Complete remission with olaparib in BRIP1-mutated metastatic high-grade pleomorphic sarcoma: case study and literature review – an example of a genomic profiling-based tumor treatment, in a cancer type with high unmet clinical need

P3-09-05: Clinical outcome of patients with advanced triple negative breast cancer with germline and somatic variants in homologous recombination gene

Homologous recombination (HR) is a highly conserved DNA repair mechanism that protects cells from exogenous and endogenous DNA damage. Breast cancer 1 (BRCA1) and breast cancer 2 (BRCA2) play an important role in the HR repair pathway by interacting with other DNA repair proteins such as Fanconi anemia (FA) proteins, ATM, RAD51, PALB2, MRE11A, RAD50, and NBN. These pathways are frequently aberrant in cancer, leading to the accumulation of DNA damage and genomic instability known as homologous recombination deficiency (HRD). HRD can be caused by chromosomal and subchromosomal aberrations, as well as by epigenetic inactivation of tumor suppressor gene promoters. Deficiency in one or more HR genes increases the risk of many malignancies. Another conserved mechanism involved in the repair of DNA single-strand breaks (SSBs) is base excision repair, in which poly (ADP-ribose) polymerase (PARP) enzymes play an important role. PARP inhibitors (PARPIs) convert SSBs to more cytotoxic double-strand breaks, which are repaired in HR-proficient cells, but remain unrepaired in HRD. The blockade of both HR and base excision repair pathways is the basis of PARPI therapy. The use of PARPIs can be expanded to sporadic cancers displaying the “BRCAness” phenotype. Although PARPIs are effective in many cancers, their efficacy is limited by the development of resistance. In this review, we summarize the prevalence of HRD due to mutation, loss of heterozygosity, and promoter hypermethylation of 35 DNA repair genes in ovarian, breast, colorectal, pancreatic, non-small cell lung cancer, and prostate cancer. The underlying mechanisms and strategies to overcome PARPI resistance are also discussed.

Distinguishing dedifferentiated liposarcoma (DDLPS) from other high-grade spindle and pleomorphic sarcomas is important because of better prognosis in case of DDLPS. MDM2 amplification, a genetic abnormality of well-differentiated liposarcoma, is known to be present not only in DDLPS, but also in some other sarcomas. To differentiate DDLPS, we investigated MDM2 amplification and expression in high-grade spindle sarcomas. Eighty-five cases of nonlipogenic high-grade sarcomas, diagnosed between 2008 and 2011, were investigated. Tissue microarray, immunohistochemistry, and fluorescence in situ hybridization for MDM2 were performed. Forty-one of 85 cases (48.2%) showed MDM2 amplification and expression. Cases of MDM2 amplification were reclassified based on histology, immunophenotype, and clinical data. Thirty-nine of 41 cases, including those originally diagnosed as DDLPS (n=30), undifferentiated pleomorphic sarcoma (n=7), myxofibrosarcoma (n=1), and pleomorphic liposarcoma (n=1) could be reclassified as DDLPS. In addition, MDM2 immunohistochemistry and MDM2 fluorescence in situ hybridization showed an excellent correlation (P<0.001, sensitivity 92.7%, specificity 100%). MDM2 amplification and expression are potentially very useful in distinguishing between DDLPS and other undifferentiated high-grade spindle and pleomorphic sarcomas, even though a few other sarcomas also showed MDM2 amplification and expression.

Background: PARP inhibitors (PARPi) are FDA approved for a subset of metastatic human epidermal growth factor receptor 2-negative (H2N) breast cancer patients who harbor a germline pathogenic or likely pathogenic variant (PV) in BRCA1/2, two of the most well-described breast cancer susceptibility genes in the homologous recombination (HR) pathway. While the NCCN guidelines recommend consideration of BRCA1/2 testing for patients with H2N disease that are eligible for single-agent therapy, there are currently clinical trials available for women with advanced H2N breast cancer who have PVs in HR genes beyond BRCA1/2 to investigate outcomes of receiving PARPi. The yield of germline PVs in other HR genes in the H2N population is not well-described. Methods: Clinical histories and test results were reviewed for women with a diagnosis of H2N breast cancer who underwent multi-gene hereditary cancer panel testing that included a minimum of 10 homologous recombination (HR) genes in addition to BRCA1/2 (ATM, BARD1, BRIP1, CHEK2, FANCC, NBN, PALB2, PTEN, RAD51C, RAD51D). Those with prior BRCA1/2 testing were excluded. We assessed the yield of PVs in non-BRCA1/2 HR genes in the H2N breast cancer population. In addition, we compared the yield of PVs in non-BRCA1/2 HR genes in a “low risk” population (probands with H2N breast cancer with no reported personal history of ovarian or pancreatic cancer and no reported family history of breast, ovarian, pancreatic, or prostate cancer) to a “high risk” population (probands with H2N breast cancer who also have a personal history of ovarian or pancreatic cancer and/or a reported family history of breast, ovarian, pancreatic, or prostate cancer) via a two-tailed Fisher's exact test. Results: A total of 6179 women with H2N breast cancer were identified. Of these, BRCA1/2 PVs were identified in 4.8% (299/6179), while 5.7% (351/6179) carried PVs in HR genes other than BRCA1/2. These included CHEK2 (145), ATM (62), PALB2 (59), BRIP1 (26), FANCC (18), BARD1 (17), RAD51C (12), NBN (11), RAD51D (6), and PTEN (2). No statistically significant difference in the likelihood to harbor a PV in one of the 10 non-BRCA1/2 HR genes was observed between those with a “low risk” presentation (4.8% (53/1096) as compared to those with a “high risk” presentation (5.9% (298/5083)) (p=0.1956). Conclusions: Our findings show that the yield of PVs in HR genes other than BRCA1/2 is appreciable in the H2N breast cancer population. As such, it may be beneficial to include all HR genes when testing H2N breast cancer patients, regardless of other personal or family history, if and/or when a patient develops metastatic disease. Citation Format: Vogel Postula KJ, McGill AK, Sutcliffe E, Murphy PD, Klein RT, Hruska KS. Germline variants in non-BRCA homologous recombination genes detected in HER2-negative breast cancer patients [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-09-08.

Undifferentiated pleomorphic sarcomas (UPSs) are amongst the most common subtypes of soft-tissue sarcomas. Few real-world data on the use of immune checkpoint blockade (ICB) in UPS patients and other high-grade pleomorphic STS patients are available. The purpose of our study is to describe the efficacy and toxicity of ICB in patients with advanced UPSs and other high-grade pleomorphic sarcomas treated at our institution. This is a retrospective, observational study of all patients with metastatic high-grade pleomorphic sarcomas treated with FDA-approved ICB at MD Anderson Cancer Center between 1 January 2015 and 1 January 2023. Patients included in trials for which results are not yet published were excluded. Thirty-six patients with advanced/metastatic pleomorphic sarcomas were included. The median age was 52 years. A total of 26 patients (72%) had UPSs and 10 patients (28%) had other high-grade pleomorphic sarcomas. The median follow-up time was 8.8 months. The median PFS was 2.9 months. The 3-month PFS and 6-month PFS were 46% and 32%, respectively. The median OS was 12.9 months. The 12-month OS and 24-month OS were 53% and 29%, respectively. The best response, previous RT, and type of ICB treatment were significantly and independently associated with shorter PFS (p = 0.0012, p = 0.0019 and p = 0.036, respectively). No new safety signal was identified, and the toxicity was overall manageable with no toxic deaths and only four patients (11%) stopping treatment due to toxicity. Real-world retrospective data are consistent with the published literature, with a promising 6-month PFS of 32%. Partial or stable responders to ICB treatment have significantly improved PFS compared to progressors.

Pleomorphic sarcoma (PS) is a heterogeneous group of malignant mesenchymal tumors that lack specific histological differentiation. PS is characterized by genetic instability and diversity and unique histological features such as pronounced morphologic pleomorphism. PS is one of the most common soft tissue sarcomas. Complete surgical resection remains the only curative treatment and is often combined with neoadjuvant radiotherapy. Effective systemic chemotherapy is yet to be established, and PS frequently recurs locally and metastasizes to the lungs. Patient-derived cancer cell lines are invaluable tools for basic and preclinical research for developing novel chemotherapies. Herein, we report a high-grade pleomorphic spindle cell sarcoma, most consistent with myxofibrosarcoma cell line, NCC-PS2-C1, which was derived from a primary tumor specimen. NCC-PS2-C1 cells exhibited a range of copy number alterations. This cell line demonstrated consistent proliferation, spheroid formation, and invasive capabilities in vitro. Drug screening using NCC-PS2-C1 cells revealed that cobimetinib, crenolanib, and ixazomib were effective against PS. In conclusion, we established NCC-PS2-C1 cells from primary tumors of PS. This cell line is a valuable resource for developing novel chemotherapies.

Background: Breast cancer (BC) in men is a rare disease, but morbidity and mortality in male BC (MBC) patients is a serious concern. Because of its rarity, to date, clinical management of men with BC has been informed almost entirely by female BC research. However, BC in men and women may behave differently. Inherited mutations in homologous recombination (HR) genes, mainly BRCA1,BRCA2 and PALB2, play a major role in MBC predisposition. MBCs associated with mutations in HR gene are likely to represent a subgroup of tumors with a peculiar tumor phenotype. Here, we performed a transcriptome analysis of MBCs characterized for germline mutations in HR genes in order to provide insight into underlying HR pathways and characterize distinct molecular subtypes of MBC with possible clinical relevance. Materials and methods: MBC cases were selected to include cases with and without germline mutations in HR genes. Tumor samples with pathology and outcome data were selected within the Italian multicenter study on MBC that comprises 750 MBCs with information on germline mutations in 50 cancer-related genes. To enrich the series of MBC cases with germline mutations in HR genes, tumor samples from kConFab were also included. Overall, 63 tumor samples, including 26 cases with germline mutations in HR genes (BRCA2, BRCA1, PALB2, RAD50 and RAD51D) and 37 without germline mutations, were analyzed. Whole transcriptome data were obtained by RNA-sequencing using Illumina technology. A bioinformatic pipeline including FastQC tool for quality control, STAR for alignment, RSeQC-FPKM for counting reads, DESeq2 package for differential expression and DAVID for enrichment, was used. Tumor immunophenotype was evaluated using CIBERSORT, which accurately determines the fraction of 22 immune cell types. Statistical analyses were performed using Fisher exact test, t-test and log-rank test as appropriate. Results: A total of 724 differentially expressed genes, of which 355 up-regulated and 369 down-regulated, emerged between MBC cases with and without germline mutations in HR genes. Pathway-based analyses revealed different transcriptome profiles for genes involved in key biological processes, including translational initiation, cell cycle, DNA damage and repair. A higher fraction of activated CD4 memory T cells was observed in tumors with germline mutations in HR genes compared to those without mutations (p=0.04). Unsupervised clustering approach, based on the 2000 most variable transcripts among tumors, revealed two distinct subgroups with different biologic features and clinical outcome. In particular, tumors in subgroup 1 showed higher expression of genes involved in cell proliferation, were enriched for cases with germline mutations in HR genes (p=0.03), had lymph node involvement (p=0.04) and displayed a trend toward worse overall survival (p=0.09), when compared to tumors in subgroup 2. Conclusions: Integration of matched germline and tumor profiling seem to be a valuable approach for the identification of biologically and clinically relevant subtypes of MBC. Germline mutations in HR genes could impact on MBC transcriptome, defining molecular subgroups with peculiar biological features. Overall, these results may help to improve the clinical managements of MBC patients. Study supported by AIRC (IG 21389) to L.O. Citation Format: Veronica Zelli, Valentina Silvestri, Virginia Valentini, Agostino Bucalo, Piera Rizzolo, Ines Zanna, Laura Cortesi, Daniele Calistri, Maria Grazia Tibiletti, Giuseppe Giannini, Stephen B Fox, Domenico Palli, Laura Ottini. Matched germline and tumor profiling in male breast cancer for the discovery of molecular subtypes with clinical relevance [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-07-05.

BackgroundUndifferentiated high-grade pleomorphic sarcoma in gastrointestinal tract is extremely rare, and its prognosis is poor.Case presentationAn 82-year-old man visited a previous hospital complaining of fever, general fatigue, and shaking chill, for which he received antibiotics therapy. As the fever continued, he was referred to our hospital, where computed tomography and upper gastrointestinal endoscopy showed a 6-cm gastric tumor. A preoperative biopsy was consistent with a malignant mesenchymal tumor, but could not provide a definitive pathological diagnosis nor prove a cause-and-effect relationship between the chief complaint and the gastric tumor. The gastric tumor had grown to 8 cm in diameter within a month so we performed a partial gastrectomy. The pathological postoperative diagnosis was undifferentiated high-grade pleomorphic sarcoma that produced granulocyte colony-stimulating factor. The patient’s fever quickly improved, and he showed a good postoperative course.ConclusionsWe herein report a case of rapidly growing, undifferentiated, high-grade pleomorphic gastric sarcoma, which presented as a chief complaint of fever.

Sarcomas are rare forms of cancer with a high unmet clinical need that develop in connective tissue, such as muscle, bone, nerves, cartilage, and fat. The outcome for patients is poor, with surgery and postoperative radiotherapy the standard treatment for patients. A better understanding of the molecular pathology of sarcoma may allow for the development of novel therapeutics. There are dozens of sarcoma subtypes where there is a need for targetted therapeutics, with the most commonly studied including Ewing's sarcoma and osteosarcoma. Here we initiate a proteomics-based target-discovery program to define "dominant" pro-oncogenic signaling targets in the most common sarcoma in adults: high-grade pleiomorphic soft tissue sarcoma. We have carried out a proteome screen using tandem mass tag isobaric labeling on three high-grade undifferentiated pleomorphic sarcoma biopsies from different tissue sites. We identified the commonly dysregulated proteins within the three sarcomas and further validated the most penetrant receptor as CLIC1, using immunohistochemistry arising from two different population cohorts representing over 300 patients. The dominant expression of CLIC1 in a broad range of human sarcomas suggests that studying this relatively unexplored signaling pathway might provide new insights into disease mechanism and facilitate the development of new CLIC1 targeted therapeutics.

Background: Epithelial ovarian cancer (EOC) with homologous recombination (HR) deficiency is susceptible to PARP inhibitor therapy due to synthetic lethality. Identification of the patient population for PARP inhibitor therapy is imperative to reduce recurrence of EOC and improve the survival outcomes of patients. Current biomarkers for PARP inhibitor therapy consist of an array of genes involved in the HR repair pathway in EOC, including BRCA1, BRCA2 and PALB2. Through TCGA analysis, we found that the lysine (K)-specific methyltransferase 2C (KMT2C) gene is mutated in 10.3% of all EOC patients and considerably enriched in BRCA1 mutated EOC patients. However, the role of KMT2C in HR repair and PARP inhibitor sensitivity of EOC remains largely undefined. Methods: BRCA2-mutated PEO1 and BRCA2-wild type PEO1-NR cells were transfected with KMT2C siRNA and assayed for KMT2C protein expression by western blotting. DR-GFP (HR) and EJ5-GFP (NHEJ)-SKOV3 cell lines were co-transfected with the ISceI-expressing plasmid pCBA-ISceI and KMT2C siRNA. GFP-positive cells were analyzed by flow cytometry. SKOV3 cells were transfected with KMT2C siRNA and the expression of BRCA2 and Rad51 mRNA was determined using quantitative RT-PCR analysis. Results: siRNA-mediated knockdown of KMT2C resulted in marked down-regulation of KMT2C protein in PEO1 and PEO1-NR cells. KMT2C knockdown caused a significant decrease in ISceI-induced HR activity in DR-GFP-SKOV3 cells (p &amp;lt; 0.05). In contrast, KMT2C knockdown had no effects on ISceI-induced NHEJ activity in EJ5-GFP-SKOV3 cells. As a control, Rad51 knockdown caused complete suppression of HR activity and had no effects on NHEJ activity. Furthermore, quantitative RT-PCR analysis of key HR genes showed that KMT2C knockdown resulted in a moderate but significant down-regulation of BRCA2 (p &amp;lt; 0.05) and Rad51 (p &amp;lt; 0.01) expression in SKOV3 cells. Conclusion: Our results suggest that KMT2C partakes in the HR repair pathway in EOC. However, the contribution of KMT2C to HR activity is not rate-limiting. Based on the known function of KMT2C in histone modification, we speculate that KMT2C serves to positively regulate the transcription of HR genes and therefore promote HR activity. Future investigation into the exact roles of KMT2C in HR repair, etiology of EOC, and diagnostic biomarkers for the PARP inhibitor sensitivity of EOC is warranted. Citation Format: Mirielle C. Ma, Z. Ping Lin, Elena S. Ratner. The role of KMT2C in the homologous recombination repair in epithelial ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5606.

BACKGROUND: For many years malignant fibrous histiocytoma ("MFH") was accepted to be the most common soft tissue sarcoma in adults, its histiogenesis, however, remained controversial. METHODS: Review of the current status of "MFH". RESULTS: Within the last two decades several studies demonstrated that "MFH" has been used as a "waste paper basket" for several better classifiable, poorly differentiated soft tissue sarcomas. Therefore, reclassification of these tumors could led to better prognostification. CONCLUSIONS: In the 21st century with the insight of immunohistochemistry as well as improved cytogenetic and molecular diagnostic the term high-grade undifferentiated pleomorphic sarcoma (so-called "MFH") should be restricted to a group of soft tissue malignancies without a specific line of differentiation. Better classification of various high-grade sarcomas may contribute to more specific treatment options and hence lead to improved survival for patients.

Is it a prime time for germline genetic testing for HCC?

Background. Pleomorphic sarcoma is an aggressive soft tissue sarcoma. In patients with high-risk extremity sarcomas, the significant survival benefits conferred by an intense regimen of neoadjuvant chemoradiotherapy and surgery were reported. To our knowledge, this is the first report in the literature of the neoadjuvant use of trabectedin in a patient with high-grade pleomorphic sarcoma, ineligible for standard neoadjuvant combination therapy with an anthracycline-based regimen. Case Presentation. Here we present a 58-year-old White male with a large tumor in the left thigh, but with no signs of metastases. Owing to the history of severe heart attack, three cycles of neoadjuvant trabectedin were administrated to achieve surgically wide margins. After two cycles, an 18F-FDG-PET showed a large proportion of the central tumor area was without metabolic activity. According to RECIST and Choi criteria, the tumor was stable. After the third cycle of trabectedin, the patient underwent a complete resection, which revealed completely necrotic high-grade pleomorphic sarcoma (stage pT2b), with only a small vital area. Conclusion. The present paper on a promising treatment with neoadjuvant trabectedin of patients with high-grade pleomorphic sarcoma might suggest that such treatment approach may provide a greater chance of cure and survival of such patients.

As a drug class, inhibitors of poly-(ADP-ribose) polymerase (PARP) have had their greatest impact on the treatment of women with epithelial ovarian cancers (EOC), in particular, those with the most common histological subtype, high-grade serous cancer, as it has high rates of homologous recombination (HR) deficiency. PARP inhibition exploits this cancer vulnerability by further disrupting DNA repair, thus leading to genomic catastrophe. Early clinical data demonstrated the effectiveness of PARP inhibition in women with recurrent EOC harbouring BRCA1/2 mutations and those with platinum-sensitive recurrences. Three PARP inhibitors (olaparib, niraparib, and rucaparib) are now approved for use in women with recurrent EOC. Based upon randomised controlled trials, PARP inhibitors are in use as "maintenance" therapy for those with platinum-sensitive and platinum-responsive recurrences (irrespective of BRCA1/2 mutation status). Among women with BRCA1/2 mutations (either germline or somatic), maintenance PARP inhibitor therapy for those with recurrence has led to a nearly fourfold prolongation of progression-free survival compared to placebo control. Those without BRCA1/2 mutations experience an approximately twofold increase in progression-free survival. The latest clinical data demonstrate that women with BRCA1/2 mutations who respond to first-line chemotherapy and go on to have maintenance olaparib experience a doubling of the rate of freedom from death at 3years when compared to placebo (60% vs 27%). PARP inhibitors are also approved as active therapy for women with germline or tumour BRCA1/2 mutations and recurrent EOC treated with three or more prior lines of therapy. Apart from the presence of a BRCA1/2 mutation (germline or somatic) and clinical factors such as platinum sensitivity and responsiveness, other predictive biomarkers are not in routine clinical use. Assays to identify genomic aberrations caused by HR deficiency, or mutations in genes involved in HR, have not been sufficiently sensitive to identify all patients who benefit from treatment. The mechanisms of PARP-inhibitor resistance include restoration of HR through reversion mutations in HR genes, capable of re-establishing the DNA open-reading frame and leading to resumed HR function. Other mechanisms that sustain sufficient DNA repair may also be important. This review focuses on the rationale for the use of PARP inhibitors in EOC. The data that have shaped clinical research are presented, and the trials that have changed management standards are reviewed and discussed. Highlighted are the past and ongoing efforts to further improve and explore the use of PARP inhibitors in EOC.

Left Atrial High-Grade Undifferentiated Pleomorphic Sarcoma Protruding Through the Mitral Valve