Granberg, Candace F.

Abstract Introduction: Pediatric rhabdomyosarcoma (RMS) is the most common soft tissue tumor in children, with nearly 20% of children presenting with locally aggressive and/or metastatic disease. Despite aggressive chemotherapy and radiotherapy, the 5-year overall survival rate is still less than 40%. In addition, resistance to chemotherapy remains the major cause of cancer-related mortality. Therefore, there is an unmet need to develop more effective and tolerable therapeutic strategies for the treatment of RMS. Our overall objective is to leverage transcriptomic and proteomic profiling methods to identify RMS-specific surface proteins targetable with immune-based therapies. Methods: To identify therapeutic targets, we performed cell-surface capture and mass spectrometry on fusion-positive (FP), fusion-negative (FN) RMS and normal skeletal muscle. Transcriptomic datasets of RMS tumor specimens and normal tissue were employed to identify high-confidence RMS-specific cell-surface proteins. Expression of immune checkpoint molecules was confirmed by flow cytometry, western blot and PCR. Paraffin-embedded tissue sections were used to determine protein expression and prognostic value in RMS patients. We developed an in vitro T-cell killing assay to assess the functional role of immune checkpoint molecules on the antitumor immune response. Results: Surfaceome profiling of RMS cells revealed unique protein signatures specific for each tumor type and normal tissue. We have identified 5061 cell-surface proteins in RMS and 31.6% of proteins were correctly located at the plasma membrane. By integrating proteomic and transcriptomic data, we have identified 30 and 38 proteins significantly overexpressed in fusion-negative and fusion-positive RMS respectively compared to normal muscle. We have identified the immune checkpoint molecule B7-H3 as cell-surface protein overexpressed in both RMS subtypes. Strong expression of B7-H3 was also observed in patient’s tumor specimens. Genetic deletion of B7-H3 gene in RMS cells was associated with higher antitumor immune response in tumor cells co-cultured with CD8+-T cells. No difference was observed in tumor cell proliferation and radioresistance. Conclusions: Through integrated transcriptomic and proteomic profiling, we have discovered B7-H3 as a key regulator of tumor immune-evasion in RMS. B7-H3 is a suitable immunotherapy target for the treatment of RMS. Further studies are warranted to elucidate underlying mechanisms of B7-H3 function in RMS. Citation Format: Roxane R. Lavoie, Fabrice Lucien, Patricio C. Gargollo, Mohamed E. Ahmed, Yohan Kim, Emily Baer, Doris Phelps, Cristine M. Charlesworth, Benjamin J. Madden, Liguo Wang, Peter J. Hougthon, John Cheville, Haidong Dong, Candace F. Granberg. Surfaceome profiling of rhabdomyosarcoma reveals B7-H3 as a mediator of immune evasion [abstract]. In: Proceedings of the AACR Special Conference: Sarcomas; 2022 May 9-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(18_Suppl):Abstract nr A036.

Novel therapeutic strategies are needed for the treatment of rhabdomyosarcoma (RMS), the most common soft-tissue sarcoma in children. By using a combination of cell surface proteomics and transcriptomic profiling of RMS and normal muscle, we generated a catalog of targetable cell surface proteins enriched in RMS tumors. Among the top candidates, we identified B7-H3 as the major immunoregulatory molecule expressed by RMS tumors. By using a large cohort of tissue specimens, we demonstrated that B7-H3 is expressed in a majority of RMS tumors while not detected in normal human tissues. Through a deconvolution analysis of the RMS tumor RNA-seq data, we showed that B7-H3-rich tumors are enriched in macrophages M1, NK cells, and depleted in CD8+-T cells. Furthermore, in vitro functional assays showed that B7-H3 knockout in RMS tumor cells increases T-cell mediated cytotoxicity. Altogether, our study uncovers new potential targets for the treatment of RMS and provides the first biological insights into the role of B7-H3 in RMS biology, paving the way for the development of next-generation immunotherapies.

Abstract Introduction: Pediatric rhabdomyosarcoma (RMS) is the most common soft tissue tumor in children, with nearly 20% of children presenting with locally aggressive and/or metastatic disease. Despite aggressive chemotherapy and radiotherapy, the 5-year overall survival rate is still less than 40%. In addition, resistance to chemotherapy remains the major cause of cancer-related mortality. Therefore, there is an unmet need to develop more effective and tolerable therapeutic strategies for the treatment of RMS. Our overall objective is to leverage transcriptomic and proteomic profiling methods to identify RMS-specific surface proteins targetable with immune-based therapies. Methods: To identify therapeutic targets, we performed cell-surface capture and mass spectrometry on fusion-positive (FP), fusion-negative (FN) RMS and normal skeletal muscle. Transcriptomic datasets of RMS tumor specimens and normal tissue were employed to identify high-confidence RMS-specific cell-surface proteins. Expression of immune checkpoint molecules was confirmed by flow cytometry, western blot and PCR. Paraffin-embedded tissue sections were used to determine protein expression and prognostic value in RMS patients. We developed an in vitro T-cell killing assay to assess the functional role of immune checkpoint molecules on the antitumor immune response. Results: Surfaceome profiling of RMS cells revealed unique protein signatures specific for each tumor type and normal tissue. We have identified 5061 cell-surface proteins in RMS and 31.6% of proteins were correctly located at the plasma membrane. By integrating proteomic and transcriptomic data, we have identified 30 and 38 proteins significantly overexpressed in fusion-negative and fusion-positive RMS respectively compared to normal muscle. We have identified the immune checkpoint molecule B7-H3 as cell-surface protein overexpressed in both RMS subtypes. Strong expression of B7-H3 was also observed in patient's tumor specimens. Genetic deletion of B7-H3 gene in RMS cells was associated with higher antitumor immune response in tumor cells co-cultured with CD8+-T cells. No difference was observed in tumor cell proliferation and radioresistance. Conclusion: Through integrated transcriptomic and proteomic profiling, we have discovered B7-H3 as a key regulator of tumor immune-evasion in RMS. B7-H3 is a suitable immunotherapy target for the treatment of RMS. Further studies are warranted to elucidate underlying mechanisms of B7-H3 function in RMS. Citation Format: Roxane R. Lavoie, Yohan Kim, Mohamed E. Ahmed, Doris Phelps, Emily Baer, Cristine Charlesworth, Benjamin Madden, Liguo Wang, Haidong Dong, Peter Houghton, John Cheville, Patricio Gargollo, Candace Granberg, Fabrice Lucien. Surfaceome profiling identifies the immune checkpoint molecule B7-H3 as a key player of immune-evasion in rhabdomyosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3048.

SAGE-Journals-Accessible-Video-Player 10.1089/vid.2020.0112.M1 sj-vid-1-vid-10.1089_vid.2020.0112

Background Most children with intermediate‐risk rhabdomyosarcoma (RMS) have gross disease (group III) at the initiation of chemotherapy. Delayed primary excision (DPE) after induction chemotherapy allows for a reduction in adjuvant radiation dose, but with the risk of potential surgical morbidity. The objectives of this study were to compare outcomes in children with group III RMS who did and did not undergo DPE and to assess surgical morbidity. Methods The study included 369 patients who had clinical group III RMS at sites amenable to DPE from intermediate‐risk Children's Oncology Group studies D9803 (encouraged DPE) and ARST0531 (discouraged DPE). Results The primary tumor site was bladder/prostate (136 patients; 37%), extremity (97 patients; 26%), trunk (24 patients; 7%), retroperitoneum (91 patients; 25%), or intrathoracic/perineum/perianal (21 patients; 6%). In total, 112 patients (53.9%) underwent DPE in D9803, and 26 patients (16.2%) underwent DPE in ARST0531 ( P < .001), with loss of vital organ or function in 30 of 138 patients (22%). DPE allowed for a reduced radiation dose in 110 of 135 patients (81%; 51% were reduced to 36 Gy, and 30% were reduced to 42 Gy). Patients who underwent DPE had improved unadjusted overall survival ( P = .013). In adjusted regression analysis, the risk of death (hazard ratio, 0.71; 95% CI 0.43‐1.16) was similar for patients who did and did not undergo DPE and was improved for the subset of patients who had tumors of the trunk and retroperitoneum (hazard ratio, 0.44; 95% CI, 0.20‐0.97). Conclusions Children with group III RMS have equivalent or improved outcomes with DPE and can receive a decreased radiation dose for definitive local control. The choice of local control modality should weigh the potential morbidity of surgery versus that of higher dose irradiation.

AbstractBackgroundThe use of spinal anesthesia in infants is seeing resurgence as an alternative to general anesthesia.AimsOur primary aims are to describe our institution's experience introducing a spinal anesthesia and sedation protocol for infants undergoing urologic surgery, to describe methods of improving prolonged anesthesia, and to describe the failure rate of spinal anesthesia in these patients. Sedation was provided for some infants with intranasal dexmedetomidine ± fentanyl.MethodsThis is a retrospective case series examining infants aged 1‐<14 months who received spinal anesthesia for circumcision, orchiopexy, orchiectomy, hypospadias repair, or epispadias repair. The electronic medical record was reviewed and compared with unmatched historical controls who received general anesthesia.ResultsA total of 230 patients underwent a urologic procedure; 102 patients received spinal anesthesia and 128 received general anesthesia. Length of surgical time with spinal anesthesia ranged from 4 to 189 minutes. The hospital length of stay was shorter in the spinal anesthesia group (median [IQR] of 5.3 hours [4.3, 7.2]) compared to the general anesthesia group (17.1 hours [15.6, 17.5]).The median bupivacaine dose was 0.75 mg/kg [0.67, 0.85]. There was one case in which cerebral spinal fluid was unable to be obtained, and one case that required conversion to general anesthesia after surgery had started. There were no cases of apnea, bleeding, infection, or neurologic compromise.ConclusionsWe describe the successful implementation of an infant spinal anesthesia and sedation protocol and a technique that uniquely provides prolonged surgical anesthesia with a low failure rate. We also report shorter anesthesia time, surgical time, and recovery room length of stay in patients who received spinal anesthesia compared to general anesthesia.