Subcutaneous extraskeletal osteosarcoma of the foot: A case report

Extraskeletal osteosarcoma (ESOS) is a rare variant of osteosarcoma which occurs exclusively in the soft tissue without any bone involvement. Subcutaneous ESOS, in particular, is very rare and is seen in <10% of cases. Here, we report a case of a subcutaneous tumor in the fourth web space of the left foot in a 73-year-old man. The diagnosis of ESOS was made on histology and by immunohistochemical reactivity to special AT-rich sequence-binding protein 2 (SATB2), which is a sensitive, nuclear marker of osteoblastic differentiation. We present this case because of its rarity and the use of SATB2 immunohistochemistry to confirm the diagnosis.

circABCB10 Promotes Malignant Progression of Gastric Cancer Cells by Preventing the Degradation of MYC

Objective. To investigate the role of circABCB10 in gastric cancer and the molecular mechanism of promoting malignant progression of gastric cancer cells by preventing the degradation of MYC by hsa-miR-1252-5p. Methods. The expression of circABCB10 in gastric cancer tissues and cells was detected by real-time quantitative PCR. MTT, Transwell, clone formation, and TUNEL assay were used to detect the effects of circABCB10 on the proliferation, invasion, and apoptosis of gastric cancer cells. A subcutaneous tumor-bearing model was established to study the inhibitory effect of knockdown circABCB10 on gastric cancer proliferation. The dual luciferase reporter gene assay and RNA pull-down assay were used to verify the regulatory effect of circABCB10 on miR-1252-5p and the regulatory effect of miR-1252-5p on MYC. Results. Compared with paracancerous tissues and gastric mucosal epithelial cells, the expression of circABCB10 was significantly increased in human gastric cancer tissues and gastric cancer cells. circABCB10 knockout significantly decreased cell viability and invasion ability and promoted cell apoptosis ( P < 0.01 ). Subcutaneous tumor-bearing experiments in nude mice demonstrated that circABCB10 knockdown inhibited the proliferation of gastric cancer cells. circABCB10 can act as a sponge for miR-1252-5p in gastric cancer cells. Meanwhile, MYC is the target gene of miR-1252-5p. Overexpression of miR-1252-5p and knockdown of MYC reversed the promoting effect of circABCB10 on gastric cancer. Conclusion. circABCB10 can promote the proliferation, invasion, and clonal formation of gastric cancer cells by targeting miR-1252-5p and upregulating the expression of MYC. circABCB10/miR-1252-5p/MYC constitutes the regulatory mechanism of ceRNA.

DDRE-01. CDK PATHWAY INHIBITION WITH ABEMACICLIB IMPROVES INTRACRANIAL AND EXTRACRANIAL RESPONSE TO CHECKPOINT BLOCKADE IN PRE-CLINICAL MODELS OF MELANOMA BRAIN METASTASIS

While immune checkpoint inhibitors (ICI) have revolutionized treatment of metastatic melanoma, few of the 75% of patients who develop brain metastases benefit from immunotherapy. Inhibition of CDK4/6 pathway – altered in ~90% of melanoma patients – can reportedly increase tumor inflammation and sensitize extracranial tumors to ICI. To determine whether intracranial melanoma can be similarly sensitized, we studied efficacy of combination CDK4/6 inhibitor Abemaciclib and ICI in immunocompetent mouse models of melanoma brain metastases bearing concurrent intracranial and extracranial tumors. 8-week-old female C57BL/6 mice received subcutaneous injections of 2x105 YUMM1.7 or B16-F10 melanoma cells 3 days prior to intracranial injections of 5x104 YUMM1.7 cells or 5x103 B16-F10 cells respectively. Mice were randomized into 6 treatment groups (n=5-7/group): Abemaciclib alone, anti-PD-1 monotherapy, anti-PD-1 and anti-CTLA4 combined (combination ICI), Abemaciclib and anti-PD-1, Abemaciclib combined with anti-PD-1 and anti-CTLA4 (triple therapy), and treatment with vehicle and isotype-matched antibodies as control. In mice bearing YUMM1.7 tumors, subcutaneous tumor growth was significantly reduced compared to control in mice treated with Abemaciclib alone (p&lt; 0.05), combination ICI (p&lt; 0.05) and triple therapy (p&lt; 0.05). However, improvement in survival was only observed with triple therapy (p=0.039) compared to control group. In mice bearing B16-F10 tumors, we observed striking reduction in subcutaneous tumor growth in mice treated with Abemaciclib and anti-PD-1 compared to control-treated mice (p=0.0016) or to mice receiving anti-PD-1 monotherapy (p=0.000056). This further corresponded to a significant increase in survival of Abemaciclib and anti-PD-1 treated mice compared to control (p=0.02). Additionally, we observed improved survival in mice treated with combination ICI (p=0.006) or triple therapy (p=0.01). These results indicate CDK4/6 inhibition with Abemaciclib can improve both extracranial and intracranial responses to ICI and sensitize melanoma brain metastases to immunotherapy. Our pre-clinical findings warrant further investigation to determine whether this combination approach can improve patient outcomes.

Two-pronged anti-tumor therapy by a new polymer-paclitaxel conjugate micelle with an anti-multidrug resistance effect

Cancerous tumors are still a major disease that threatens human life, with tumor multidrug resistance (MDR) being one of the main reasons for the failure of chemotherapy. Here, a reduction-sensitive polymer prodrug micelle, mPEG-DCA-SS-PTX (PDSP), was manufactured with a new polymer inhibitor of drug-resistance as a carrier to overcome MDR and improve the anti-tumor effect of paclitaxel (PTX). The PDSP micelles display good stability, double-responsive drug release, and excellent biocompatibility. The PDSP micelles reduced the cytotoxicity of PTX to normal HL-7702 cells, and enhanced that to SMMC-7721 and MCF-7 cells in vitro. Improved sensitivity of A549/ADR to PDSP was also observed in vitro. Furthermore, in vivo experiments show reduced systemic toxicity and enhanced therapeutic efficacy of DOX to H22 subcutaneous tumor-bearing mice. This work proves the reduction sensitive polymer prodrug micelles carried by the new polymer inhibitor can be used as an alternative delivery system to target tumors and reverse MDR for paclitaxel and other tumor-resistant drugs.

Oxaliplatin Compromised CDK1 Activity Sensitizes BRCA-Proficient Cancers to PARP Inhibition in Oxaliplatin Resistance Gastric Cancer

Background: Oxaliplatin resistance is one of the most important problems in the treatment of cancer. The successful culture of tumor organoid in gastric cancer can help us to study oxaliplatin resistance and its mechanism. Thus, it is convenient for us to successfully solve oxaliplatin resistance and improve the prognosis of patients.Methods: Two oxaliplatin resistant patients and two oxaliplatin sensitive patients were enrolled through our Gastric Cancer Center of Sun Yat-sen University. Core genes of oxaliplatin resistant and non-resistant patients were analyzed by sequencing. The overexpression and knockdown of core genes were carried out by organoid in vivo, combined with oxaliplatin-resistant cell lines AGS, MKN74 and SNU719 for cell viability, WB and immunofluorescence, etc., to verify the role of core genes in oxaliplatin resistance. Again, in vivo experiments were verified by subcutaneous tumor formation in vitro.Results: Through sequencing, we found that PARP1 is an important core gene leading to oxaliplatin resistance. In vivo organoids, oxaliplatin resistant cell lines and subcutaneous tumor formation in vivo. We found that PARP1 was an important cause of oxaliplatin resistance. Oxaliplatin can inhibit CDK1 activity and make cancer with normal BRCA1 function sensitive to PARP inhibition. Through the combination of oxaliplatin and PARP1 inhibitor olaparib, we can effectively kill tumor cells. Through the patients' follow-up data, we found that the expression level of PARP1 was significantly correlated with oxaliplatin resistance.Conclusion: Our results indicate that PARP1 is an important core gene leading to oxaliplatin resistance. Combined oxaliplatin and PARP1 inhibitor olaparib can effectively kill tumor cells. Oxaliplatin can inhibit CDK1 activity and make cancers with normal BRCA1 function more sensitive to PARP inhibitors.