Molecular Tumors Research Articles

A Phase II Study of Fulvestrant plus Abemaciclib in Hormone Receptor-Positive Advanced or Recurrent Endometrial Cancer.

Inhibition of the cyclin D-cyclin dependent kinase (CDK)4/6-INK4-retinoblastoma pathway can overcome acquired or de novo treatment resistance to endocrine monotherapy. Responses to endocrine monotherapy in advanced endometrial cancer (EC) are suboptimal, perhaps due to genomic alterations that promote estrogen receptor (ER)-independent cyclin D1-CDK4/6 activation. We hypothesized that addition of abemaciclib, a CDK4/6 kinase inhibitor, to antiestrogen therapy with fulvestrant will be an effective therapeutic strategy in patients with advanced or recurrent EC. In this phase II study, patients with advanced or recurrent EC received 150 mg of abemaciclib orally twice daily with 500 mg of fulvestrant intramuscularly monthly with a 2-week loading dose. Eligibility included ER or progesterone receptor expression ³1% by immunohistochemistry, measurable disease, £2 prior lines of chemotherapy, and £1 prior line of hormonal therapy. The primary endpoint was objective response rate (ORR) by RECIST v1.1. Twenty-seven patients initiated therapy and 25 were evaluable for efficacy. Eleven patients achieved partial response; 10 responses (91%) were in copy number-low/no specific molecular profile tumors, 1 (9%) was in a microsatellite instability-high tumor, and no responses were observed in copy number-high/TP53abnormal tumors. The ORR was 44% (90% CI, 27.0%-62.1%). Median duration of response was 15.6 months. Median progression-free survival was 9.0 months (90% CI: 1.8-20.4). The most common grade ³3 treatment-related adverse events were neutropenia (26%) and anemia (19%); no new safety signals were identified. The combination of abemaciclib and fulvestrant has promising activity with durable responses in advanced or recurrent EC; a randomized trial is planned.

Abstract C100: Defining the role of Hedgehog, Notch, and Wnt signaling pathways in aggressive lethal prostate cancer of Hispanic men

Abstract Background: Hispanic American (HA) men with prostate cancer (PC) are more likely to have more aggressive and advanced diseases and greater mortality rates compared to non-Hispanic white (NHW) men. Resistance to the current anticancer therapy is the major hurdle that leads to poor clinical outcomes. Hedgehog, Notch, and Wnt signaling pathways play a crucial role in development, progression, and resistance to the various anticancer therapies. Here, we characterized the enrichment of Hedgehog, Notch, and Wnt signaling pathways and molecular tumors differences between HA and NHW patients. Methods: Our data consist of 88 PC tumors samples (HA=34, NHW=54) obtained from treatment-naive metastatic hormone-sensitive prostate cancer (mHSPC) that were analyzed by next-generation sequencing (592, NextSeq; Whole Exome Sequencing, NovaSeq) and Whole Transcriptome Sequencing (WTS; NovaSeq) (Caris Life Sciences, Phoenix, AZ). Pathway enrichment was determined by Gene Set Enrichment Analysis (GSEA, Broad Institute) by measurable TPM (transcripts per kilobase million). The medical records were reviewed in a deidentified fashion for clinical features. Statistical significance was determined using chi-square and Mann-Whitney U (p<0.05). Results: HA PC had enrichment of Hedgehog signaling (NES: 1.45, FDR=0.04), Notch signaling (NES: 1.41, FDR=0.07), and Wnt/β-catenin signaling (NES: 1.38, FDR=0.11) pathways compared to NHW tumors. HA tumors had higher expression of genes (HES1, Notch1, WNT1, WNT2; FC:1.1-2.5) associated with crosstalk between Hedgehog, Notch, and Wnt/β- catenin signaling pathways (all p<0.05). Moreover, HA tumors had higher expression of stemness (ALDH1A2, ALDH1A1, PROM1; FC: 1.7-3.0), drug efflux (ABCC1, ABCB1; FC: 1.1- 1.5), epithelial to mesenchymal transition (EMT) (TWIST1, MMP2; FC: 1.1-1.5), cell cycle (CCND2; FC: 1.2), inhibition of apoptosis (BIRC2, XIAP; FC: 1.1) and epigenetic (EP300, TET1, TET2; FC: 1.3-1.4) related genes compared to NHW tumors (all p<0.05). HA PC had higher frequency of Hedgehog and Wnt/β-catenin associated SPOP (16% vs 6.6%, p=0.2) and CTNNB1 (12% vs 2.2%, p=0.1) mutation compared to NHW PC. Conclusion: These results demonstrate that tumors from HA patients had enrichment of oncogenic Hedgehog, Notch, and Wnt/β-catenin signaling pathways, higher expression of stemness, drug efflux, EMT, cell cycle, inhibition of apoptosis and epigenetic-related genes, and mutations directly involved in activating the Hedgehog and Wnt/β-catenin signaling pathways. Together, these findings suggest that tumors from HA patients are enriched for gene signatures that promote cancer progression and therapy resistance. Additional research on collaboration and crosstalk between Hedgehog, Notch, and Wnt/β-catenin signaling pathways may help in designing better therapeutic strategies for HA men with mHSPC. Citation Format: Alejandro Recio-Boiles, Sachin Kumar Deshmukh, Ricardo J. Estrada-Mendizabal, Kenneth Barker, Sharon Wu, Joanne Xiu, Milan Radovich, Elisabeth I. Heath, Rana McKay, Juan Chipollini, Cynthia K. Miranti. Defining the role of Hedgehog, Notch, and Wnt signaling pathways in aggressive lethal prostate cancer of Hispanic men [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C100.

Detailed Profiling of the Tumor Microenvironment in Ethnic Breast Cancer, Using Tissue Microarrays and Multiplex Immunofluorescence.

Breast cancer poses a global health challenge, yet the influence of ethnicity on the tumor microenvironment (TME) remains understudied. In this investigation, we examined immune cell infiltration in 230 breast cancer samples, emphasizing diverse ethnic populations. Leveraging tissue microarrays (TMAs) and core samples, we applied multiplex immunofluorescence (mIF) to dissect immune cell subtypes across TME regions. Our analysis revealed distinct immune cell distribution patterns, particularly enriched in aggressive molecular subtypes triple-negative and HER2-positive tumors. We observed significant correlations between immune cell abundance and key clinicopathological parameters, including tumor size, lymph node involvement, and patient overall survival. Notably, immune cell location within different TME regions showed varying correlations with clinicopathologic parameters. Additionally, ethnicities exhibited diverse distributions of cells, with certain ethnicities showing higher abundance compared to others. In TMA samples, patients of Chinese and Caribbean origin displayed significantly lower numbers of B cells, TAMs, and FOXP3-positive cells. These findings highlight the intricate interplay between immune cells and breast cancer progression, with implications for personalized treatment strategies. Moving forward, integrating advanced imaging techniques, and exploring immune cell heterogeneity in diverse ethnic cohorts can uncover novel immune signatures and guide tailored immunotherapeutic interventions, ultimately improving breast cancer management.

Factors delaying non-metastatic breast cancer adjuvant therapy and impact on prognosis in a cohort of Brazilian women.

To identify factors associated with delays in beginning adjuvant therapy and prognosis impacts on non-metastatic breast cancer patients. This assessment comprised a prospective cohort study concerning breast cancer patients treated at a public oncology centre. A time interval of ≥60 days between surgery and the beginning of the first adjuvant treatment was categorised as a delay. Factors associated with delays were evaluated through logistic regression analysis and the prognosis effects were assessed by a Cox regression analysis. The median time interval between surgery and the first adjuvant treatment for the 401 women included in this study was of 57.0 days (37.0-93.0). Independent factors associated with delays comprised not presenting an overexpression of the HER-2 protein, not having undergone neoadjuvant chemotherapy, and having undergone chemotherapy or other therapeutic modalities other than hormone therapy and chemotherapy as the first adjuvant treatment. Delays did not affect recurrence, distant metastasis, or death risks. Factors associated with recurrence and distant metastasis risks comprised a clinical staging ≥2B, having undergone neoadjuvant chemotherapy, presenting the luminal molecular subtype B and triple-negative tumours, and having children. Factors associated with death comprised triple-negative molecular tumours and neoadjuvant chemotherapy. Delays in beginning adjuvant treatment did not affect the prognosis of non-metastatic breast cancer patients. Clinical and treatment-related factors, on the other hand, were associated with delays, and recurrence, distant metastasis, and death risks.

Patterns of cytotoxic T-cell densities in immunogenic endometrial cancers reveal a potential mechanism for differences in immunotherapy efficacy

ObjectiveTo explore the impact of molecular subtype in endometrial cancer (EC) on CD8+T cell densities. Furthermore, this work will test the assumption that all mismatch repair deficient (MMRd) tumours are...

Abstract PO3-25-07: Characterization of tertiary lymphoid structures and its association with response to immune checkpoint inhibitors in triple negative breast cancer using spatial transcriptomics

Abstract Background Tertiary lymphoid structures (TLS) are ectopic lymphoid organs playing a role in adaptive antitumor immune response. They were shown to be associated with favorable outcome and appears to be a promising biomarker for response to immune checkpoint inhibitors (ICI). Yet, there is no consensus for their detection and quantification. Here we aimed to derive a specific TLS signature using high resolution spatial transcriptomics data from a large series of triple negative breast cancer (TNBC) samples and to assess its clinical relevance including response to ICI. Methods Spatial transcriptomics (ST) was performed on a series of 94 early-stage TNBC surgical samples with detailed clinicopathological and outcome data. TLS and tumor infiltrating lymphocytes (TILs) were scored using hematoxylin and eosin and double immunohistochemistry (CD3/CD20) stained slides by a dedicated breast pathologist. Regression based on morphological annotations and deconvolution methods estimated the fraction of gene expression related to TLS in each ST spot allowing to derive specific TLS signature. Its prognostic and predictive value of response to ICI was assessed using publicly available breast cancer (METABRIC, SCAN-B, and I-SPY2) and other tumor type datasets treated with ICI (Bareche et al. Ann Oncol, 2022) from bulk gene expression data. Results Deconvolution of the TLS compartments using the ST gene expression data showed that TLS are enriched in all B cell subsets, CD4+ (central) memory and naïve T cells, as well as mast cells. A functional analysis showed an enrichment of ‘vascular endothelial cell proliferation’, ‘mitotic G2/M transition checkpoint’, ‘V/D/J recombination’ and ‘regulation of cell chemotaxis to fibroblast growth factor’ suggesting that TLS aggregates are associated with angiogenesis, immune cell proliferation, adaptative humoral response and tissue remodeling. A comparison of gene expression data between TLS and non-aggregated TILs led to the development of a specific TLS gene signature comprising B and T cell-specific genes, immunoglobulin genes as well as genes associated with TLS initiation. Its projection on tumor slides overlapped with the regions annotated as TLS by the pathologist, demonstrating its specificity for TLS detection. As expected, the highest levels of the TLS signature were observed in the immunomodulatory TNBC molecular subtype and fully inflamed tumors, whereas the lowest levels were observed in the mesenchymal molecular subtype and immune desert tumors (p< 0.05). Of note, high levels of the TLS signature were associated with better prognosis in TNBC patients from METABRIC (p=6.5 10−5) and SCAN-B datasets (p=1.6 10−3) as well as with higher pathological complete response rates in all breast cancer patients treated with neoadjuvant pembrolizumab in the I-SPY2 study (p=0.026). Similar results were found in other tumor types treated with immunotherapy in the metastatic setting including metastatic melanoma, pancreatic and bladder cancers (PFS, p=6 10−6). Of interest, the TLS signature outperformed the predictive value of other immune-related signatures including TILs suggesting a key role of TLS in obtaining a sustainable, adaptive antitumor immune response in the vicinity of the tumor area. Conclusion By leveraging the potential of spatial transcriptomics, we have successfully developed a unique TLS gene signature that demonstrates a strong correlation with the response to ICI in breast cancer and various other tumor types. This TLS gene signature outperforms other immune biomarkers, underscoring the pivotal role of TLS in eliciting a robust antitumor immune response. The universality of this TLS signature makes it a potent biomarker capable of identifying patients who would benefit from immunotherapy, pending further validation. Citation Format: Xiaoxiao Wang, David Venet, Frédéric Lifrange, Denis Larsimont, Mattia Rediti, Linnea Stenbeck, Floriane Dupont, Ghizlane Rouas, Andrea Joaquin Garcia, David Gacquer, Ligia Craciun, Laurence Buisseret, Nayanika Bhalla, Yuvarani Masarapu, Kim Thrane, Eva Gracia Villacampa, Lovisa Franzén, Sami Saarenpää, Linda Kvastad, Joakim Lundeberg, Françoise Rothé, Christos Sotiriou. Characterization of tertiary lymphoid structures and its association with response to immune checkpoint inhibitors in triple negative breast cancer using spatial transcriptomics [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 PO3-25-07.

Molecular profile is a strong predictor of the pattern of recurrence in patients with endometrial cancer

ObjectivesTo investigate the pattern of first recurrence of disease in patients with endometrial cancer according to molecular classification, and to assess the independent role of molecular profiling in each type...

FPFT-2216, a Novel Anti-lymphoma Compound, Induces Simultaneous Degradation of IKZF1/3 and CK1α to Activate p53 and Inhibit NFκB Signaling.

We found potential vulnerability to CK1α degradation in certain lymphoma cells refractory to IKZF1/3 degraders. Targeting CK1α with FPFT-2216 could inhibit the growth of these cells by activating p53 signaling. Our study demonstrates the potential therapeutic application of CK1α degraders, such as FPFT-2216, for treating lymphoma.

A phase 1, first-in-human, dose-escalation and expansion study of FX-909 in patients with advanced solid malignancies, including advanced urothelial carcinoma.

TPS709 Background: High Expression of Peroxisome proliferator-activated receptor gamma (PPARG), a nuclear receptor-family transcription factor, drives the initiation and development of UC in luminal molecular subtype tumors. Genetic profiling of UC has identified recurrent oncogenic alterations in the PPARG transcriptional complex, including focal amplification, missense mutations, and fusions in the heterodimeric partner of PPARG, the retinoid X receptor alpha (RXRA). High levels of PPARG expression and recurrent oncogenic alterations are observed in other solid malignancies including colorectal, gastroesophageal, pancreatic and lung cancers. FX-909 is an oral, first-in-class, new molecular agent that specifically, potently, and covalently modifies PPARG to mediate basal and ligand-activated transcription. Treatment of genetically defined UC xenografts with FX-909 has shown an 84% tumor growth inhibition (TGI) at a dose expected to be equivalent to 50 mg dose in humans, which is the starting dose in this clinical study. Methods: FX-909-CLINPRO-1 (NCT05929235) is a first-in-human, multicenter, open-label Phase 1 study to evaluate the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and preliminary clinical activity of FX-909 given orally in patients with advanced solid malignancies. Patients enrolled in the trial must have ECOG performance status ≤2 and must be ≥ 18 years of age. Initially, FX-909 will be given once daily to patients with any advanced solid malignancy in a dose-escalation phase (Part A) utilizing a 3+3 design. Five dose cohorts of 3 to 6 patients are planned. At the time of submission, three patients are enrolled in Part A- cohort one, 50mg. Additional patients will be allowed to backfill to previously cleared dose levels that demonstrate therapeutically relevant exposures or evidence of clinical activity. Once a RP2D has been determined, a monotherapy expansion phase (Part B) will proceed in a Simon 2-stage design in patients with locally advanced (unresectable) or metastatic UC with measurable disease and tumors harboring defined genetic alterations in PPARG, RXRA and FGFR3 (Motley et al, 2022). In stage 1, up to 19 evaluable patients will be enrolled. If ≥4 objective responses are observed, enrollment will continue into Stage 2 with an additional 14 evaluable patients. One treatment cycle is 28 days. Dose expansion will evaluate the safety, PK/PD profile, and antitumor activity of FX-909 at the RP2D. Exploratory objectives include the evaluation patient selection biomarkers from tissue and blood samples. FX-909 clinical activity will be assessed using RECIST v1.1 criteria. The study is currently enrolling patients in the US. Clinical trial information: NCT05929235 .

Reclassifying Papillary, Oncocytic and Chromophobe Renal Tumours Based on the 5 < sup > th < /sup > Who Classification 2022.

The classification of renal tumors is expanding with the addition of new molecular entities in the 5th World Health Organization classification. Apart from this, the major updates in the definition of papillary renal cell carcinoma are that these tumors are no longer subtyped into type 1 and type 2. In oncocytic tumors, the new molecularly defined renal tumors, emerging and novel entities need to be considered in the diagnosis of oncocytic and chromophobe renal tumors. This is a retrospective study to review and reclassify papillary, oncocytic, and chromophobe renal tumors based on the new WHO classification and correlate with clinical data, gross, microscopic features, and immunohistochemistry markers. A total of thirteen cases were reviewed and the tumor grade was changed for three out of four cases of papillary renal cell carcinoma and a single case was recategorized and graded. In nine cases of oncocytic and chromophobe renal tumors, the diagnoses were modified in 3 cases. Newly defined molecular renal tumors require advanced immunohistochemistry markers and molecular tests. This poses diagnostic challenges to pathologists practicing in low resource settings where molecular tests are not available.

Identification of aberrant luminal progenitors and mTORC1 as a potential breast cancer prevention target in BRCA2 mutation carriers.

Inheritance of a BRCA2 pathogenic variant conveys a substantial life-time risk of breast cancer. Identification of the cell(s)-of-origin of BRCA2-mutant breast cancer and targetable perturbations that contribute to transformation remains an unmet need for these individuals who frequently undergo prophylactic mastectomy. Using preneoplastic specimens from age-matched, premenopausal females, here we show broad dysregulation across the luminal compartment in BRCA2mut/+ tissue, including expansion of aberrant ERBB3lo luminal progenitor and mature cells, and the presence of atypical oestrogen receptor (ER)-positive lesions. Transcriptional profiling and functional assays revealed perturbed proteostasis and translation in ERBB3lo progenitors in BRCA2mut/+ breast tissue, independent of ageing. Similar molecular perturbations marked tumours bearing BRCA2-truncating mutations. ERBB3lo progenitors could generate both ER+ and ER- cells, potentially serving as cells-of-origin for ER-positive or triple-negative cancers. Short-term treatment with an mTORC1 inhibitor substantially curtailed tumorigenesis in a preclinical model of BRCA2-deficient breast cancer, thus uncovering a potential prevention strategy for BRCA2 mutation carriers.

Apocrine carcinoma of the breast: Review

Abstract Apocrine carcinoma of the breast is a rare subtype of breast carcinoma, which only presents as 4% among patients with breast cancer. The percentage varies based on the diagnostic criteria used by each institution to classify apocrine carcinoma. Several confusing terms used in previous studies, including apocrine ductal carcinoma in situ (ADCIS), apocrine morphology in lobular carcinoma in situ (Apocrine LCIS), apocrine-like invasive carcinoma, pure apocrine carcinoma, molecular apocrine tumors (MATs), and triple-negative apocrine carcinoma of the breast (TNAC). The treatment, prognosis, and molecular profiles are also diverse. Pure apocrine carcinoma has stricter criteria for diagnosis, requiring more than 90% of cells showing apocrine morphology and classic IHC characteristics of ER-negative, PR-negative, and AR-positive in at least 10% of tumor cell nuclei. Research related to prognosis is diverse due to the difficulty of unifying the diagnostic criteria. Current evidence of treatment is geared toward the use of neoadjuvant chemotherapy and anti-androgen therapy when AR is present, accompanied by other treatments if biomarkers are present, such as HER2, PI3K, or CDK4/6. This article focuses on clearly summarizing different subtypes and management of apocrine carcinoma of the breast.

The 2021 WHO Classification for Gliomas and Implications on Imaging Diagnosis: Part 1-Key Points of the Fifth Edition and Summary of Imaging Findings on Adult-Type Diffuse Gliomas.

The fifth edition of the World Health Organization (WHO) classification of central nervous system tumors published in 2021 advances the role of molecular diagnostics in the classification of gliomas by emphasizing integrated diagnoses based on histopathology and molecular information and grouping tumors based on genetic alterations. Importantly, molecular biomarkers that provide important prognostic information are now a parameter for establishing tumor grades in gliomas. Understanding the 2021 WHO classification is crucial for radiologists for daily imaging interpretation as well as communication with clinicians. Although imaging features are not included in the 2021 WHO classification, imaging can serve as a powerful tool to impact the clinical practice not only prior to tissue confirmation but beyond. This review represents the first of a three-installment review series on the 2021 WHO classification for gliomas, glioneuronal tumors, and neuronal tumors and implications on imaging diagnosis. This Part 1 Review focuses on the major changes to the classification of gliomas and imaging findings on adult-type diffuse gliomas. EVIDENCE LEVEL: 3. TECHNICAL EFFICACY: Stage 3.

The 2021 WHO Classification for Gliomas and Implications on Imaging Diagnosis: Part 2-Summary of Imaging Findings on Pediatric-Type Diffuse High-Grade Gliomas, Pediatric-Type Diffuse Low-Grade Gliomas, and Circumscribed Astrocytic Gliomas.

The fifth edition of the World Health Organization (WHO) classification of central nervous system tumors published in 2021 advances the role of molecular diagnostics in the classification of gliomas by emphasizing integrated diagnoses based on histopathology and molecular information and grouping tumors based on genetic alterations. This Part 2 review focuses on the molecular diagnostics and imaging findings of pediatric-type diffuse high-grade gliomas, pediatric-type diffuse low-grade gliomas, and circumscribed astrocytic gliomas. Each tumor type in pediatric-type diffuse high-grade glioma mostly harbors a distinct molecular marker. On the other hand, in pediatric-type diffuse low-grade gliomas and circumscribed astrocytic gliomas, molecular diagnostics may be extremely complicated at a glance in the 2021 WHO classification. It is crucial for radiologists to understand the molecular diagnostics and imaging findings and leverage the knowledge in clinical practice. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 3.

Single-nucleus and Spatially Resolved Intratumor Subtype Heterogeneity in Bladder Cancer

BackgroundCurrent bulk transcriptomic classification systems for bladder cancer do not consider the level of intratumor subtype heterogeneity. ObjectiveTo investigate the extent and possible clinical impact of intratumor subtype heterogeneity across early and more advanced stages of bladder cancer. Design, setting, and participantsWe performed single-nucleus RNA sequencing (RNA-seq) of 48 bladder tumors and additional spatial transcriptomics for four of these tumors. Total bulk RNA-seq and spatial proteomics data were available from the same tumors for comparison, along with detailed clinical follow-up of the patients. Outcome measurements and statistical analysisThe primary outcome was progression-free survival for non–muscle-invasive bladder cancer. Cox regression analysis, log-rank tests, Wilcoxon rank-sum tests, Spearman correlation, and Pearson correlation were used for statistical analysis. Results and limitationsWe found that the tumors exhibited varying levels of intratumor subtype heterogeneity and that the level of subtype heterogeneity can be estimated from both single-nucleus and bulk RNA-seq data, with high concordance between the two. We found that a higher class 2a weight estimated from bulk RNA-seq data is associated with worse outcome for patients with molecular high-risk class 2a tumors. The sparsity of the data generated using the DroNc-seq sequencing protocol is a limitation. ConclusionsOur results indicate that discrete subtype assignments from bulk RNA-seq data may lack biological granularity and that continuous class scores may improve clinical risk stratification of patients with bladder cancer. Patient summaryWe found that several molecular subtypes can exist within a single bladder tumor and that continuous subtype scores can be used to identify a subgroup of patients with poor outcomes. Use of these subtype scores may improve risk stratification for patients with bladder cancer, which can help in making decisions on treatment.

PI3K/AKT/mTOR inhibitors as potential extracellular matrix modulators for targeting EMT subtype gastric tumors.

Targeting the extracellular matrix (ECM) is considered as a promising strategy in cancer therapeutics. This study was designed to identify the potential ECM modulators for gastric cancer therapeutics. Exploration of the expression profiles of gastric tumors revealed the elevated expression of ECM genes in gastric tumor tissues compared to the adjacent normal tissues with increased expression in diffuse subtype gastric tumors and specifically in epithelial to mesenchymal transition (EMT) molecular subtype tumors. Consensus ECM gene set was derived from the expression profiles of gastric tumors. The correlative analysis was performed between the expression pattern of the ECM gene set and the drug sensitivity pattern of a panel of drugs across gastric cancer cell lines. Negative correlation between the expression of ECM genes and sensitivity of a number of drugs targeting PI3K/mTOR signaling, chromatin histone acetylation and ABL signaling was observed. These pathways are known for their role in cell-mediated adhesion, differentiation and epithelial to mesenchymal transition. The current results reveal the possibility of using PI3K/AKT/mTOR modulators for targeted gastric cancer therapy in patients with dysregulated ECM.

Abstract P2-03-04: Long-Term Benefit from Adjuvant Tamoxifen in Luminal A and Luminal B Breast Cancer Patients

Abstract Background: The risk for patients with estrogen receptor (ER)-positive breast cancer remains stable decades after primary diagnosis, with a large proportion of distant metastatic events occurring late. Thus, long-term follow-up studies are essential to understand true treatment benefit. Tamoxifen (TAM) therapy is a fundamental endocrine treatment for ER-positive breast cancer. We have previously shown a long-term tamoxifen therapy benefit for patients with less aggressive tumor characteristics in ER-positive/HER2-negative patients. However, ER-positive breast cancer is highly heterogenous and can be separated into different molecular subpopulations that behave differently during extended follow-up. The long-term tamoxifen benefit by molecular subtype is largely unexplored. We therefore aimed to investigate the long-term benefit from tamoxifen by clinically used tumor characteristics in Luminal A vs Luminal B patients in the Stockholm tamoxifen (STO)-trials with complete 20-years follow-up. Methods: Secondary analysis of ER-positive/HER2-negative patients with Luminal A or B molecular subtype (n=952) from the STO-trials (1976-1997) randomized to TAM (40 mg) vs no endocrine therapy (control). Gene expression data was generated using custom designed Agilent arrays from FFPE breast cancer tumor tissue and was used to define PAM50 molecular subtypes. The clinically used markers were reannotated in 2014 and 2020. Complete 20-year follow-up was obtained from Swedish high-qualitative registries. The long-term distant recurrence-free interval (DRFI) was assessed by Kaplan-Meier, multivariable Cox proportional hazard regression and time-varying analysis, using flexible parametric modelling. Results: Multivariable analysis showed significantly improved long-term DRFI from TAM vs control for both Luminal A (HR=0.59; 95% CI, 0.44-0.81) and Luminal B (HR=0.67; 95% CI, 0.46-0.99) patients. Time-varying analysis showed that patients with Luminal A subtype significantly benefitted from TAM for 15 years (HR=0.60, 95% CI, 0.39-0.94 at year 15), whereas patients with Luminal B subtype had a significant TAM benefit for 5 years (HR=0.64, 95% CI, 0.42-0.98 at year 5), see Table. Furthermore, a significant long-term TAM benefit for patients with large tumor size (pT&amp;gt;20mm: HR=0.46; 95% CI, 0.25-0.84), tumor grade 1-2 (HR=0.55; 95% CI, 0.40-0.77), lymph node-negative (HR=0.51, 95% CI, 0.34-0.78), PR-positive (HR=0.57, 95% CI, 0.40-0.81) and Ki-67-low tumors (HR=0.55, 95% CI, 0.39-0.77) was seen for Luminal A patients. In Luminal B patients, significantly improved long-term DRFI from TAM vs control was seen for small tumor size (pT≤20mm: HR=0.44; 95% CI, 0.24-0.80), tumor grade 1-2 (HR=0.51; 95% CI, 0.29-0.90), lymph node-negative (HR=0.40, 95% CI, 0.19-0.83), PR-positive (HR=0.59, 95% CI, 0.38-0.93) and Ki-67-low tumors (HR=0.45, 95% CI, 0.25-0.84). Conclusions: This study suggests a 15 years tamoxifen benefit for patients with Luminal A subtype tumors, whereas the benefit for patients with Luminal B tumors is up to five years after diagnosis. Furthermore, our study suggests a long-term tamoxifen benefit for patients with less aggressive tumor characteristics regardless of tumor subtype, except for tumor size in Luminal A patients. ER-positive breast cancer is a heterogeneous disease and long-term follow-up studies in molecular subtypes are essential to understand differences in treatment benefit. Table. Time-varying analysis of long-term tamoxifen therapy benefit by PAM50 molecular subtype. Time-varying analysis of distant recurrence-free interval (DRFI) to assess how tamoxifen benefit varied over the 20 year of follow-up using flexible parametric survival modelling. Patients included in analyses with no missing values. Estimated hazard ratios (HR) at year 5, 10, 15 and 20 for patients with Luminal A or Luminal B molecular subtype tumors randomized to tamoxifen therapy, as compared with patients randomized to no endocrine therapy (control). Adjusted for age, period of primary breast cancer diagnosis, tumor size, tumor grade, lymph node status, PR status, Ki-67 status, chemotherapy, radiotherapy, type of surgery, and menopausal status. *indicates significant findings P&amp;lt;0.05 Citation Format: Huma Dar, Annelie Johansson, Anna Nordenskjöld, Gizeh Perez-Tenorio, Christina Yau, Christopher C. Benz, Laura J. Esserman, Bo Nordenskjöld, Olle Stål, Tommy Fornander, Linda S. Lindström. Long-Term Benefit from Adjuvant Tamoxifen in Luminal A and Luminal B Breast Cancer Patients [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-03-04.

Clinical and molecular features of ATM and BRCA2 mutations in metastatic prostate cancer.

245 Background: Homologous recombination repair (HRR) genes are mutated in about 20% of metastatic prostate cancer (mPC) patients. Of these, ATM and BRCA2 mutations exhibit stark differences in response to PARP inhibitors (PARPi). We aimed to investigate the underlying genomic and molecular features of ATM- and BRCA2-mutated mPC and if these contribute to divergent clinical outcomes or future treatment decisions. Methods: Building upon our prior study, we examined a novel subset of mPC 1066 mPCs after exclusion of microsatellite instable (MSI) tumors to prevent elevation of bystander non-driver BRCA2 mutation. NextGen sequencing of DNA (592-gene and/or whole exome) and RNA (whole transcriptome) from mPCs including bone, lymph nodes, and liver metastases, was performed at Caris Life Sciences (Phoenix, AZ). mPCs were stratified by ATM (n= 91) or BRCA2 (n=102) mutations, as well as HRR-deficiency (HRD) based on mutations in 23 other HRR genes (n = 237), and HRR-proficiency (HRP) based on lack of mutations in any HRR genes (n=636). High tumor mutational burden (TMB-high) was defined as ≥10 mutations/Mb. The differential expression analyses were conducted by Limma. Real-world overall survival (OS) was determined from insurance claims data and Kaplan-Meier estimates were calculated. Results: Mutations in ATM and BRCA2 were associated with worse OS compared to the HRP group (HR 0.4, 0.5; CI 0.305-0.81, 0.339-0.845; P &lt; 0.001). ATM or BRCA2 mutations also predicted worse response to the AR-targeted abiraterone/enzalutamide therapies (HR 0.4, 0.3; CI 0.244-1.003, 0.172 – 0.6; P = 0.047, p &lt; 0.001). ATM-mutated tumors exhibited significantly lower levels of TP53 mutations (11.1% vs 35.1% and 40.8% in BRCA2 and HRP, p &lt; 0.01) and RB1 loss (2.1% vs 15.5% in BRCA2, p &lt; 0.05), and harbored genomic amplification of genes in 11q13 (~10% vs ~1.5% in HRP, p &lt; 0.001), which includes CCND1 and genes in the FGF family. BRCA2-mutated tumors were enriched for amplifications in PDCD1 (PD-1) (3.1% vs 0% in HRP, p &lt; 0.005), and were more frequently TMB-High (7.1% vs 0.63% in HRP, p &lt; 0.001). At the gene expression level, BRCA2-mutated mPC exhibited robust correlations with increased KCNJ3 and decreased ALDH1A3, while ATM mutated tumors exhibited decreased correlation with HES4. BRCA2-mutated mPCs were enriched in cell cycle signaling, a potential indicator of platinum sensitivity (Normalized Enrichment Score &gt; 2, FDR &lt; 0.001) but AMT mutated tumors were not enriched of these profiles . Conclusions: We found that somatic ATM and BRCA2 mutations associated with differential OS outcomes, which may help tailor treatment decisions. At the molecular level, ATM- and BRCA2-mutated tumors exhibited differences in the landscape of co-occurring genomic and transcriptional features. These features unique to ATM or BRCA2 mutations can inform rationale for divergent treatment strategies and should be investigated.

Corrigendum to: Molecular biomarker-defined brain tumors: Epidemiology, validity, and completeness in the United States

Corrigendum to: Molecular biomarker-defined brain tumors: Epidemiology, validity, and completeness in the United States

TMET-32. INTRAOPERATIVE MICRODIALYSIS FOR GLIOMA METABOLIC RECONNAISSANCE AND BIOMARKER DISCOVERY

Abstract Gliomas are genomically heterogeneous tumors that may harness a convergent and therapeutically targetable set of metabolic pathways. At present, the metabolic landscape of in situ human gliomas remains incompletely characterized, hampering translational progress. To that end, we are leveraging the previously untapped potential of high molecular weight microdialysis to determine the global extracellular metabolic profiles of live human gliomas. Under an investigational device exemption, HMW microdialysis (&amp;lt; 100 kDa) was performed at 2.0 μL/min in an initial discovery cohort of five patients in glioma and adjacent brain during neurosurgical resection; a subsequent cohort of five patients was independently analyzed to critically evaluate results from the discovery group. Untargeted metabolomics via ultra-performance liquid chromatography-tandem mass spectrometry revealed over 300 named metabolites and five drugs from only 20 μL of microdialysate, representing a short and feasible 10 minutes of intraoperative collection time. Enrichment analysis of each patient’s tumor vs. brain ranked extracellular metabolome highlighted marked metabolic convergence within the most aggressive regions of molecular diverse tumors (FDR = 0). Pathway analysis revealed significant enrichment for large neutral amino acid pathways, including valine, leucine, and isoleucine biosynthesis (p=1.6E-9) and degradation (p=0.001) and glycine, serine, and threonine metabolism (p=4.7E-5). Notably, this amino acid signature was not as abundantly present in nonenhancing tumor when compared to enhancing tumor (Average tumor/brain: 1.9x vs. 4.3x, respectively), suggesting upregulation of neutral amino acid transporters in enhancing tumor or delivery from plasma into the CNS via a disrupted BBB. Interestingly, guanidinoacetate (GAA) was our most highly conserved and upregulated metabolite (128.9x in tumor vs. brain). Given its co-production with ornithine, the precursor to protumorigenic polyamines, we posit that GAA may serve as a biomarker of increased ODC activity in live human gliomas. In conclusion, intraoperative HMW microdialysis feasibly offers improved opportunities to perform glioma metabolic biomarker and therapeutic discovery.