Citations

Abstract Background: Cholangiocarcinoma (CCA) is a malignancy of the biliary epithelium with increasing incidence and poor survival. Despite the advances in targeted therapies, treatment success has been hindered by primary or acquired resistance. New therapeutic strategies are necessary to improve outcomes in this patient population. This study investigates the anti-tumor efficacy of TGR-5 inhibition in CCA using a novel small molecular inhibitor, SBI-364. Methods: Cell viability was assessed using a CellTiter-Glo assay in four unique CCA cell lines treated with SBI-364 at concentrations ranging from 1 nM to 100 µM for 48 hours. Viability was expressed as a percentage relative to untreated controls. Cell migration was assessed using a scratch wound healing assay at 0, 12, and 24 hours following SBI-364 treatment. Migration was reported as the percentage of wound closure relative to the initial scratch width. Apoptosis was assessed using the Caspase-Glo® 3/7 Assay (Promega) after 12 hours of treatment with SBI-364. Caspase activity was normalized to untreated controls and expressed as relative luminescence units. Results: SBI-364 reduced cell viability in a dose-dependent manner across all CCA cell lines with IC50 values ranging from 4.1-15.8 µM. Higher concentrations of SBI-364 induced increased cytotoxicity. In the scratch assay, untreated CCA cells achieved 100 % wound closure within 24 hours. Treatment with SBI-364 at 10 µM significantly inhibited cellular migration, with reduced wound closure compared to controls (p < 0.05). Apoptosis analysis revealed a significant increase in caspase-3/7 activity in three CCA cell lines following treatment with 10 µM SBI-364 for 12 hours (p < 0.01). Conclusion: TGR-5 inhibition using novel small molecule inhibitor SBI-364 demonstrates potent anti-tumor effects in CCA by reducing viability, inhibiting migration, and promoting apoptosis. These findings support further investigation of SBI-364 as a promising therapeutic strategy in CCA. Citation Format: Enis Ozmert, Jennifer L. Tomlinson, Danielle M. Carlson, Rory L. Smoot. Efficacy of TGR-5 inhibition in cholangiocarcinoma using the novel small molecule inhibitor SBI-364 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5588.

Abstract Purpose: While an addition of immune checkpoint inhibitor (ICI), pembrolizumab, has improved outcomes of patients with TNBC, early-stage TNBC patients with residual cancer burden (RCB) II/III after neoadjuvant chemotherapy in combination with pembrolizumab (NAP) still have poor outcomes. Previously, we demonstrated that intratumoral HLA-DRA expression and interferon-alpha (IFNα) responses were associated with immune-inflamed phenotype and better outcomes in TNBC patients receiving chemotherapy. This study utilized the CosMx™ SMI to investigate in early-stage TNBC treated with NAP. Methods: Of 151 samples from TNBC patients treated with NAP at Mayo Clinic, 8 pre-treatment biopsy samples (5 pCR and 3 RCB II/III were analyzed using the CosMx™ SMI platform. Linear mixed models to assess differential expression (DE), adjusting for hierarchical data structures. DE analyses were expressed as log2-fold changes (logFC), with the Benjamini-Yekutieli method. GSEA and IPA for signaling pathway exploration. Results: 1.7 million cells were identified across 8 samples after stringent quality control. Immune cell profiling revealed higher B cells, plasma cells, plasmablasts, and T cells (CD4 and CD8) in responders, whereas fibroblasts and myeloid cells were enriched in non-responders. DE analysis showed significantly elevated expression of HLA-DRA (logFC 1.955, p<0.001), other MHC class I and II components, and IFNα in responders. Tumor cells in responders exhibited the highest IFNα expression across cell types. GSEA and IPA analysis revealed enrichment in interferon signaling, antigen presentation, and the cGAS-STING pathway, which drives IFNα production. Spatial analysis categorized cells by their proximity to tumor cells: within 50 µm, 50-100 µm, and over 100 µm. T cells, particularly CD8 T cells, showed a distance-dependent distribution, with a higher abundance near tumor cells in responders. CD8 T cell activation scores declined with increasing distance from IFNα-positive tumor cells but remained consistently low near IFNα-negative tumor cells. IFNγ-positive CD8 T cells exhibited higher activation compared to IFNγ-negative cells, with activation levels influenced by proximity to tumor cells. Lastly, MHC expression in tumor cells was examined relative to CD8 T cell proximity. HLA-DRA and CIITA expression decreased as tumor cells were farther from CD8 T cells. Conclusions: This spatially resolved single-cell analysis highlights the pivotal role of tumor-immune interactions in response to pembrolizumab in TNBC. Our data suggest that tumor cells secrete IFNα through the activation of the cGAS-STING pathway, which activates T cells within close proximity, highlighting the potential role of cGAS-STING agonist as well as IFNα signaling and antigen presentation in augmenting TNBC responses to ICIs. Citation Format: Yi Liu, Saranya Chumsri, Yaohua Ma, Jodi M. Carter, Aziza Nassar, Edith Perez, Roberto A. Leon-Ferre, David Zahrieh, David W. Hillman, Judy C. Boughey, James Ingle, Krishna R. Kalari, Fergus J. Couch, Matthew P. Goetz, Keith L. Knutson, E. Aubrey Thompson. Spatially resolved single-cell analysis reveals cGAS-STING-mediated tumor-immune interactions via IFNα as determinants of pembrolizumab sensitivity in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7130.

Abstract Introduction: Most people who die from prostate cancer are older than 75 years. However, prostate cancer diagnosed at younger ages is often more aggressive. While epidemiologic studies have examined the association between age and survival in patients with prostate cancer overall, the clinical drivers of this relationship in patients with advanced disease remain unclear. We leveraged the International Registry of Men with Advanced Prostate Cancer (IRONMAN, NCT03151629) to (1) quantify the association between age and overall survival and (2) explore whether this association is explained by treatments. Methods: We included 3, 734 patients enrolled from 15 countries with new diagnoses of metastatic hormone sensitive (mHSPC, N=2, 642) or castration resistant prostate cancer (CRPC, N=1, 092). Age at enrollment was categorized as <55, 55-59, 60-64 (reference), 65-69, 70-74, 75-79, 80-84, 85+ years. We computed age-specific death rates (95% confidence intervals [CIs]) by disease state (mHSPC, CRPC) at enrollment. To explore whether this relationship was explained by treatment, we fitted disease state-stratified Cox models and sequentially adjusted for (1) de novo metastatic status and country, and (2) baseline treatment (androgen deprivation therapy [ADT] alone, ADT + androgen receptor pathway inhibitors [ARPI], ADT + chemotherapy, ADT + ARPI + chemotherapy, other). Results: Over 5.5 years of follow-up (median: 3.2 years, IQR: 1.7, 4.8), 995 patients died from any cause. Younger patients were more likely to have de novo metastatic disease. Among those with mHSPC at enrollment, the age-specific death rates per 1, 000 person-years followed a J-shaped pattern: 80 (95% CI: 54, 117) in patients under 55 years, 58 (46, 74) in patients aged 60-64, 102 (78, 133) in patients aged 80-84, and 172 (125, 236) in patients aged 85 and older. The death rates among those with CRPC followed a similar pattern, albeit rates were higher in magnitude: 212 (95% CI: 140, 323) in patients under 55 years, 153 (115, 202) in patients aged 60-64, 200 (155, 258) in patients aged 80-84, and 204 (142, 291) in patients aged 85 and older. After adjusting for disease state, country, and the timing of diagnosis of metastases, death rates were substantially higher for ages 75-79 (HR 1.4; 95% CI 1.1, 1.7), 80-84 years (HR 1.6; 95% CI 1.2, 2.1), and 85 years and older (HR 2.0; 95% CI: 1.5, 2.7) compared to ages 60-64 years. Patients aged under 55 years had 1.4-fold higher death rates (95% CI: 1.0, 1.9) compared to those 60-64 years. After additionally adjusting for baseline treatment, overall survival remained worse for the older patients and the youngest age group with hazard ratios remaining meaningfully unchanged. Conclusion: Age at enrollment is associated with overall survival in people with advanced prostate cancer enrolled in IRONMAN in a J-shaped pattern. This relationship is not explained by differences in baseline treatment. Citation Format: Hannah E. Guard, Michelle O. Sodipo, Colleen B. McGrath, Anna Siefkas, Lauren E. Howard, Konrad H. Stopsack, Christopher M. Sauer, Robert Dreicer, Emilio Esteban, Hassan M. Dogo, Ademola Popoola, Charles Waihenya, Anders Bjartell, Kim N. Chi, Sebastien Hotte, Richard Cathomas, Deborah Enting, Scott Tagawa, Michael Ong, Michael Kolinsky, Vincent Khoo, Joaquin Mateo, Chidiebere N. Ogo, Rana R. McKay, Stefanie Fischer, Heather H. Cheng, Russell Szmulewitz, Young E. Whang, Anand Sharma, Frédéric Pouliot, Simon Crabb, Monica S. Chatwal, Miguel A. Climent, Raymond McDermott, Ian D. Davis, Camille Ragin, Folakemi T. Odedina, Simon Anderson, Simone Badal, Natalie Greaves, Karen A. Autio, Laurel Cannon, Alyssa Chan-Cuzydlo, Marie Grant, Travis Gerke, Hannah D. McManus, Philip W. Kantoff, Daniel J. George, Lorelei A. Mucci, IRONMAN investigator team. Disentangling the association between age and overall survival in an international cohort of patients with advanced prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4935.

Abstract Glioblastoma (GBM), the most aggressive primary brain tumor in adults, presents significant challenges due to its universal recurrence and limited survival rates, exacerbated when proximal to the lateral ventricles (LV). The subpopulation of brain tumor-initiating cells (BTICs) plays a pivotal role in tumor initiation and invasiveness, interacting with the microenvironment, particularly the cellular components in the subventricular zone (SVZ). Some mechanisms of intercellular communication present in the SVZ include paracrine, autocrine, direct cell contact, gap junctions, nanotubes, and more recently extracellular vesicles (EVs). EVs are membrane-bound particles released by cells that are central to intercellular communication. They have the ability to carry bioactive proteins, RNA, and other molecules that influence recipient cell behavior.This study investigates the role of EVs in GBM's communication with non-cancer cells. Our findings indicate that BTIC-derived EVs promote migration and proliferation (*p < 0.02, ****p <0.001) in neural progenitor cells (NPCs) in vitro, highlighting the EVs' role in altering the microenvironment. To identify the protein cargo contained in GBM-derived EVs, we utilized the innovative proximity-labeling system TurboID. We successfully induced TurboID expression in primary-cultured human BTICs from GBM patients, enabling the unbiased biotinylation of proteins in EVs. We isolated biotinylated proteins from BTIC lysates and BTIC-EVs, preserving the integrity of EVs, and conducted proteomic analysis via mass spectrometry. Our method marks the first implementation of TurboID for unbiased global labeling of EV protein cargo in primary GBM cells. This approach facilitates the investigation of EV-mediated communication and potential therapeutic targets, contributing to the understanding of GBM's complex interactions with the brain's microenvironment and the identification of biomarkers for improved diagnosis and treatment response. Citation Format: Marissa Russo, Emily Norton-Ramos, Maria Jose Ulloa Navas, Alfredo Quinones-Hinojosa, Hugo Guerrero-Cazares. Elucidating glioblastoma-derived extracellular vesicle cargo using TurboID: Implications for tumor microenvironment adaptation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6579.

Immunosuppression within the tumor microenvironment (TME) poses a significant challenge to the efficacy of Chimeric Antigen Receptor (CAR) T-cell therapy in solid tumors, including glioblastoma (GBM), the most common and deadly primary brain tumor. Tumor and TME-residing immunosuppressive cells can hijack program death 1(PD1) pathway to evade antitumor T-cell immunity by upregulating its ligand, PD-L1. Thus, targeting PD-L1 emerges as a promising therapeutic strategy to simultaneously eliminate tumor cells and immunosuppressive components within the TME. We developed a novel PD-L1-targeting CAR T-cell therapy, MC9999, and investigated its therapeutic effects against GBM. The antigen-specific cytotoxicity of MC9999 CAR T-cells was firmly validated using a LN229 GBM cell line and its PD-L1-deficient variant, as well as patient-derived brain tumor-initiating cells (BTICs). Furthermore, in vivo therapeutic antitumor effects were confirmed in orthotopic GBM models through intracranial administration of MC9999 CAR T-cells. To pave the way to the translation of MC9999 CAR T-cell therapy to patient bedside, we established a unique experimental system using patient-specific CAR T-cells against their own tumor and immunosuppressive cells. High-quality, patient-specific MC9999 CAR T-cells were manufactured using T cells isolated from peripheral blood, while paired autologous BTICs were generated to serve as target cells. Autologous immunosuppressive cells include monocyte-derived M2 macrophages from patient’s peripheral blood and tumor-associated macrophages (TAMs) isolated from patient’s tumor. Data from multiple patients’ samples consistently demonstrated that these patient-specific MC9999 CAR T-cells elicited robust cytotoxicity against autologous GBM tumor and TME-residing immunosuppressive cells, supporting our hypothesis that targeting PD-L1 effectively address both tumor and its TME. Immunohistochemistry (IHC) staining of our GBM patients’ tissues showed that PD-L1 expression was restricted to tumor cells and macrophages /microglia within the tumor, with no expression detected in neurons, astrocytes, oligodendrocytes, or blood vessels. These findings suggest that MC9999 CAR T-cells can be safely delivered to the brain without compromising normal cell populations. Ongoing studies are underway to further validate the safety profile of MC9999 CAR T-cell therapy. Collectively, the data obtained from this preclinical study support the effectiveness, feasibility and safety of local administration of MC9999 CAR T-cells as a promising new approach for GBM treatment. These encouraging results have motivated us to prepare an Investigational New Drug application to initiate a phase I clinical trial. Citation Format: Yan Luo, Yaqing Qie, Maria J. Ulloa-Navas, Jesus E. Sanchez-Garavito, Vanessa K. Jones, Martha E. Gadd, Mieu M. Brooks, Tanya Hundal, Andrew D. Brim, Isas K. Vazquez-Rosario, Haidong Dong, Alfredo Quinones-Hinojosa, Hong Qin. Intracranial delivery of MC9999 CAR T-cell therapy: a novel strategy to simultaneously eliminate GBM tumors and immunosuppressive components in the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4812.

Abstract Despite the advent of novel targeted therapies with high overall response rates, chronic lymphocytic leukemia (CLL) is still largely incurable due to the development of resistance. The bone marrow microenvironment (BMME) plays an important role in the survival and drug resistance in CLL. BM stromal cells (BMSCs) are considered a key component of BMME. Our long-term goal is to gain further insights of BMSCs-CLL crosstalk influencing both survival and drug resistance in CLL. To understand the global biologic changes that occur in leukemic CLL cells when in contact with BMSCs, we assessed RNA-seq in paired CLL cells isolated from untreated blood and BM and in untreated patients’ CLL cells cultured alone or with BMSCs. CLL cells from blood/BM and cultured alone/with BMSCs were also examined by Immunoprecipitation (IP), Western blot (WB), untargeted metabolomics (LCMS+GCMS), and preclinical drug sensitivity assays. We detected only 13 upregulated genes that overlap between CLL cells from BM and cocultured with BMSCs (p&lt0.05, fold change &gt1.5). When we analyzed the expression of these 13 genes in CLL cells from a cohort of 162 untreated patients by RNA-seq, we found associations between 4 genes (PNP, C16orf54, MOB3A, CDK2AP2) and clinical outcomes including overall survival (OS), progression free survival (PFS), and time to first treatment (TTFT) [multivariable Cox proportional hazards models, p&lt0.05]. Of the 4 genes, purine nucleoside phosphorylase (PNP), an enzyme in the purine pathway, had the most significant association with OS, PFS, and TTFT. Metabolomic profiling indicated an increased level of purine pathway metabolites adenosine, adenine, inosine, and hypoxanthine in cocultured CLL cells. WB analysis showed variable baseline PNP protein expression with 2 cohorts: low /no (L) and high (H) PNP using CLL blood cells. An induction in PNP protein levels were noticed in CLL cells expressing only LPNP when cocultured. Given the association of HPNP with adverse clinical outcomes, we tested for L vs. HPNP cohorts drug sensitivity to known BTK inhibitors(is) or Bcl2is. Treatment of CLL cells from untreated patients with Bcl2is venetoclax, S55746, and LP-118 (Bcl2-Bclxli, Newave) showed increased sensitivity to the Bcl2/Bclxlis in HPNP but not in LPNP cells. In addition, BTKis showed no difference in drug sensitivity associated with CLL PNP levels. To explain this discrepancy, WB and IP analyses were conducted in L vs. HPNP leukemic cells for apoptotic profiles, where we found increased phosphorylated-Bcl2(S70) and an increased association of Bcl2 with Bax in LPNP-expressing CLL cells compared to HPNP. These findings support increased resistance to apoptosis afforded by inhibiting Bcl2 for LPNP vs. HPNP-expressing CLL cells. Our future goals are to continue to understand the prognostic significance of the 4 genes with adverse clinical outcomes and to investigate how best to exploit the peculiar, enhanced sensitivity to Bcl2/Bclxlis found in the HPNP CLL cells. Citation Format: Sutapa Sinha, Weiguo Han, Zhiquan Wang, Brianna M. Finke, Heather C. Darby, Kari G. Rabe, Susan L. Slager, Chantal E. McCabe, Daniel R. O'Brien, Sameer A. Parikh, Esteban Braggio, Yi Chen, Fenlai Tan, Stephen P. Anthony, Yu Chen, Bing Dai, Yue Shen, Neil E. Kay. CLL drug resistance- A multifaceted mechanism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4423.

Abstract Background: Bladder cancer patients with lower socioeconomic status (SES) often present with more aggressive disease and face poor outcomes, likely due to complex interactions with risk factors linked to lower SES. However, little is known about the effect of low SES on bladder tumor biology at the molecular level. This study sought to characterize better the impact of low SES on the bladder tumor microenvironment. Methods: This is a retrospective analysis of 93 patients (63 male and 30 female) ranging from age 33 to 92 presenting to the University of Arizona Cancer Center with bladder cancer from 2016-2023. Each patient's neighborhood level of SES was scored using the Area Deprivation Index on a scale of 1-100, with 1 representing the highest SES and 100 the least. These patients were then split into tertile 1: 1-33 (T1: N=16), tertile 2: 34-67 (T2: N=43), and tertile 3: 68-100 (T3: N=34), and each patient’s tumor microenvironment and mutational landscape was characterized and compared utilizing NGS (592, NextSeq; WES, NovaSeq) and WTS Sequencing (NovaSeq) (Caris Life Sciences, Phoenix, AZ). Statistical significance was determined using chi-square and Mann-Whitney U (p<0.05). Results: Our study had no significant difference between age, sex, and race between the three tertiles. Hispanic ethnicity was significantly higher in T3 (26.5%) when compared to T2 (7%) and T1 (0%), p=0.013. The frequency of TMB-H (>10 mutations/megabase) was significantly lower in T3 (15.6%) when compared to T2 (51.2%, p=0.02) and T1 (50%, p=0.01). There was significantly less T cell CD8+ infiltration in tertile 3 (0.02%) when compared to T2 (0.43%, p=0.04) and T1 (0.37%, p=0.08), and less dendritic cell infiltration in T3 (0%) when compared to T2 (0.1%, p=0.13) and T1 (0.64%, p=0.008). T regulatory cells were lower in T3 (1.37%) compared to T2 (2.13%, p=0.09) and T3 (2.02%, p=0.24). IHC-PD-L1 and gene expression for immune checkpoint genes, MHC-Class I, and MHC-Class II did not vary significantly between tertiles. KMT2C-mt was highest in T2 (21.1%) compared to T1 (3.12%, p=0.03) and T3 (6.67%). There was no other significant differences in mutation prevalence between the three tertiles. Discussion: In our study, lower SES bladder cancer patients had a lower amount of CD8+ cells, dendritic cell infiltration, and a low frequency of TMB-H, indicating a lower level of adaptive immune response present in the tumor microenvironment. Lower levels of adaptive immune activity have been associated with more aggressive tumor behavior and worse outcomes in bladder cancer patients. These findings provide a partial explanation of the molecular mechanisms underlying the poor prognosis observed in low SES patients with bladder cancer. Larger-scale studies exploring the impact of SES on tumor biology are essential as they hold significant therapeutic and preventive implications. Citation Format: Tom Marco, Kenneth Barker, Jesse Ritter, Numaan Mahmood, Rishab Srivastava, Amith Rao, Isaac Zarif, Ricardo Estrada Mendizabal, Sachin Deshmukh, Edgar Tapia, Jose Guillen-Rodriguez, Juan Chipollini, Alejandro Recio-Boiles. The effects of socioeconomic deprivation on the tumor microenvironment of bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7392.

Abstract Introduction: Pseudoangiomatous stromal hyperplasia (PASH) is a benign breast lesion characterized by stromal myofibroblast accumulation. While most women with PASH do not develop breast cancer, a subset eventually does, often in the same breast where PASH was originally diagnosed, even after surgical removal of the lesion. This pattern suggests the presence of a field effect, where alterations in the PASH microenvironment extend beyond the lesion itself, potentially influencing neighboring breast tissue. This study aims to identify specific fibroblasts within PASH-containing tissues that may create a microenvironment conducive to cancer initiation. Methods: We conducted a retrospective analysis of formalin-fixed, paraffin-embedded breast tissue samples from women diagnosed with PASH, comparing those who later developed breast cancer (cases) to those who remained cancer-free (controls). Using transcriptional profiling with NanoString IO360/BC360 panels, multiplex immunofluorescence (MxIF), and spatial transcriptomics via NanoString CosMX SMI, we investigated molecular and histopathological differences. We focused on the expression of fibroblast activation markers (ITGB1, PDGFRβ) and their spatial relationships with proliferating epithelial cells, as well as changes in extracellular matrix (ECM) composition and stiffness. Results: Transcriptional profiling revealed significant upregulation of proliferation-associated genes in epithelial cells from cases. MxIF showed higher Ki-67 levels in epithelial cells from cases, with proliferating cells forming clustered regions. Activated fibroblasts expressing ITGB1 and PDGFRβ were markedly increased in cases and were located closer to proliferating epithelial cells. Spatial transcriptomics uncovered gene expression changes in fibroblasts indicative of an activated phenotype, and in epithelial cells, consistent with responses to increased tissue stiffness and mechanotransduction signaling. Polarized light imaging with picrosirius red staining revealed enhanced collagen cross-linking and thick fibril formation in cases, indicating greater ECM stiffness. Conclusions: Our findings suggest that a subset of activated fibroblasts in benign breast tissue creates a pro-tumorigenic microenvironment through ECM remodeling and increased tissue stiffness, promoting epithelial proliferation and potentially driving cancer development. The spatial proximity of these fibroblasts to proliferating epithelial cells underscores their possible role in early carcinogenesis. This study introduces the novel concept of cancer-predisposing fibroblasts in benign breast tissue, providing new insights into microenvironmental changes that precede cancer and offering potential targets for early detection and intervention. Citation Format: Nicole Cruz-Reyes, Pria Westerman, Matilde Rossi, Camila Pacheco Erak, Melody Stallings Mann, Bryan McCauley, Robert Vierkant, Stacey Winham, Mark Sherman, Amy Degnim, Derek Radisky. Activated fibroblasts in benign breast tissue are associated with subsequent breast cancer development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2083.

Abstract Monoclonal gammopathy of undetermined significance (MGUS) is a precursor to multiple myeloma (MM). Clonal hematopoiesis of indeterminate potential (CHIP) is a precursor to either myeloid or lymphoid malignancy, depending on whether the mutation is in a gene associated with lymphoid (L-CHIP) or myeloid (M-CHIP) outcome. Little is known about the association between CHIP and MGUS and their combined effect on risk of MM. We examined this question within Mayo Clinic Biobank cohort of participants aged 50 years or older with no prior history of hematological malignancies. Using whole blood, individuals were screened for MGUS using a matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry assay. M-CHIP and L-CHIP were defined based on mutations in 56 genes associated with myeloid malignancies or mutations in 235 genes associated with lymphoid malignancies, respectively, using whole-exome-sequencing. Incident MM was identified using International Classification of Diseases (ICD) codes and confirmed via medical record review. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals for the association of CHIP and MGUS. Cox proportional hazards regression was used to estimate hazard ratios (HR), with time defined as date between blood sample and the first incident MM, date of death, or 12/31/2023. All models were adjusted for age and sex. Of the 16, 479 individuals (median age 65 years, 45% male) screened, 12.3% were positive for MGUS, 9.8% were positive for M-CHIP, and 1.5% were positive for L-CHIP. There was no evidence of an association between M-CHIP and MGUS (OR=0.97, 95% CI:0.83-1.12) nor L-CHIP and MGUS (OR=1.12, 95% CI:0.78-1.57), including with any MGUS isotype (IgA, IgG, or IgM; P-values>0.22). Next, we investigated the association of these precursors on risk of MM. Median follow-up was 11.7 years (range 0.1-15.1), and 46 individuals developed incident MM. Both MGUS (HR=29.7, 95% CI: 14.1-62.4) and L-CHIP (HR=4.1, 95% CI: 1.3-13.2) were significantly associated with incident MM, but not M-CHIP (HR-1.0, 95% CI: 0.4-2.5). Investigating the combined effect of MGUS and L-CHIP, we found those with MGUS alone had a 27.5-fold (95% CI: 13.0-58.2) increased risk of incident MM compared to those with no precursors. No individuals with L-CHIP only developed MM, but those with both L-CHIP and MGUS had a 129.4-fold (95% CI: 34.4-486.4) increased risk of incident MM. In the largest cohort with screened MGUS and CHIP, we found no evidence of an association between either definition of CHIP with MGUS. However, individuals with both L-CHIP and MGUS were at the highest risk of developing MM. Citation Format: Nicholas J. Boddicker, Cristine Allmer, Danelle H. Moonen, Aaron D. Norman, Angelica Macauda, Alyssa Clay-Gilmour, Janet E. Olson, Mrinal S. Patnaik, Vincent Rajkumar, Esteban Braggio, David L. Murray, Shaji Kumar, Susan L. Slager, Celine M. Vachon. The association between MGUS and CHIP and their impact on multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4917.