the dedifferentiation process generating DDLPS.

MDM2 Amplified Sarcomas: A Literature Review

Murine Double Minute Clone 2, located at 12q15, is an oncogene that codes for an oncoprotein of which the association with p53 was discovered 30 years ago. The most important function of MDM2 is to control p53 activity; it is in fact the best documented negative regulator of p53. Mutations of the tumor suppressor gene p53 represent the most frequent genetic change in human cancers. By overexpressing MDM2, cancer cells have another means to block p53. The sarcomas in which MDM2 amplification is a hallmark are well-differentiated liposarcoma/atypical lipomatous tumor, dedifferentiated liposarcoma, intimal sarcoma, and low-grade osteosarcoma. The purpose of this review is to summarize the typical clinical, histopathological, immunohistochemical, and genetic features of these tumors.

Design, synthesis, and biological evaluation of nitroisoxazole-containing spiro[pyrrolidin-oxindole] derivatives as novel glutathione peroxidase 4/mouse double minute 2 dual inhibitors that inhibit breast adenocarcinoma cell proliferation

A series of highly active CF₃-containing 3'-(nitroisoxazole)spiro[pyrrolidin-3,2'-oxindoles] were synthesized and found to be novel glutathione peroxidase 4 (GPX4)/mouse double minute 2 (MDM2) dual inhibitors. Bioactive spirooxindole and isoxazole skeletons were combined, and the resulting compounds exhibited strong activities against both targets. In particular, compound 3d displayed excellent activity in the suppression of MDM2-mediated degradation of p53, as well as levels of GPX4, in MCF-7 breast cancer cells. Moreover, 3d also exhibited inhibitory effects on MDM2 and GPX4 in MCF-7 xenograft model to trigger ferroptotic and apoptotic cell death in in vivo experiments, which was consistent with the results of in vitro experiments.

Cross-flow microfiltration for isolation, selective capture and release of liposarcoma extracellular vesicles

We present a resource‐efficient approach to fabricate and operate a micro‐nanofluidic device that uses cross‐flow filtration to isolate and capture liposarcoma derived extracellular vesicles (EVs). The isolated extracellular vesicles were captured using EV‐specific protein markers to obtain vesicle enriched media, which was then eluted for further analysis. Therefore, the micro‐nanofluidic device integrates the unit operations of size‐based separation with CD63 antibody immunoaffinity‐based capture of extracellular vesicles in the same device to evaluate EV‐cargo content for liposarcoma. The eluted media collected showed ∼76% extracellular vesicle recovery from the liposarcoma cell conditioned media and ∼32% extracellular vesicle recovery from dedifferentiated liposarcoma patient serum when compared against state‐of‐art extracellular vesicle isolation and subsequent quantification by ultracentrifugation. The results reported here also show a five‐fold increase in amount of critical liposarcoma‐relevant extracellular vesicle cargo obtained in 30 min presenting a significant advance over existing state‐of‐art.

Multi-Layer Micro-Nanofluidic Device for Isolation and Capture of Extracellular Vesicles Derived from Liposarcoma Cell Conditioned Media

We report on isolation, capture, and subsequent elution for analysis of extracellular vesicles derived from human liposarcoma cell conditioned media, using a multi-layer micro-nanofluidic device operated with tangential flow separation. Our device integrates size-based separation followed by immunoaffinity-based capture of extracellular vesicles in the same device. For liposarcomas, this is the first report on isolating, capturing, and then eluting the extracellular vesicles using a micro-nanofluidic device. The results show a significantly higher yield of the eluted extracellular vesicles (~84%) compared to the current methods of ultracentrifugation (~6%) and ExoQuick-based separations (~16%).

Targeting p53-MDM2 Interaction Using Small Molecule Inhibitors and the Challenges Needed to be Addressed

MDM2 protein is the core negative regulator of p53 that maintains the cellular levels of p53 at a low level in normal cells. Mutation of the TP53 gene accounts for 50% of all human cancers. In the remaining malignancies with wild-type TP53, p53 function is inhibited through other mechanisms. Recently, synthetic small molecule inhibitors have been developed which target a small hydrophobic pocket on MDM2 to which p53 normally binds. Given that MDM2-p53 antagonists have been undergoing clinical trials for different types of cancer, this review illustrates different aspects of these new cancer targeted therapeutic agents with the focus on the major advances in the field. It emphasizes on the p53 function, regulation of p53, targeting of the p53-MDM2 interaction for cancer therapy, and p53-dependent and -independent effects of inhibition of p53-MDM2 interaction. Then, representatives of small molecule MDM2-p53 binding antagonists are introduced with a focus on those entered into clinical trials. Furthermore, the review discusses the gene signatures in order to predict sensitivity to MDM2 antagonists, potential side effects and the reasons for the observed hematotoxicity, mechanisms of resistance to these drugs, their evaluation as monotherapy or in combination with conventional chemotherapy or with other targeted therapeutic agents. Finally, it highlights the certainly intriguing questions and challenges which would be addressed in future studies.

MDM2-Dependent Rewiring of Metabolomic and Lipidomic Profiles in Dedifferentiated Liposarcoma Models

Dedifferentiated liposarcoma (DDLPS) is an aggressive mesenchymal cancer marked by amplification of MDM2, an inhibitor of the tumor suppressor TP53. DDLPS patients with higher MDM2 amplification have lower chemotherapy sensitivity and worse outcome than patients with lower MDM2 amplification. We hypothesized that MDM2 amplification levels may be associated with changes in DDLPS metabolism. Six patient-derived DDLPS cell line models were subject to comprehensive metabolomic (Metabolon) and lipidomic (SCIEX 5600 TripleTOF-MS) profiling to assess associations with MDM2 amplification and their responses to metabolic perturbations. Comparing metabolomic profiles between MDM2 higher and lower amplification cells yielded a total of 17 differentially abundant metabolites across both panels (FDR < 0.05, log2 fold change < 0.75), including ceramides, glycosylated ceramides, and sphingomyelins. Disruption of lipid metabolism through statin administration resulted in a chemo-sensitive phenotype in MDM2 lower cell lines only, suggesting that lipid metabolism may be a large contributor to the more aggressive nature of MDM2 higher DDLPS tumors. This study is the first to provide comprehensive metabolomic and lipidomic characterization of DDLPS cell lines and provides evidence for MDM2-dependent differential molecular mechanisms that are critical factors in chemoresistance and could thus affect patient outcome.

Inhibition of p53 inhibitors: progress, challenges and perspectives

p53 is the major tumor suppressor and the most frequently inactivated gene in cancer. p53 could be disabled either by mutations or by upstream negative regulators, including, but not limited to MDM2 and MDMX. p53 activity is required for the prevention as well as for the eradication of cancers. Restoration of p53 activity in mouse models leads to the suppression of established tumors of different origin. These findings provide a strong support to the anti-cancer strategy aimed for p53 reactivation. In this review, we summarize recent progress in the development of small molecules, which restore the tumor suppressor function of wild-type p53 and discuss their clinical advance. We discuss different aspects of p53-mediated response, which contribute to suppression of tumors, including non-canonical p53 activities, such as regulation of immune response. While targeting p53 inhibitors is a very promising approach, there are certain limitations and concerns that the intensive research and clinical evaluation of compounds will hopefully help to overcome.

A review of retroperitoneal liposarcoma genomics

Retroperitoneal liposarcomas are rare tumours that carry a poorer prognosis than their extremity counterparts. Within their subtypes - well differentiated (WDL), dedifferentiated (DDL), myxoid (MLS) and pleomorphic (PLS) - they exhibit a diverse genomic landscape. With recent advances in next generation sequencing, the number of studies exploring this have greatly increased. The recent literature has deepened our understanding of the hallmark MDM2/CDK4 amplification in WDL/DDL and addressed concerns about toxicity and resistance when targeting this. The FUS-DDIT3 fusion gene remains the primary focus of interest in MLS with additional potential targets described. Whole genome sequencing has driven identification of novel genes and pathways implicated in WDL/DDL outside of the classic 12q13-15 amplicon. Due to their rarity; anatomical location and histologic subtype are infrequently mentioned when reporting the results of these studies. Reports can include non-adipogenic or extremity tumours, making it difficult to draw specific retroperitoneal conclusions. This narrative review aims to provide a summary of retroperitoneal liposarcoma genomics and the implications for therapeutic targeting.

Targeting Mouse Double Minute 2: Current Concepts in DNA Damage Repair and Therapeutic Approaches in Cancer

Defects in DNA damage repair may cause genome instability and cancer development. The tumor suppressor gene p53 regulates cell cycle arrest to allow time for DNA repair. The oncoprotein mouse double minute 2 (MDM2) promotes cell survival, proliferation, invasion, and therapeutic resistance in many types of cancer. The major role of MDM2 is to inhibit p53 activity and promote its degradation. In this review, we describe the influence of MDM2 on genomic instability, the role of MDM2 on releasing p53 and binding DNA repair proteins to inhibit repair, and the regulation network of MDM2 including its transcriptional modifications, protein stability, and localization following DNA damage in genome integrity maintenance and in MDM2-p53 axis control. We also discuss p53-dependent and p53 independent oncogenic function of MDM2 and the outcomes of clinical trials that have been used with clinical inhibitors targeting p53-MDM2 to treat certain cancers.

Recent Synthetic Approaches towards Small Molecule Reactivators of p53

The tumor suppressor protein p53 is often called "the genome guardian" and controls the cell cycle and the integrity of DNA, as well as other important cellular functions. Its main function is to trigger the process of apoptosis in tumor cells, and approximately 50% of all cancers are related to the inactivation of the p53 protein through mutations in the TP53 gene. Due to the association of mutant p53 with cancer therapy resistance, different forms of restoration of p53 have been subject of intense research in recent years. In this sense, this review focus on the main currently adopted approaches for activation and reactivation of p53 tumor suppressor function, focusing on the synthetic approaches that are involved in the development and preparation of such small molecules.

Precision Medicine in Soft Tissue Sarcoma Treatment

Soft tissue sarcoma (STS) is a rare component of malignant diseases. STS includes various histological subtypes, and there are some important differences among the different histological subtypes regarding the mutation profile and sensitivity to antitumor agents. Many clinical trials of STS incorporating many different histological subtypes in various populations have been conducted; it is difficult to compare the findings and make conclusions about clinical efficacy. Targeted therapies focusing on specific histological subtypes and precision therapy focusing on the specific genetic mutation(s) of each STS patient are being investigated. Since STS patients are a small population, new clinical trial designs are required to evaluate and establish new targeted therapies for each histological subtype that has a limited number of patients, and preclinical investigations are needed to detect targetable mutations. Now that cancer genome profiling is used in clinical practice, it is urgently necessary to connect the genome profiling data obtained in clinical settings to the optimal clinical treatment strategies. Herein we review the development and challenges of precision therapy in the management of STS patients.

The genomics of undifferentiated sarcoma of soft tissue: Progress, challenges and opportunities

Undifferentiated sarcoma of soft tissue (USTS) are aggressive sarcomas that remain a diagnosis of exclusion and show extreme genomic complexity. Many advances in diagnostic criteria have resulted in several revisions in the definition of this rare cancer type. Recent sequencing efforts have illuminated the nature of the genome complexity and have revealed extensive copy number heterogeneity and multiple evolutionary patterns of development. This review places these recent advances into their historical and translational context and covers the changes in nomenclature, molecular classification, and the promise of personalised medicine.

Inhibition of histone deacetylase 2 reduces MDM2 expression and reduces tumor growth in dedifferentiated liposarcoma

Dedifferentiated liposarcoma (DDLPS) is a highly morbid mesenchymal tumor characterized and driven by genomic amplification of the MDM2 gene. Direct inhibition of MDM2 has shown promise pre-clinically, but has yet to be validated in clinical trials. Early in vitro studies have demonstrated that pan-histone deacetylase (HDAC) inhibition may have anti-MDM2 effects. Here we present in silico, in vitro, and mouse xenograft studies that suggest that specifically targeting HDAC2 reduces MDM2 expression and has anti-tumor affects in DDLPS. Two independent datasets, The Cancer Genome Atlas (TCGA; n = 58) and the Memorial Sloan-Kettering Cancer Center Dataset (MSKCC; n = 63), were used to identify the co-expression between class I HDACs and MDM2, and their clinical impact. HDAC2 was highly co-expressed with MDM2 (TCGA: Spearman’s coefficient = 0.29, p = 0.03; MSKCC: Spearman’s coefficient = 0.57, p < 0.001). As both a continuous and dichotomous predictor, elevated HDAC2 expression was associated with worsened disease-free survival in the TCGA (Continuous: Hazard-ratio (HR) 1.7; 95% Confidence Interval (95%CI) 0.97–2.9; p = 0.06; Dichotomous: HR 7.1, 95%CI 2.5–19.8, p < 0.001) and distant recurrence-free survival in the MSKCC (Continuous: HR 2.2; 95%CI 1.1–4.8; p = 0.04; Dichotomous: HR 2.8, 95%CI 1.2–6.4, p = 0.02). In vitro, treatment of DDLPS cell lines with the HDAC inhibitors MI-192 (HDAC2/3 inhibitor) or romidepsin (HDAC1/2 inhibitor) reduced MDM2 expression and induced apoptosis. In a murine DDLPS xenograft model, romidepsin reduced tumor growth and lowered tumor MDM2 expression. RNA-sequencing of romidepsin treated mouse tumors demonstrated markers of TP53 reactivation. Taken together, our data supports the hypothesis that targeting HDAC2 may represent a potential strategy to modulate MDM2 expression in DDLPS.

MDM2 Derived from Dedifferentiated Liposarcoma Extracellular Vesicles Induces MMP2 Production from Preadipocytes

Dedifferentiated liposarcoma (DDLPS) is frequently diagnosed late, and patients typically respond poorly to treatments. DDLPS is molecularly characterized by wild-type p53 and amplification of the MDM2 gene, which results in overexpression of MDM2 protein, a key oncogenic process in DDLPS. In this study, we demonstrate that extracellular vesicles derived from patients with DDLPS or from DDLPS cell lines are carriers of MDM2 DNA that can be transferred to preadipocytes, a major and ubiquitous cellular component of the DDLPS tumor microenvironment, leading to impaired p53 activity in preadipocytes and increased proliferation, migration, and production of matrix metalloproteinase 2; treatment with MDM2 inhibitors repressed these effects. Overall, these findings indicate that MDM2 plays a crucial role in DDLPS by enabling cross-talk between tumor cells and the surrounding microenvironment and that targeting vesicular MDM2 could represent a therapeutic option for treating DDLPS. SIGNIFICANCE: Extracellular vesicles derived from dedifferentiated liposarcoma cells induce oncogenic properties in preadipocytes.

TP53 in bone and soft tissue sarcomas

Genomic and functional study of existing and emerging sarcoma targets, such as fusion proteins, chromosomal aberrations, reduced tumor suppressor activity, and oncogenic drivers, is broadening our understanding of sarcomagenesis. Among these mechanisms, the tumor suppressor p53 (TP53) plays significant roles in the suppression of bone and soft tissue sarcoma progression. Although mutations in TP53 were thought to be relatively low in sarcomas, modern techniques including whole-genome sequencing have recently illuminated unappreciated alterations in TP53 in osteosarcoma. In addition, oncogenic gain-of-function activities of missense mutant p53 (mutp53) have been reported in sarcomas. Moreover, new targeting strategies for TP53 have been discovered: restoration of wild-type p53 (wtp53) activity through inhibition of TP53 negative regulators, reactivation of the wtp53 activity from mutp53, depletion of mutp53, and targeting of vulnerabilities in cells with TP53 deletions or mutations. These discoveries enable development of novel therapeutic strategies for therapy-resistant sarcomas. We have outlined nine bone and soft tissue sarcomas for which TP53 plays a crucial tumor suppressive role. These include osteosarcoma, Ewing sarcoma, chondrosarcoma, rhabdomyosarcoma (RMS), leiomyosarcoma (LMS), synovial sarcoma, liposarcoma (LPS), angiosarcoma, and undifferentiated pleomorphic sarcoma (UPS).

Virtual Screening Based on Ensemble Docking Targeting Wild-Type p53 for Anticancer Drug Discovery

The tumor-suppressor function of p53 makes it an attractive drug target. Efforts were mostly put on stabilization of the functional p53 or reactivation of mutated p53. Previous studies have shown that small molecules targeting Loop1/Sheet3 (L1/S3) can reactivate the R175H-p53 and stabilize p53 in vitro. Since the L1/S3 pocket is shared by the mutate and the wild type (WT) p53, virtual screening is introduced to identify natural products targeting the L1/S3 of WT p53. Considering the high flexibility of Loop1, ensemble docking method is utilized for different clusters of the L1/S3. Seven conformations were chosen for docking. As one of the 181 selected candidates, torilin not only improved p53 activity, but also increased p21 protein expression level, which lies downstream of p53, therefore suppressing HCT116 cancer cell growth. Torilin may covalently bind to Cys124 of p53 by 2-methyl-2-butenal (2M2B) group, as torilin derivatives, which do not contain the 2M2B group, were not able to increase the p53 transcription activity. In conclusion, this study demonstrated that L1/S3 of WT-p53 is a druggable pocket, and torilin has a potential cytotoxicity through activating the p53 pathway.

Anti-tumor activity of the MDM2-TP53 inhibitor BI-907828 in dedifferentiated liposarcoma patient-derived xenograft models harboring MDM2 amplification

PURPOSE

Dedifferentiated liposarcoma (DDLPS) is a soft tissue malignancy characterized by amplification of the mouse double minute 2 homolog (MDM2) gene. MDM2 is a negative regulator of tumor protein 53 (TP53). We tested the in vivo efficacy of BI-907828, a small molecule inhibitor of the MDM2-TP53 interaction, in two DDLPS patient-derived xenografts (PDX).

METHODS

Partially immunodeficient mice were bilaterally engrafted with UZLX-STS3 (n = 24) and UZLX-STS5 (n = 24) human DDLPS tissue harboring MDM2 amplifications. Mice were grouped as follows: (a) vehicle (0.5% hydroxyethylcellullose) 10 ml/kg daily per os (p.o.); (b) doxorubicin 5 mg/kg weekly intraperitoneally (i.p.); (c) BI-907828 2.5 mg/kg daily p.o. and (d) BI-907828 10 mg/kg daily p.o. The treatment lasted for 15 days, all mice treated with BI-907828 were followed for 37 days post-treatment. Efficacy was assessed by tumor volume and histopathological evaluation.

RESULTS

The 15-day treatment with 2.5 mg/kg and 10 mg/kg BI-907828 significantly inhibited tumor growth in UZLX-STS5 and -STS3 (p < 0.0001 compared to control for both models). All UZLX-STS5 and -STS3 tumors treated with BI-907828 decreased in size during treatment, and BI-907828-treated UZLX-STS5 tumors even disappeared completely. During the follow-up period, no tumor regrowth was observed in the UZLX-STS5 model and both doses of BI-907828 led to a pathological complete response, whereas a dose-dependent regrowth was seen in the UZLX-STS3 model.

CONCLUSION

BI-907828 showed significant anti-tumor activity in DDLPS PDX harboring MDM2 amplifications, providing a strong rationale for early clinical testing of BI-907828 in a DDLPS patient population.

The past, present and future of potential small-molecule drugs targeting p53-MDM2/MDMX for cancer therapy

The p53 gene, a well-known tumor suppressor gene, plays a crucial role in cell cycle regulation, DNA repair, cell differentiation, and apoptosis. MDM2 exerts p53-dependent activity mainly by binding to p53 protein to form MDM2-p53 negative feedback loop. In addition, MDM2 is involved in a number of pathways that regulate cell proliferation and apoptosis, playing a p53-independent role. The p53 binding domain of MDMX bind to p53 transcriptional activation domain, inhibiting the transcriptional activity of p53 on its downstream genes, but does not mediate the degradation of p53. The anti-tumor effect is exerted by inhibiting the interaction between the MDM2/MDMX protein and the p53 protein by a small-molecule or by restoring the activity of the p53 protein. This review describes in the structural features, biological functions and mechanisms of p53-MDM2/MDMX, and summarizes small-molecule targeting p53-MDM2/MDMX.

Degree of MDM2 Amplification Affects Clinical Outcomes in Dedifferentiated Liposarcoma

BACKGROUND

Dedifferentiated liposarcomas (DDLPS) are mesenchymal tumors associated with universally poor response to treatment. Genomic amplification of murine double minute 2 (MDM2) is used as a diagnostic biomarker; however, no established biomarkers exist to guide DDLPS treatment. In the largest study of its kind, we report that the extent of MDM2 amplification, not simply the presence of MDM2 amplification, may be biologically important to the actions of DDLPS.

PATIENTS AND METHODS

The distribution of MDM2 amplification in DDLPS was assessed using data from a commercial sequencing laboratory (n = 642) and The Cancer Genome Atlas (n = 57). Data from two retrospective clinical trials (n = 15, n = 16) and one prospective clinical trial (n = 25) were used to test MDM2's utility as a clinical biomarker. in vitro and in vivo assessments were conducted in DDLPS cell lines.

RESULTS

Genomic MDM2 amplification follows a highly reproducible log-normal distribution. In patients with DDLPS treated with complete tumor resection, elevated MDM2 was associated with shortened time to recurrence as measured by genomic amplification (p = .003) and mRNA expression (p = .04). In patients requiring systemic therapy, higher MDM2 amplification was associated with reduced overall survival (p = .04). Doxorubicin treatment of DDLPS cells in vitro demonstrated variable sensitivity based on baseline MDM2 levels, and doxorubicin treatment elevated MDM2 expression. In vivo, treatment with doxorubicin followed by an MDM2 inhibitor improved doxorubicin sensitivity.

CONCLUSION

MDM2 amplification levels in DDLPS follow a reproducible distribution and are associated with clinical outcomes and drug sensitivity. These results suggest that a prospective study of MDM2 as a predictive biomarker in DDLPS is warranted.

IMPLICATIONS FOR PRACTICE

No validated biomarkers exist for treatment selection in dedifferentiated liposarcoma (DDLPS). Although murine double minute 2 (MDM2) is currently used for diagnosis, the clinical relevance of MDM2 amplification has yet to be fully assessed. This study found that MDM2 amplification follows a predictable distribution in DDLPS and correlates with clinical and biological outcomes. These data suggests that MDM2 amplification may be a useful biomarker in DDLPS.

Histological and molecular characterization of intrahepatic bile duct cancers suggests an expanded definition of perihilar cholangiocarcinoma

BACKGROUND

Growing evidence has suggested that intrahepatic cholangiocarcinoma (iCCA) can be classified into small- and large-duct types. The present study aimed to elucidate how large-duct iCCA is similar and dissimilar to perihilar cholangiocarcinoma (pCCA).

METHODS

The study cohort consisted of iCCA (n = 58) and pCCA (n = 44). After iCCA tumors were separated into small- (n = 36) and large-duct (n = 22) types based on our histologic criteria, genetic statuses of the three types of neoplasms were compared. Locations of iCCA were plotted on a three-dimensional image and their distances from the portal bifurcation were measured.

RESULTS

Large-duct iCCA was distinct from small-duct iCCA in terms of frequency of bile duct reconstruction required, perineural infiltration, and survival, with these features more similar to pCCA. Large-duct iCCA and pCCA more frequently had the loss of SMAD4 expression and MDM2 amplifications than small-duct iCCA, whereas the loss of BAP1 expression and IDH1 mutations were mostly restricted to small-duct iCCA. From imaging analysis, most tumors of large-duct iCCA were present around the second branches of the portal vein.

CONCLUSION

Large-duct type iCCA shared the molecular features with pCCA, and it may be reasonable to expand the definition of pCCA to include cancers originating from the second bile duct branches.