MAP2K1 Mutations Research Articles

Evaluation of Heterogeneity in the Coding Region of BRAF, MAP2K1, and MAP2K2 Genes in Primary and Metastatic Melanomas.

The incidence of melanoma has been increasing in recent decades. BRAF mutations appear in 50%-70% of melanomas. The BRAF-targeted therapy increased the disease-free survival of patients with metastatic melanoma, but this response may be short, due to several resistance mechanisms, such as the presence of other subclones with mutations. Evaluation of mutations and heterogeneity in the coding region of the BRAF, MAP2K1, and MAP2K2 genes in primary and metastatic melanomas. Twenty-seven samples of primary and metastatic superficial spreading melanoma (SSM) and acral lentiginous melanoma (ALM) were analyzed for BRAF, MAP2K1, and MAP2K2 mutations using the next-generation sequencing technique. In ALM, the mutation rate found was 50% in the BRAF and MAP2K1 genes and 28.6% in MAP2K2. In the SSM, BRAF was mutated in 76.9%, MAP2K1 in 30.8%, and MAP2K2 in 23.2% of the cases. All samples were formed by distinct tumor subclones in the same lesion. Intertumoral heterogeneity was present between primary and metastatic lesions of ALM in BRAF, MAP2K1, and MAP2K2; the cases of SSM were heterogeneous for BRAF and MAP2K1. We sought to evaluate the mutations in the BRAF, MAP2K1, and MAP2K2 genes, revealing a heterogeneous mutation profile in samples of ALM and SSM.

MAP3K1 mutations confer tumor immune heterogeneity in hormone receptor-positive HER2-negative breast cancer.

Hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancer, the most common type of breast cancer, is facing challenges such as endocrine therapy resistance and distant relapse. Immunotherapy has shown progress in treating triple-negative breast cancer, but immunological research on HR+/HER2- breast cancer is still in its early stages. Here, we performed a multi-omics analysis of a large cohort of HR+/HER2- breast cancer patients (n = 351) and revealed that HR+/HER2- breast cancer possessed a highly heterogeneous tumor immune microenvironment. Notably, the immunological heterogeneity of HR+/HER2- breast cancer was related to MAP3K1 mutation and we validated experimentally that MAP3K1 mutation could attenuate CD8+ T cell-mediated antitumor immunity. Mechanistically, MAP3K1 mutation suppressed MHC-I-mediated tumor antigen presentation through promoting the degradation of antigen peptide transporter 1/2 (TAP1/2) mRNAs, thereby driving tumor immune escape. In preclinical models, the postbiotics tyramine could reverse the MAP3K1 mutation-induced MHC-I reduction, thereby augmenting the efficacy of immunotherapy. Collectively, our study identified the vital biomarker driving the immunological heterogeneity of HR+/HER2- breast cancer and elucidated the underlying molecular mechanisms, which provided the promise of tyramine as a novel therapeutic strategy to enhance the efficacy of immunotherapy.

Role of Targeted Sequencing in Routine Diagnostics of Spitz Melanocytic Neoplasms-An Analysis of 70 Cases.

There is growing evidence that the Spitz group of melanocytic neoplasms should be restricted to those harboring kinase receptor fusions and HRAS mutations/11p15 amplification. The presence of genomic alterations characteristic of conventional melanomas (BRAF and NRAS mutations) precludes a diagnosis of a Spitz neoplasm. It is often challenging to distinguish Spitz neoplasms from conventional melanomas with spitzoid morphology on histopathological grounds alone. We report a series of 70 consecutive melanocytic tumors in which targeted sequencing was indicated to distinguish Spitz from spitzoid neoplasms and to classify Spitz neoplasms along the biological spectrum. Final diagnoses incorporating molecular results included 12 conventional melanomas (nine of which with NRAS mutations), five Spitz melanomas, 35 atypical Spitz tumors, eight Spitz nevi, three melanocytic tumors with a MAP2K1 mutation, and seven desmoplastic Spitz nevi/tumors. There were significant discrepancies between initial diagnoses and final diagnoses after incorporating molecular results in 24 (34%) cases, including nine conventional melanomas favored to be Spitz neoplasms and nine Spitz neoplasms favored to be conventional melanomas. It is often not possible to reliably distinguish Spitz neoplasms from spitzoid melanocytic tumors without identifying their driver genomic alterations. Applying next-generation sequencing in diagnostically problematic tumors improves diagnostic accuracy.

Intramuscular hemangioma capillary type with HRAS mutation: Expanding the molecular genetic spectrum with an emphasis on overlap with arteriovenous malformations and distinct from infantile hemangioma

AimsIntramuscular hemangioma capillary type (IHCT) is a rare entity that refers to fast-flow vascular lesions. This study aims to elucidate the relationships between clinicopathological, radiological, and molecular characteristics in IHCT patients. Methods and resultsWe reviewed all IHCT cases which were treated surgically in our pathology database from 2014 to 2023. Ten cases were analyzed via next-generation sequencing (NGS) and Sanger sequencing. The cohort consisted of 10 patients (6 males, 4 females) with a median age of 18 years (range: 1–37). Disease lesions were located in the trunk (n = 4), upper extremity (n = 2), lower extremity (n = 2), shoulder (n = 1), and neck (n = 1). IHCT is most commonly a progressively increasing painless mass. Histopathologically, all lesions exhibited aggregates, lobules, and anastomosing cords of capillary-type vessels separating or infiltrating the skeletal muscles. Four cases exhibited irregularly dilated vessels with thick walls, such as arteriovenous malformations (AVM) in the lesion's periphery. MRI findings commonly demonstrated a well-delineated, homogeneous mass. Somatic mutations were detected in seven of the ten IHCT cases. Four cases harbored mutations in MAP2K1 (p.Q58_E62del, p.K57_G61del, p.K57 N), two cases harbored mutations in KRAS (p.Q61R and p.L56V, p.G13R), and one case harbored a mutation in HRAS (p.D69_Q70insRWYSAMRD). Mutant allele frequencies detected by sequencing ranged from 9.98% to 15.97%. ConclusionsThe hemodynamic and molecular genetic phenotypes of IHCT closely resemble those observed in AVMs. Newly identified KRAS missense mutations, including cases with coexisting mutation types, and HRAS insertion mutations offer valuable insights into the genetic basis of vascular anomalies. These findings may also present potential targets for the development of novel pharmacotherapeutic interventions.

7292 Central AVP Deficiency in Erdheim-Chester Disease in the Era of Molecular Diagnostics

Abstract Disclosure: J. Hewlett: None. S. Mohan: None. C.J. Davidge-Pitts: None. J. Abeykoon: None. R. Go: None. D.Z. Erickson: None. Objective: Erdheim-Chester Disease (ECD) is a multisystem histiocytic disorder which can infiltrate the pituitary gland, often leading to endocrine dysfunction. Central Arginine Vasopressin Deficiency (cAVP-D) commonly affects ECD patients, and those harboring BRAFV600E are reported to have an increased risk. Insufficient data exist about the risk associated with other mutations, and if cAVP-D or pituitary imaging improves with targeted therapies (TT). Methods: We conducted a review of a prospectively maintained database of adults with ECD treated at a tertiary center between 1992-2023. Objectives of this study were to identify mutations associated with cAVP-D and assess for improvement in cAVP-D (remission of disease or decrease in dose of desmopressin) or pituitary gland involvement (via MRI imaging) following TT for ECD. Results: Of 148 patients with ECD, the majority were male (98, 66.2%) and the mean age at diagnosis was 56.5 years [range: 19-82]. Median length of follow-up was 24 months (95% CI, 17 to 27). Of 121 (81.8%) patients with molecular testing results, 89 (73.6%) harbored a somatic mutation. 67 of 89 (75.3%) carried BRAF mutations, with BRAFV600E in 61 (91.0%) and missense mutations/fusions in 6 (9.0%). 22 of 89 (24.7%) patients harbored other somatic mutations, with MAP2K1 in 13 (14.6%) being the most common. 35 (23.6%) patients were diagnosed with cAVP-D, and the median onset of polyuria and polydipsia prior to diagnosis of ECD was 51 months (95% CI, -120 to -6). Molecular testing was performed in 28 patients with cAVP-D: 17 (60.7%) harbored BRAF mutation and 3 (10.7%) MAP2K1 mutation. There was no significant association between the presence of cAVP-D and MAP2K1 (p=0.69, 95% CI, -0.08 to 0.21). The association between cAVP-D and BRAF did not reach statistical significance (p=0.07, 95%CI, -0.03 to 0.38). Additionally, there was no association between BRAF and timing of cAVP-D symptoms before ECD diagnosis (p=0.08, 95% CI -163.4 to 10.3). Pituitary MRI was available in 32 patients with cAVP-D (91.4%) showing infundibular involvement in 17 (53.1%) and loss of the posterior bright spot in 5 (15.6%). 28 (80%) patients with cAVP-D received systemic therapy, 18 (64.3%) of whom received TT. One patient with cAVP-D was able to discontinue desmopressin. Improvement of pituitary MRI was noted in 7 (21.9%), among whom 4 received TT, 2 received systemic non-TT, and 1 was lost to follow-up. There was no significant MRI improvement associated with TT (p=0.67, 95% CI -0.30 to 0.42). Conclusion: In this large cohort of patients with ECD, of whom the majority underwent molecular testing, we identified no association between MAP2K1 mutation and cAVP-D, and no impact of TT on the clinical course or MRI findings associated with cAVP-D. BRAF mutation carriers were more likely to have cAVP-D and more likely to have onset of symptoms closer to ECD diagnosis, but the results did not reach statistical significance. Presentation: 6/2/2024

Rosai-Dorfman-Destombes disease in adults: a single center experience.

Recent advances in Rosai-Dorfman-Destombes disease (RDD), notably molecular testing, targeted therapy, and PET-CT imaging, hold promise for better recognition and improved outcomes. This study presents patients diagnosed and treated in a "real world" setting, where navigating limited resources must be considered. This retrospective single-center review includes 15 adult patients diagnosed with RDD at Vancouver General Hospital between November 2015 and October 2023. The cohort comprised five males and ten females with a median age 53years (range 19-80years). All 15 patients had extra-nodal disease; 11 patients exclusively had extra-nodal disease, and four patients also had lymph node involvement. Seven patients had tissue next-generation sequencing, identifying MAP2K1 mutations in four cases and a KRAS p.K117N mutation in one case that was treated with targeted therapy using trametinib. PET-CT was used for disease staging in four cases. Six patients with refractory disease tolerated lenalidomide and dexamethasone without significant toxicity; three patients achieved complete response, and three had partial response. This study highlights RDD's diverse extra-nodal manifestations. Lenalidomide combined with dexamethasone is an effective and well-tolerated treatment option for select patients, especially those with refractory disease. Broad utilization of NGS and PET-CT can positively influence management decisions.

A disease-associated PPP2R3C-MAP3K1 phospho-regulatory module controls centrosome function

Centrosomes have critical roles in microtubule organization, ciliogenesis, and cell signaling.1,2,3,4,5,6,7,8 Centrosomal alterations also contribute to diseases, including microcephaly, cancer, and ciliopathies.9,10,11,12,13 To date, over 150 centrosomal proteins have been identified, including several kinases and phosphatases that control centrosome biogenesis, function, and maintenance.2,3,4,5,14,15,16,17,18,19,20,21 However, the regulatory mechanisms that govern centrosome function are not fully defined, and thus how defects in centrosomal regulation contribute to disease is incompletely understood. Using a systems genetics approach, we find here that PPP2R3C, a poorly characterized PP2A phosphatase subunit, is a distal centriole protein and functional partner of centriolar proteins CEP350 and FOP. We further show that a key function of PPP2R3C is to counteract the kinase activity of MAP3K1. In support of this model, MAP3K1 knockout suppresses growth defects caused by PPP2R3C inactivation, and MAP3K1 and PPP2R3C have opposing effects on basal and microtubule stress-induced JNK signaling. Illustrating the importance of balanced MAP3K1 and PPP2R3C activities, acute overexpression of MAP3K1 severely inhibits centrosome function and triggers rapid centriole disintegration. Additionally, inactivating PPP2R3C mutations and activating MAP3K1 mutations both cause congenital syndromes characterized by gonadal dysgenesis.22,23,24,25,26,27,28 As a syndromic PPP2R3C variant is defective in centriolar localization and binding to centriolar protein FOP, we propose that imbalanced activity of this centrosomal kinase-phosphatase pair is the shared cause of these disorders. Thus, our findings reveal a new centrosomal phospho-regulatory module, shed light on disorders of gonadal development, and illustrate the power of systems genetics to identify previously unrecognized gene functions.

Trametinib for a child with refractory Rosai-Dorfman-Destombes disease harboring a novel somatic mutation in MAP2K1.

Rosai-Dorfman-Destombes disease (RDD) is a rare histiocytosis characterized by accumulation of S100 + , CD68 + , and CD1a- histiocytes, with emperipolesis. It occurs predominantly in black adolescents and young adults, but rarely in Japanese children. Recently, oncogenic mutations in mitogen-activated protein kinase (MAPK) pathway genes were reported in 30-50% of patients with RDD, and several studies have described treatment of adult patients with MAPK inhibitors. Here, we present the case of a Japanese boy with refractory RDD without signs of cardiofaciocutaneous (CFC) syndrome who harbored MAP2K1 p.Lys59del and responded to trametinib. The patient had lymph node, nasal cavity, kidney, upper respiratory tract, and intracranial involvement. RDD progressed after multi-agent chemotherapy, but responded to trametinib (0.025mg/kg). Trametinib did not eliminate the mass lesions, but trametinib plus minimal prednisolone (0.1mg/kg) resulted in a good outcome for more than 15months, without significant adverse effects. MAP2K1 p.Lys59del has been described as a germline mutation in a patient with CFC syndrome, but not as a somatic mutation in patients with malignancies. Trametinib may be a promising drug for children with RDD that is refractory to multi-agent chemotherapy. Its long-term efficacy and safety alone and in combination with chemotherapy should be investigated.

Revised Diagnosis From Histiocytic Neoplasm to Optic Chiasm Glioblastoma After Genetic Analysis.

A 46-year-old man presented with left eye blurring. Automated visual field testing showed an incongruous right hemianopia, with sparing of the lower temporal quadrant in the right eye. MRI revealed foci of gadolinium enhancement in the optic chiasm and optic tracts. Serologic testing (including myelin oligodendrocyte glycoprotein and neuromyelitis optica antibodies) and cerebrospinal fluid analysis were negative. Whole-body PET/CT scan found no malignancy. Biopsy of the optic chiasm revealed a moderately cellular neoplasm composed of atypical, discohesive cells with enlarged nuclei, prominent eosinophilic nucleoli, and abundant vacuolated cytoplasm. Immunohistochemical stains for CD68 and S100 were positive, whereas those for GFAP, OLIG2, SOX10, and multiple others were negative, supporting a diagnosis of histiocytic neoplasm. Five weeks later, results became available from next-generation sequencing targeting the coding regions of hundreds of malignancy-associated genes and select introns. Alterations associated with histiocytic neoplasms (i.e. BRAF and MAP2K1 mutations) were absent. However, there was a nonsense mutation in the PTEN gene, a hotspot mutation in the TERT gene promotor, and focal amplifications of the CDK4 and MDM2 genes. Additionally, there was chromosome 6q loss, 7 gain, and 10q loss. Based on these findings, the diagnosis was revised to glioblastoma, IDH-wildtype, CNS WHO grade 4. The patient began treatment with temozolomide while continuing radiation therapy. This case illustrates how next-generation sequencing can at times provide more accurate diagnostic information than standard tissue histopathology.

NFS-19. ATYPICAL PRESENTATION OF GLIOMAS IN ADOLESCENTS WITH NEUROFIBROMATOSIS TYPE 1 (NF1): A CASE SERIES

Abstract BACKGROUND Patients with NF1 are at risk for developing gliomas, usually low-grade in childhood but may be high-grade in adults. In children, the most common sites of disease are the optic pathway and brainstem; tumors in these regions often arise in young children and display histological features characteristic of pilocytic astrocytoma (PA) when biopsied. Typical MRI findings include T2 hyperintense, T1 hypointense lesions with minimal contrast enhancement and no diffusion restriction. Due to the well-established pattern of low-grade tumor formation in children with NF1, as well as the surgically challenging areas in which these tumors develop, low-grade glioma (LGG) therapy is often initiated without histologic confirmation of the diagnosis in classic cases. In cases with atypical disease location, older age at presentation or imaging appearance, a biopsy may be considered to exclude higher-grade lesions. METHODS Retrospective chart review, case series RESULTS Four adolescent patients with NF1 presented with atypical suspected gliomas. All four patients underwent surgical biopsy/resection. Case 1 was a left temporal lesion in the previous radiation field for optic pathway glioma; biopsy confirmed LGG with MAP2K1 mutation and increased focal proliferation index (28%), but methylation did not match with any established classification. The patient progressed through multiple rounds of therapy and succumbed to her tumor. Case 2 was a left occipital lesion; biopsy confirmed PA with CDKN2A deletion. The tumor displayed rapid regrowth, but subsequently stabilized. Case 3 was a right frontal lesion; confirmed PA. The tumor demonstrated some regrowth but then stabilized. Case 4 was a basal ganglia lesion; confirmed PA. The patient has demonstrated stable MRI findings and has not required further intervention. CONCLUSIONS Biopsy yielded helpful prognostic information (additional mutations, proliferation rate) in half of these atypical cases. Biopsy should be carefully considered for NF1 patients with atypical presentation or a history of radiation.

The genomic, transcriptomic, and immunological profile of patients with recurrent/refractory NSCLC.

8039 Background: Lung cancer is the leading cause of cancer-related deaths worldwide, and often presents at advanced stages, with > 50% of patients presenting as stage III or IV. Patients with recurrent stage III NSCLC (R/R) previously treated with definitive chemoradiation and immunotherapy consolidation may have a difference in overall survival compared to de novo stage IV (DN). In this study, we aim to compare the molecular and immune landscapes of these two patient populations to identify potential genomic patterns and biomarkers of resistance. Methods: 3728 NSCLC specimens underwent sequencing of DNA (592-gene panel or whole exome) or RNA (whole transcriptome) or immunohistochemistry at Caris Life Sciences (Phoenix, AZ). Patients were classified as R/R (n = 26) if they received Durvalumab and chemoradiation within 12 months (m) before tissue collection and treated with Pembrolizumab within 6 m after tissue collection. Patients treated with Pembrolizumab within 6 months after tissue collection and had no prior (or post) treatment with Durvalumab and chemoradiation at any point in time were classified as DN (n = 3702). Tumor microenvironment (TME) cell fractions were estimated from bulk RNA sequencing using QuanTIseq. Significance was determined using chi-square, Mann Whitney U and adjusted for multiple comparisons where applicable (q < 0.05). Results: TP53 (91 vs 68%) and KEAP1 (30 vs. 14%, both p < 0.05, q > 0.05) mutation prevalence was higher in R/R, whereas a decreased prevalence of KRAS mutations was noted in this group (13 vs. 33%) as compared to the DN group. Compared to DN patients, R/R patients were associated with an increased prevalence of mutations in BCL2 (4.3 vs. 0%, q < 0.05), BCL9 (4.3 vs. 0.2%, q < 0.05), HNF1A (4.3 vs. 0.2%), TNFAIP3 (4.3 vs. 0.2%), AKT1 (4.3 vs. 0.4%), MAP3K1 (4.3 vs. 0.5%), and SPEN (4.3 vs. 0.6%; all p < 0.05, q > 0.05). Further, copy number amplification of NUTM1 (4.5 vs. 0%), SMO (4.3 vs. 0.5%), CHIC2 (4.5 vs. 0.2%; all q < 0.05), PIK3CA (9 vs. 1.2%) and FLCN (4.5 vs. 0.3%; both p < 0.05, q > 0.05) was more common in R/R compared to DN. R/R TME was associated with decreased B cell (2.9 vs 4.4%, q < 0.05) and regulatory T cell fractions (1.3 vs. 2.6%, p < 0.05, q > 0.05). Conclusions: R/R patient tumors had distinct molecular alterations and immune landscapes, including an increased prevalence of biomarkers associated with immunotherapy resistance ( TP53 and KEAP1 mutations) and lower tumor B- and T reg- cell fractions, which may suggest decreased likelihood of response to immunotherapy compared to patients with DN NSCLC. The RR population had a lower-than-expected percentage of KRASmutations. These distinct molecular differences highlight the need for NGS testing in the recurrent setting, despite initial NGS testing at diagnosis. Molecularly targeted interventions may be options in the future for patients with R/R Stage III NSCLC.

Alliance EAY191-A6: FOLFOX in combination with binimetinib as second-line therapy for patients with advanced biliary tract cancers (BTCs) with MAPK pathway alterations: A ComboMATCH treatment trial.

TPS4196 Background: Advanced BTC patients have poor prognosis. Up to 40% of BTCs have KRAS mutations and are associated with worse overall survival (OS). With a median OS of 7.7 months in KRAS wild-type compared to 1.7 months in KRAS mutated disease, these alterations are independent poor prognostic factors in BTC. Gemcitabine and cisplatin (GC) with or without immunotherapy are often used as 1st-line therapies. However, there is a lack of data on best 2nd-line regimens. mFOLFOX6 (5-fluorouracil [5-FU], leucovorin [LV], oxaliplatin) or liposomal irinotecan+5-FU+LV are options when no biomarkers are found (e.g., MSI-H, BRAFV600E, FGFR-fusions, IDH1-mutation, HER2-overexpression). Prior studies do not demonstrate benefit with MEK inhibitors (MEKi), but none of the studies had biomarker selection. Pre-clinical studies in BTC cell lines suggest synergy between MEKi and 5-FU. Thymidylate synthase (TS )levels induced by 5-FU are downregulated by addition of binimetinib. Early clinical studies show safety and tolerance of this combination. In this study, we will evaluate if the combination of mFOLFOX6+binimetinib improves OS for patients with BTC and MAPK mutations compared to mFOLFOX6 alone in 2nd-line therapy. Methods: EAY191-A6 is a treatment study arm of the NCI ComboMATCH master registration trial EAY191. The A6 trial has a randomized phase II design, enrolling a maximum of 66 patients. Patients with any MAPK pathway mutations except those with available therapies will be eligible. Patient must first enroll to the EAY191 master trial. Local molecular results may be used for enrollment. Submission of tissue at baseline is mandatory. Eligible patients will be randomized 1:1 to mFOLFOX6 vs mFOLFOX6 + binimetinib (45 mg oral twice a day every 14 days). Stratification factors include location and stage of disease. Primary efficacy analysis will compare OS in the intent-to-treat population. If the observed hazard ratio (HR) of experimental arm vs standard of care is < 0.545 (corresponding to an observed increase in OS by 5 months or longer), experimental treatment will be considered superior. An interim futility analysis at 50% of expected events will be conducted. If the observed HR is ≥ 1, experimental treatment will not be considered superior, and accrual maybe suspended. Secondary endpoints include progression-free survival, objective response rate, duration of response, disease control rate and toxicity of treatments. Exploratory objectives include prognostic modeling, correlations of genomic alterations with response or resistance and use of machine learning for outcome prediction. This study is active and open to accrual. Clinical trial information: NCT05564403 .

Mixed histiocytic disorders: Nature versus nurture?

Histiocytic diseases arise from MAPK mutations in myeloid progenitors. Depending on whether the progenitor follows a dendritic cell or macrophage/monocyte lineage the final histology results in Langerhans cell histiocytosis, Rosai-Dorfman disease or Erdheim-Chester disease. Commentary on: Friedman etal. Mixed histiocytic neoplasms: A multicentre series revealing diverse somatic mutations and responses to targeted therapy. Br J Haematol 2024;205:127-137.

Genetic Landscape and Its Prognostic Impact in Children With Langerhans Cell Histiocytosis.

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm that predominantly affects young children. To investigate genetic alterations and their correlation with clinical characteristics and prognosis in pediatric LCH. We performed targeted sequencing to detect mutations in LCH lesions from pediatric patients. A total of 30 genomic alterations in 5 genes of the MAPK pathway were identified in 187 of 223 patients (83.9%). BRAF V600E (B-Raf proto-oncogene, serine/threonine kinase) was the most common mutation (51.6%), followed by MAP2K1 (mitogen-activated protein kinase kinase 1) alterations (17.0%) and other BRAF mutations (13.0%). ARAF (A-Raf proto-oncogene, serine/threonine kinase) and KRAS (KRAS proto-oncogene, GTPase) mutations were relatively rare (2.2% and 0.9%, respectively). Additionally, FNBP1 (formin-binding protein 1)::BRAF fusion and MAP3K10 (mitogen-activated protein kinase kinase 10) mutations A17T and R823C were identified in 1 case each, with possible constitutive activation of ERK1/2 phosphorylation. BRAF V600E was more frequent in patients with risk organ involvement, while MAP2K1 mutation was more prevalent in patients with single-system LCH (P = .001). BRAF V600E was associated with craniofacial bone, skin, liver, spleen, and ear involvement (all P < .05). Patients with other BRAF mutations had a higher proportion of spinal column involvement (P = .006). Univariate analysis showed a significant difference in progression-free survival among the 4 molecular subgroups for patients treated with first-line therapy (P = .02). According to multivariate analysis, risk organ involvement was the strongest independent adverse prognostic factor (hazard ratio, 8.854; P < .001); BRAF or MAP2K1 mutation was not an independent prognostic factor. Most pediatric patients with LCH carry somatic mutations involving the MAPK pathway, correlating with clinical characteristics and outcomes for first-line chemotherapy.

Abstract PO1-13-05: Genomic characteristics and its therapeutic implications in breast cancer patients with detectable molecular residual disease

Abstract Background: Breast cancer constitutes approximately 30% of cancers in women, with a mortality-to-incidence ratio of 15%. While early and middle-stage breast cancer patients can undergo radical surgical resection, postoperative recurrence remains a significant challenge for clinicians. Molecular residual disease (MRD) is the main cause of postoperative recurrence of breast cancer. However, the baseline tumor genomic characteristics and therapeutic implications of breast cancer patients with detectable MRD are still unknown. Methods: In this study, we enrolled 80 patients with breast cancer who underwent next-generation sequencing (NGS)-based genetic testing of 1,021 cancer-related genes performed on baseline tumor and postoperative plasma from Army Specialty Medical Center between June 2017 and January 2023. The criteria for the patient’s enrollment were: (1) pathological diagnosis as breast cancer, (2) no distal metastasis, (3) radical surgery and R0 resection, (4) 1021 cancer-related gene testing of the tumor, (5) plasma MRD testing performed within 3 months after surgery and before adjuvant therapy. Results: A total of 18 patients in our cohort had detectable MRD. Baseline clinical characteristics found that patients with higher clinical stages were more likely to have detectable MRD. Analysis of single nucleotide variations and small insertions/deletions in baseline tumors showed that somatic mutations in MAP3K1, ATM, FLT1, GNAS, POLD1, SPEN, and WWP2 were significantly enriched in patients with postoperative MRD. Oncogenic signaling pathway analysis revealed that alteration of the Cell cycle pathway was more likely to occur in patients with detectable MRD (p=0.0125). Mutational signature analysis showed that defective DNA mismatch repair and activation-induced cytidine deaminase (AID) mediated somatic hypermutation (SHM) were associated with detectable MRD. Somatic copy number variation analysis found that amplification of CDKN2A, HOXB13, PPM1D, MPL, and VHL was significantly enriched in patients with detectable MRD. According to the OncoKB database, 77.8% (14/18) of patients with detectable MRD had U.S. Food and Drug Administration-approved mutational biomarkers and targeted therapy. Conclusion: For the first time, our study reports genomic characteristics of breast cancer patients with detectable MRD. The tumor biology is probably the main driver of detectable MRD. We also found the vast majority of patients with detectable MRD have the opportunity to access targeted therapy. Keywords: Breast cancer, MRD, Genomic character, Cell cycle pathway, Defective DNA mismatch repair, Activation-induced cytidine deaminase Figure 1. Somatic mutational landscape and clinical actionability of breast cancer patients with detectable MRD A. Oncoplot of top 20 genes altered in patients with detectable MRD. B. Forest plot of different mutant genes between patients with detectable and undetectable MRD. OR means odds ratio. Inf means infinity. ＊ means P-value &amp;lt; 0.05. C. The ten cancer-related signaling pathways were affected by somatic mutations both in patients with detectable and undetectable MRD. ＊ means P-value &amp;lt; 0.05. D&amp;E. The fraction and etiology of each signature in patients with detectable (D) or undetectable (E) MRD. F. The number of patients with detectable MRD in different actionable alterations. gBRCA1 means germline BRCA1 mutation. sBRCA1 means somatic BRCA1 mutation. sBRCA2 means somatic BRCA2 mutation. TMB-H means TMB-High. Citation Format: Xu Yan, Shu Zhang, Lu zhou, Yan Jiang, Jing Xu, Gang Zhang, Lu Shen. Genomic characteristics and its therapeutic implications in breast cancer patients with detectable molecular residual disease [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-13-05.

Abstract PO4-26-03: Collagen deposition in the breast cancer microenvironment correlates with ER-positive, Histological Grade I and low proliferation tumors

Abstract Breast cancer is a highly heterogeneous neoplasm both at the molecular and histological levels. Breast cancer cells present extremely high levels of genetic heterogeneity concerning mutational burden, copy number variations (CNVs) and epigenetic signatures. While this level of heterogeneity is well established, other layers of heterogeneity, such as tumor microenvironment (TME) heterogeneity, remains to be elucidated. TME in breast cancer is an intricate network encompassing tumor cells, “normal” stroma cells such as fibroblasts, lymphocytes, and a plethora of extracellular matrix (ECM) proteins produced either by cancer cells or stromal cells. These three interacting modules (cancer cells, stromal cells and the ECM) can affect each other in a reciprocal way with profound effects on patient prognosis and treatment outcome. Major protein components of the TME are ECM-related collagens, that are produced by breast cancer cells or/and cancer associated fibroblasts. The ECM collagen in breast cancer, that is mainly composed of collagen types I, III and V, has multiple roles modulating tumor growth, cancer cell invasiveness and metastasis. Here by Masson Trichrome and Immunohistochemistry/Aniline Blue co-stains for collagen fibers and proliferation index (Ki-67) in breast cancer FFPE tissue samples, we identified a statistically significant correlation between collagen deposition and Estrogen Receptor (ER)) status (p&amp;lt; 0.05, proliferation index (p&amp;lt; 0.01) and histological Grade (p=0.01). Further, in order to expand and support our findings, we analyzed the METABRIC study through the cBioPortal hub in relevance to collagen genes and multiple clinicopathological parameters. We were able to identify a coregulated subset of collagen genes that presented a positive correlation with ER-positive (p&amp;lt; 10−10, q&amp;lt; 10−10), low proliferating (p&amp;lt; 10−10, q&amp;lt; 10−10), Grade I (p=2.35e−9, q&amp;lt; 1.07e−8) group of breast cancer cases, supporting our findings. In addition, analyses of collagen-high patients from the METABRIC study indicated that most cases presented with PIK3CA, CBFB and MAP3K1 mutations, while through the g.Profiler software we identified collagen-high relevant gene signatures that encompassed gene ontology terms related to tissue development, extracellular matrix organization and cell migration. Collectively, our preliminary results indicate that ECM collagen deposition in breast cancer is characteristic of low-grade tumors with a better differentiation and possibly with a favorable prognosis. Citation Format: Angelos Koutras, Chaido Sirinian, Olga Bogri, Martha Nifora, Maria Theakou, Soren Degn, Ioannis Mouratidis, Dimitrios Chaniotis, Stavros Peroukidis, Ilias Georgakopoulos-Soares, Anastasios Papanastasiou. Collagen deposition in the breast cancer microenvironment correlates with ER-positive, Histological Grade I and low proliferation tumors [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-26-03.

Clonal expansion of shared T cell receptors reveals the existence of immune commonality among different lesions of synchronous multiple primary lung cancer

The increase in the detection rate of synchronous multiple primary lung cancer (MPLC) has posed remarkable clinical challenges due to the limited understanding of its pathogenesis and molecular features. Here, comprehensive comparisons of genomic and immunologic features between MPLC and solitary lung cancer nodule (SN), as well as different lesions of the same patient, were performed. Compared with SN, MPLC displayed a lower rate of EGFR mutation but higher rates of BRAF, MAP2K1, and MTOR mutation, which function exactly in the upstream and downstream of the same signaling pathway. Considerable heterogeneity in T cell receptor (TCR) repertoire exists among not only different patients but also among different lesions of the same patient. Invasive lesions of MPLC exhibited significantly higher TCR diversity and lower TCR expansion than those of SN. Intriguingly, different lesions of the same patient always shared a certain proportion of TCR clonotypes. Significant clonal expansion could be observed in shared TCR clonotypes, particularly in those existing in all lesions of the same patient. In conclusion, this study provided evidences of the distinctive mutational landscape, activation of oncogenic signaling pathways, and TCR repertoire in MPLC as compared with SN. The significant clonal expansion of shared TCR clonotypes demonstrated the existence of immune commonality among different lesions of the same patient and shed new light on the individually tailored precision therapy for MPLC.

Genomic Characteristics and Its Therapeutic Implications in Breast Cancer Patients with Detectable Molecular Residual Disease.

Molecular residual disease (MRD) is the main cause of postoperative recurrence of breast cancer. However, the baseline tumor genomic characteristics and therapeutic implications of breast cancer patients with detectable MRD after surgery are still unknown. In this study, we enrolled 80 patients with breast cancer who underwent next-generation sequencing-based genetic testing of 1,021 cancer-related genes performed on baseline tumor and postoperative plasma, among which 18 patients had detectable MRD after surgery. Baseline clinical characteristics found that patients with higher clinical stages were more likely to have detectable MRD. Analysis of single nucleotide variations and small insertions/deletions in baseline tumors showed that somatic mutations in MAP3K1, ATM, FLT1, GNAS, POLD1, SPEN, and WWP2 were significantly enriched in patients with detectable MRD. Oncogenic signaling pathway analysis revealed that alteration of the Cell cycle pathway was more likely to occur in patients with detectable MRD (p=0.012). Mutational signature analysis showed that defective DNA mismatch repair and activation-induced cytidine deaminase (AID) mediated somatic hypermutation (SHM) were associated with detectable MRD. According to the OncoKB database, 77.8% (14/18) of patients with detectable MRD had U.S. Food and Drug Administration-approved mutational biomarkers and targeted therapy. Our study reports genomic characteristics of breast cancer patients with detectable MRD. The cell cycle pathway, defective DNA mismatch repair, and AID-mediated SHM were found to be the possible causes of detectable MRD. We also found the vast majority of patients with detectable MRD have the opportunity to access targeted therapy.

P18 Giant Periocular Juvenile Xanthogranulomas Treated with Trametinib

Abstract Juvenile Xanthogranuloma (JXG), the commonest type of non-Langerhans cell histiocytosis, is regarded as a benign self-limiting condition of infancy, characterised by asymptomatic yellow brown papulonodular lesions, usually confined to the skin but occasionally affecting the eyes or internal organs. Skin lesions characteristically regress spontaneously within 3-6 years. We describe an unusually aggressive cutaneous presentation requiring input from paediatric oncology. A 6 year old boy presented with extensive soft yellowish papules, plaques and nodules particularly around the eyes but also over the chest and leg. Biopsy confirmed the clinical diagnosis of JXG. The lesions enlarged progressively with new lesions appearing, causing significant distortion of the upper and lower eyelids with reduced ability to open the eyes, discomfort and distress. Treatment was started with topical steroids, progressing to intralesional and systemic steroids, but with minimal effect. In view of the severity, vinblastine and subsequently cytarabine were added, again with limited benefit. The periocular lesions were surgically debulked and he was commenced on Trametinib (a MEK inhibitor) with a good response. Now aged 9 years, and the patient displayed a favourable clinical response after 3 months of being on Trametinib. JXG rarely requires treatment, but there is no recognised therapy for the occasional problematic lesions. In this case trametinib was effective and well-tolerated. The efficacy of trametinib in histiocytosis has been attributed to the presence of activating BRAF and MAP2K1 mutations. Genetic analysis of JXG may guide future therapies.

Prognostic Value of IGFBP6 in Breast Cancer: Focus on Glucometabolism.

IGFBP6, a member of the IGF binding protein (IGFBP) family, is a specific inhibitor of insulin-like growth factor II (IGF-II) and can inhibit the growth of malignant tumors overexpressing IGF-II. Type 2 diabetes (T2D) is a basic disorder of glucose metabolism that can be regulated by IGF-related pathways. We performed bioinformatics analysis of the TCGA database to explore the possible mechanism of IGFBP6 in breast cancer (BC) metabolism and prognosis and collected clinical samples from BC patients with and without T2D to compare and verify the prognostic effect of IGFBP6. In our study, the levels of IGFBP1-6 were positively correlated with overall survival (OS) in patients with breast cancer. IGFBP6 was upregulated in estrogen receptor (ER)-positive BC, and ER-positive and progesterone receptor (PR) positive patients had a higher expression level of IGFBP6 than ER-negative and PR-negative patients. IGFBP6 could be used as an independent prognostic factor in BC. The expression of IGFBP6 was decreased in BC tissue, and BC tissue from patients with T2D had lower IGFBP6 expression levels than BC tissue from patients without T2D. IGFBP6 is mainly involved in the PI3K-Akt and TGF-β signaling pathways and tumor microenvironment regulation. In terms of metabolism, the expression of IGFBP6 was negatively correlated with that of most glucose metabolism-related genes. IGFBP6 expression was mainly correlated with mutations in TP53, PIK3CA, CDH1, and MAP3K1. In addition, the upregulation of IGFBP6 in BC increased the drug sensitivity to docetaxel, paclitaxel and gemcitabine. Overall, these results indicated that high expression of IGFBP6 is associated with a good prognosis in BC patients, especially in those without T2D. It is not only involved in the maintenance of the tumor microenvironment in BC but also inhibits the energy metabolism of cancer cells through glucose metabolism-related pathways. These findings may provide a new perspective on IGFBP6 as a potential prognostic marker for BC.