Biology subjects

Haffner, M. C.

Publications and source records attributed to Haffner, M. C..

17 recordsLinked to original sources

bioRxiv2026

Deep learning-based non-invasive profiling of tumor transcriptomes from cell-free DNA for precision oncology

Tumor gene expression profiling provides crucial diagnostic information for guiding therapy, but standard tissue biopsies are invasive, spatially biased, and may inadequately sample metastatic disease. Cell-free DNA (cfDNA) provides a minimally invasive alternative for tumor genotyping, yet reconstructing robust, transcriptome-wide expression from standard-depth cfDNA whole-genome sequencing (WGS) remains a major challenge. We developed a deep learning framework comprising Triton, for comprehensive cfDNA feature extraction, and Proteus, a probabilistic model that infers single-gene expression from standard-depth cfDNA WGS. Proteus outperformed prior cfDNA approaches in reconstructing molecular phenotypes from matched tumor transcriptomes across multiple cancer types, including prostate, lung, and bladder cancer cohorts, with uncertainty-guided withholding improving model reliability. Proteus further enabled assessment of therapeutic target activity, prognostic transcriptional programs, and candidate treatment-emergent resistance states, establishing a generalizable framework for minimally invasive functional genomics in precision oncology.

bioinformatics↗

bioRxiv2025

Armoring STEAP1 CAR T cells with IL-18 potentiates antitumor activity in Ewing sarcoma

BackgroundEwing sarcoma (EwS) is a highly aggressive cancer driven by the EWS::FLI1 fusion oncoprotein affecting children, adolescents, and young adults. Six transmembrane epithelial antigen 1 (STEAP1) is a cell surface antigen transcriptionally controlled by EWS::FLI1 that is broadly expressed in EwS, positioning it as a rational immunotherapy target. However, translating CAR T therapy to solid tumors requires overcoming barriers to potency while maintaining safety. MethodsAnalyses of transcriptome and proteome data were performed to evaluate the effects of EWS::FLI1 perturbation on STEAP1 expression at the transcript and protein levels in EwS models. STEAP1 expression was validated in EwS patient tissues by immunohistochemistry. Second-generation STEAP1-BB{zeta} CAR T cells were tested in orthotopic and disseminated EwS xenograft models. To enhance antitumor activity, an IL-18-armored STEAP1 CAR was engineered. Dose-dependent therapeutic efficacy and safety were evaluated through measurement of tumor burden, survival, and observation for gross toxicities. ResultsSTEAP1 was expressed in [~]97% of primary EwS tumors and directly associated with EWS::FLI1 fusion protein expression in EwS cell lines. In orthotopic EwS models, STEAP1 CAR T cells induced complete tumor regression at 5 x 106 cells. In disseminated disease models, responses were dose-dependent with no evidence of antigen loss. Notably, IL-18 armored STEAP1 CAR T cells achieved complete responses in [~]80% of mice at a reduced dose of 106 cells without overt toxicity. ConclusionsThese data establish STEAP1 as a clinically relevant and highly expressed target in EwS and demonstrate that IL-18 armoring significantly improves CAR T cell efficacy by enhancing potency evident through antitumor activity at reduced cell dose. STEAP1 CAR T cells are currently under evaluation in a first-in-human phase 1/2 dose-escalation clinical trial for metastatic castration-resistant prostate cancer (NCT06236139) and these studies support future clinical translation of STEAP1 CAR T cell therapy for relapsed/refractory EwS.

cancer biology↗

bioRxiv2025

3D pathology-guided microdissection

Traditional micro- and macro-dissection techniques enable the extraction of localized regions in thin tissue sections for molecular analysis. Despite the growing use of 3D microscopy, analogous methods for volumetric microdissection are lacking. We have developed a 3D microdissection method based on computer numerical controlled (CNC) milling integrated with open-top light-sheet microscopy. We demonstrate the ability to study tumor evolution along convoluted 3D branching architectures, which is inaccessible to 2D methods.

bioengineering↗

bioRxiv2025

Defined cellular reprogramming of androgen receptor-active prostate cancer to neuroendocrine prostate cancer

Neuroendocrine prostate cancer (NEPC) arises primarily through neuroendocrine transdifferentiation (NEtD) as an adaptive mechanism of therapeutic resistance. Models to define the functional effects of putative drivers of this process on androgen receptor (AR) signaling and NE cancer lineage programs are lacking. We adapted a genetically defined strategy from the field of cellular reprogramming to directly convert AR-active prostate cancer (ARPC) to AR-independent NEPC using candidate factors. We delineated critical roles of the pioneer factors ASCL1 and NeuroD1 in NEtD and uncovered their abilities to silence AR expression and signaling by remodeling chromatin at the somatically acquired AR enhancer and global AR binding sites with enhancer activity. We also elucidated the dynamic temporal changes in the transcriptomic and epigenomic landscapes of cells undergoing acute lineage conversion from ARPC to NEPC which should inform future therapeutic development. Further, we distinguished the activities of ASCL1 and NeuroD1 from the inactivation of RE-1 silencing transcription factor (REST), a master suppressor of a major neuronal gene program, in establishing a NEPC lineage state and in modulating the expression of genes associated with major histocompatibility complex class I (MHC I) antigen processing and presentation. These findings provide important, clinically relevant insights into the biological processes driving NEtD of prostate cancer.

cancer biology↗

bioRxiv2024

LSD1 inhibition suppresses ASCL1 and de-represses YAP1 to drive potent activity against neuroendocrine prostate cancer

Progression to lethal metastatic castration-resistant prostate cancer (mCRPC) is driven in part by epigenetic modulators such as LSD1 (KDM1A), a lysine-specific demethylase. Yet, mCRPC is increasingly recognized as a highly heterogeneous disease whose classification into subtypes is defined by the extent of androgen receptor (AR) and/or neuroendocrine (NE) characteristics. Meanwhile, the role of LSD1 in driving the different subtypes of mCRPC has remained unclear. Here, we assess the necessity of LSD1 in driving progression of mCRPC subtypes including AR+/NE- (ARPC), AR-/NE+ (NEPC), AR+/NE+ (amphicrine; AMPC), and AR-/NE- (double-negative; DNPC) through the use of LSD1 inhibitors in clinical development. LSD1 inhibition (LSD1i) was observed to be highly effective in restricting growth of NEPC, and efficacy was associated with TP53 loss-of-function. Mice bearing NEPC patient-derived xenografts treated with the LSD1 inhibitors, bomedemstat (MK-3543) or iadademstat (ORY-1001), exhibited suppression of the NE transcriptional profile, including ASCL1. LSD1i also induced expression and activity of YAP1, a non-NE transcription factor canonically silenced in NEPC (YAPOFF cancer), thereby switching NEPC from a YAPOFF to a YAPON cancer class. Therapeutically-induced YAPON NEPC tumors exhibited cell cycle arrest and repression of proliferative transcriptional programs. Importantly, the LSD1i-mediated YAPON state induced sensitivity to an inhibitor of YAP/TEAD function, IAG933, which extended antitumor efficacy against NEPC. Altogether, these findings indicate that patients diagnosed with NEPC may obtain greater relative benefit from LSD1-targeted therapies compared to those with other mCRPC subtypes and that dual inhibition of LSD1 and YAP/TEAD function demonstrates a promising treatment strategy potentially extending to other YAPOFF cancers. SignificanceAcross prostate cancer subtypes, NEPC is exceptionally responsive to LSD1 inhibition and this response is enhanced in combination with a YAP/TEAD disruptor which may improve patient selection and outcomes. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=171 HEIGHT=200 SRC="FIGDIR/small/576106v2_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@77332eorg.highwire.dtl.DTLVardef@1c127d0org.highwire.dtl.DTLVardef@1cec77org.highwire.dtl.DTLVardef@e87ed7_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2023

Combinatorial genetic strategy accelerates the discovery of cancer genotype-phenotype associations

Available genetically-defined cancer models are limited in genotypic and phenotypic complexity and underrepresent the heterogeneity of human cancer. Herein, we describe a combinatorial genetic strategy applied to an organoid transformation assay to rapidly generate diverse, clinically relevant bladder and prostate cancer models. Importantly, the clonal architecture of the resultant tumors can be resolved using single-cell or spatially resolved next-generation sequencing to uncover polygenic drivers of cancer phenotypes.

cancer biology↗

bioRxiv2023

RepairSwitch: simultaneous functional assessment of homologous recombination and end joining DNA repair pathways in living cells

DNA repair pathways are frequently defective in human cancers. DNA double strand breaks (DSBs) are most often repaired by either homologous recombination (HR) or non-homologous end joining (NHEJ). Alterations in repair pathways can indicate sensitivity to therapeutic agents such as PARP inhibitors, cisplatin, and immunotherapy. Thus, functional assays to measure rates of HR and NHEJ are of significant interest. Several methods have been developed to measure rates of HR or NHEJ; however, there is a need for functional cell-based assays that can measure rates by both major DNA DSB pathways simultaneously. Here, we describe the RepairSwitch assay, a flow cytometry assay to assess rates of HR and NHEJ mediated repair of Cas9 programmed DSB simultaneously using a novel fluorescence switching reporter system. The assay exhibits low background signal and is capable of detecting rare repair events in the 1 in 10,000 range. We demonstrate the utility of RepairSwitch by measuring the potency of inhibitors of ATM (KU-60019, KU-55933), DNA-PK (NU7441), and PARP (Olaparib) on modulating DSB repair rates in HEK293FT cells. The selective ATM inhibitor KU-60019 inhibited HR rates with IC50 of 915 nM. Interestingly, KU-60019 exposure led to a dose responsive increase in rates of NHEJ. In contrast, the less selective ATM inhibitor KU-55933, which also has activity on DNA-PK, showed inhibition of both HR and NHEJ. The selective DNA-PK inhibitor NU7441 inhibited NHEJ efficiency with an IC50 of 299 nM, and showed a dose responsive increase in HR. The PARP inhibitor Olaparib showed lower potency in modulating HR and NHEJ. We next used the RepairSwitch assay to assess how pharmacological and genetic inhibition of DNA methyltransferases (DNMT) impacted rates of HR and NHEJ. The DNMT inhibitor decitabine reduced HR, but increased rates of NHEJ, both in a dose responsive manner, in both HEK293FT and HCT116 cells (IC50 for HR of 187 nM and 1.4 uM respectively). Knockout of DNMT1 and DNMT3B increased NHEJ, while knockout of DNMT3B, but not DNMT1, reduced HR. These results illustrate the utility of RepairSwitch as a functional assay for measuring changes in rates of DSB repair induced by pharmacological or genetic perturbation. Furthermore, the findings illustrate the potential for one DNA repair mechanism to compensate in part for loss of another. Finally, we showed that inhibition of DNMT can lead to reduction of HR and increase in NHEJ, providing some additional insight into recently observed synergy of DNMT inhibitors with PARP inhibitors for cancer treatment.

cell biology↗

bioRxiv2022

Nucleosome patterns in circulating tumor DNA reveal transcriptional regulation of advanced prostate cancer phenotypes

Advanced prostate cancers comprise distinct phenotypes, but tumor classification remains clinically challenging. Here, we harnessed circulating tumor DNA (ctDNA) to study tumor phenotypes by ascertaining nucleosome positioning patterns associated with transcription regulation. We sequenced plasma ctDNA whole genomes from patient-derived xenografts representing a spectrum of androgen receptor active (ARPC) and neuroendocrine (NEPC) prostate cancers. Nucleosome patterns associated with transcriptional activity were reflected in ctDNA at regions of genes, promoters, histone modifications, transcription factor binding, and accessible chromatin. We identified the activity of key phenotype-defining transcriptional regulators from ctDNA, including AR, ASCL1, HOXB13, HNF4G, and NR3C1. Using these features, we designed a prediction model which distinguished NEPC from ARPC in patient plasma samples across three clinical cohorts with 97-100% sensitivity and 85-100% specificity. While phenotype classification is typically assessed by immunohistochemistry or transcriptome profiling, we demonstrate that ctDNA provides comparable results with numerous diagnostic advantages for precision oncology. STATEMENT OF SIGNIFICANCEThis study provides key insights into the dynamics of nucleosome positioning and gene regulation associated with cancer phenotypes that can be ascertained from ctDNA. The new methods established for phenotype classification extend the utility of ctDNA beyond assessments of DNA alterations with important implications for molecular diagnostics and precision oncology.

cancer biology↗

bioRxiv2022

Targeting advanced prostate cancer with STEAP1 chimeric antigen receptor T cell therapy

Six transmembrane epithelial antigen of the prostate 1 (STEAP1) is a compelling tumor-associated cell surface antigen for therapeutic targeting in solid tumors. We identified broad expression of STEAP1 (87% positive) in lethal metastatic prostate cancer, even more so than prostate-specific membrane antigen (PSMA, 60% positive) which is a clinically established diagnostic and therapeutic target. Second-generation chimeric antigen receptor (CAR) T cells were engineered for reactivity against STEAP1 and demonstrated substantial antitumor activity in metastatic human prostate cancer models in immunodeficient mice. Adoptive transfer of STEAP1 CAR T cells was associated with prolonged peripheral persistence and either disease eradication or substantial tumor growth inhibition with progressive disease demonstrating antigen loss. As STEAP1 CAR T cells were also highly active in antigen density conditions as low as [~]1,500 molecules/cell, we generated a human STEAP1 (hSTEAP1) knock-in (KI) mouse to evaluate the potential for on-target off-tumor toxicities. hSTEAP1-KI mice demonstrated a pattern of systemic hSTEAP1 expression akin to that observed in humans with the greatest expression found in the prostate gland. Mouse-in-mouse studies of STEAP1 CAR T cell therapy in immunocompetent hSTEAP1-KI mice engrafted with disseminated mouse prostate cancer showed preliminary safety without evidence of gross toxicity, cytokine storm, or architectural disruption and increased T cell infiltration at sites of systemic hSTEAP1 expression. Tumor responses and extension of survival were appreciated but antigen loss was identified in recurrent and progressive disease. In summary, we report the extent of STEAP1 expression in treatment-refractory metastatic prostate cancer, the generation of a STEAP1 CAR T cell therapy with promising potency and safety in preclinical studies of advanced prostate cancer, and antigen escape as a mechanism of resistance to effective STEAP1 CAR T cell therapy.

cancer biology↗

bioRxiv2022

Oncogenic role of a developmentally regulated NTRK2 splice variant

Temporally-regulated alternative splicing choices are vital for proper development yet the wrong splice choice may be detrimental. Here we highlight a novel role for the neurotrophin receptor splice variant TrkB.T1 in neurodevelopment, embryogenesis, transformation, and oncogenesis across multiple tumor types in both humans and mice. TrkB.T1 is the predominant NTRK2 isoform across embryonic organogenesis and forced over-expression of this embryonic pattern causes multiple solid and nonsolid tumors in mice in the context of tumor suppressor loss. TrkB.T1 also emerges the predominant NTRK isoform expressed in a wide range of adult and pediatric tumors, including those harboring TRK fusions. Affinity purification-mass spectrometry (AP-MS) proteomic analysis reveals TrkB.T1 has distinct interactors with known developmental and oncogenic signaling pathways such as Wnt, TGF-{beta}, Hedgehog, and Ras. From alterations in splicing factors to changes in gene expression, the discovery of isoform specific oncogenes with embryonic ancestry has the potential to shape the way we think about developmental systems and oncology.

cancer biology↗

bioRxiv2021

Multilineage plasticity in prostate cancer through expansion of stem-like luminal epithelial cells with elevated inflammatory signaling

Lineage plasticity is a well-established mechanism of resistance to targeted therapies in lung and prostate cancer, where tumors transition from adenocarcinoma to small-cell or neuroendocrine carcinoma. Through single-cell analysis of a cohort of heavily-treated castration-resistant human prostate cancers (CRPC), we report a greater degree of plasticity than previously appreciated, with multiple distinct neuroendocrine (NEPC), mesenchymal (EMT-like), and other subpopulations detected within single biopsies. To explore the steps leading to this plasticity, we turned to two genetically engineered mouse models of prostate cancer that recapitulate progression from adenocarcinoma to neuroendocrine disease. Time course studies reveal expansion of stem-like luminal epithelial cells (Sca1+, Psca+, called L2) that, based on trajectories, gave rise to at least 4 distinct subpopulations, NEPC (Ascl1+), POU2F3 (Pou2f3+), TFF3 (Tff3+) and EMT-like (Vim+, Ncam1+)--these populations are also seen in human prostate and small cell lung cancers. Transformed L2-like cells express stem-like and gastrointestinal endoderm-like transcriptional programs, indicative of reemerging developmental plasticity programs, as well as elevated Jak/Stat and interferon pathway signaling. In sum, while the magnitude of multilineage heterogeneity, both within and across patients, raises considerable treatment challenges, the identification of highly plastic luminal cells as the likely source of this heterogeneity provides a target for more focused therapeutic intervention. One Sentence SummaryMultilineage plasticity results from expansion of stem-like luminal cells with JAK/STAT activation, serving as a therapeutic target.

cancer biology↗

bioRxiv2021

Phased Mutations and Complex Rearrangements in Human Prostate Cancer Cell Lines through Linked-Read Whole Genome Sequencing

A limited number of cell lines have fueled the majority of preclinical Prostate cancer (PCa) research. Despite tremendous effort in characterizing their molecular profiles, comprehensive whole genome sequencing with allelic phasing of somatic genome alterations has not been undertaken to date. Here, we utilized whole genome Linked-read sequencing to obtain haplotype information from the seven most commonly used PCa cell lines (PC3, LNCaP, DU145, CWR22Rv1, VCaP, LAPC4, MDA-PCa-2b), four castrate resistant (CR) subclones (LNCaP_Abl, LNCaP_C42b, VCaP-CR, LAPC4-CR), and an immortalized prostate epithelial line RWPE-1. Phasing of mutations allowed derivation of "Gene-level Haplotype" to assess whether a gene harbored heterozygous mutations in one or both alleles, providing a comprehensive catalogue of mono or bi-allelically inactivated genes. Phased structural variant analysis allowed identification of complex rearrangement chains consistent with chromothripsis and chromoplexy, with breakpoints occurred across a single allele, providing further evidence that complex SVs occurred in a concerted event, rather than through accumulation of multiple independent rearrangements. Additionally, comparison of parental and CR subclones revealed previously known and novel genomic alterations associated with the CR clones. This study therefore comprehensively characterized phased genomic alterations in the commonly used PCa cell lines and provided a useful resource for future cancer research.

cancer biology↗

bioRxiv2021

PHENOTYPIC CHARACTERIZATION OF TWO NOVEL CELL LINE MODELS OF CASTRATION RESISTANT PROSTATE CANCER.

BACKGROUNDResistance to androgen deprivation therapies is a major driver of mortality in advanced prostate cancer. Therefore, there is a need to develop new pre-clinical models that allow the investigation of resistance mechanisms and the assessment of drugs for the treatment of castration resistant prostate cancer. METHODSWe generated two novel cell line models (LAPC4-CR and VCaP-CR) which were derived by passaging LAPC4 and VCaP cells in vivo and in vitro under castrate conditions. We performed detailed transcriptomic (RNA-seq) and proteomic analyses (SWATH-MS) to delineate expression differences between castration-sensitive and castration-resistant cell lines. Furthermore, we characterized the in vivo and in vitro growth characteristics of the novel cell line models. RESULTSThe two cell line derivatives LAPC4-CR and VCaP-CR showed castration resistant growth in vitro and in vivo which was only minimally inhibited by AR antagonists, enzalutamide and bicalutamide. High-dose androgen treatment resulted in significant growth arrest of VCaP-CR but not in LAPC4-CR cells. Both cell lines maintained AR expression, but exhibited distinct expression changes on the mRNA and protein level. Integrated analyses including data from LNCaP and the previously described castration resistant LNCaP-abl cells revealed an expression signature of castration resistance. CONCLUSIONSThe two novel cell line models LAPC4-CR and VCaP-CR and their comprehensive characterization on the RNA and protein level represent important resources to study the molecular mechanisms of castration resistance.

cancer biology↗

bioRxiv2020

Proteogenomic heterogeneity of localized human prostate cancer progression

BackgroundTumor-specific genomic aberrations are routinely determined by high throughput genomic measurements. It remains unclear though, how complex genome alterations affect molecular networks through changing protein levels, and consequently biochemical states of tumor tissues. ResultsHere, we investigated the propagation of genomic effects along the axis of gene expression during prostate cancer progression. For that, we quantified genomic, transcriptomic and proteomic alterations based on 105 prostate samples, consisting of benign prostatic hyperplasia regions and malignant tumors, from 39 prostate cancer patients. Our analysis revealed convergent effects of distinct copy number alterations impacting on common downstream proteins, which are important for establishing the tumor phenotype. We devised a network-based approach that integrates perturbations across different molecular layers, which identified a sub-network consisting of nine genes whose joint activity positively correlated with increasingly aggressive tumor phenotypes and was predictive of recurrence-free survival. Further, our data revealed a wide spectrum of intra-patient network effects, ranging from similar to very distinct alterations on different molecular layers. ConclusionsThis study uncovered molecular networks with remarkably convergent alterations across tumor sites and patients, but it also exposed a diversity of network effects: we could not identify a single sub-network that was perturbed in all high-grade tumor regions.

systems biology↗

bioRxiv2020

Pervasive promoter hypermethylation of silenced TERT alleles in human cancers

In cancers, maintenance of telomeres often occurs through activation of the catalytic subunit of telomerase, encoded by TERT. Yet, most cancers show only modest levels of telomerase gene expression, even in the context of activating hotspot promoter mutations (C228T and C250T). The role of epigenetic mechanisms, including DNA methylation, in regulating telomerase gene expression in cancer cells is not fully understood. Here, we have carried out the most comprehensive characterization to date of TERT promoter methylation using ultra-deep bisulfite sequencing spanning the CpG island surrounding the core TERT promoter in 96 different human cell lines. In general, we observed that immortalized and cancer cell lines were hypermethylated in a region upstream of the recurrent C228T and C250T TERT promoter mutations, while non-malignant primary cells were comparatively hypomethylated in this region. However, at the allele-level, we generally observe hypermethylation of promoter sequences in cancer cells is associated with repressed expression, and the remaining unmethylated alleles marked with open chromatin are largely responsible for the observed TERT expression in cancer cells. Our findings suggest that hypermethylation of the TERT promoter alleles signals transcriptional repression of those alleles, leading to the attenuation of TERT activation in cancer cells. SIGNIFICANCEHypermethylation of the TERT promoter alleles to attenuate TERT activation in cancer cells may account for the modest activation of TERT expression in most cancers.

cancer biology↗

bioRxiv2019

An in situ atlas of mitochondrial DNA in mammalian tissues reveals high content in stem/progenitor cells

Mitochondria regulate ATP production, metabolism and cell death. Alterations in mitochondrial DNA (mtDNA) sequence and copy number are implicated in aging and organ dysfunction in diverse inherited and sporadic diseases. Since most measurements of mtDNA use homogenates of complex tissues, little is known about cell type-specific mtDNA copy number heterogeneity in normal physiology, aging and disease. Thus, the precise cell types whose loss of mitochondrial activity and altered mtDNA copy number that result in organ dysfunction in aging and disease have often not been clarified. Here, we validated an in situ hybridization approach to generate a single cell resolution atlas of mtDNA content in mammalian tissues. In hierarchically organized self-renewing tissues, higher levels of mtDNA were observed in stem/proliferative compartments compared to differentiated compartments. Striking zonal patterns of mtDNA levels in the liver reflected the known oxygen tension gradient. In the kidney, proximal and distal tubules had markedly higher mtDNA levels compared to cells within glomeruli and collecting duct epithelial cells. Decreased mtDNA levels were visualized in renal tubules as a function of aging, which was prevented by calorie restriction. We provide a novel approach for quantifying species- and cell type-specific mtDNA copy number and dynamics in any normal or diseased tissue and can be used for monitoring the effects of interventions in animal and human studies.

pathology↗

bioRxiv2019

Castration-mediated IL-8 Promotes Myeloid Infiltration and Prostate Cancer Progression

Immunotherapy is a treatment for many types of cancer, primarily due to deep and durable clinical responses mediated by immune checkpoint blockade (ICB)1, 2. Prostate cancer is a notable exception in that it is generally unresponsive to ICB. The standard treatment for advanced prostate cancer is androgen-deprivation therapy (ADT), a form of castration (CTX). ADT is initially effective, but over time patients eventually develop castration-resistant prostate cancer (CRPC). Here, we focused on defining tumor-cell intrinsic factors that contribute to prostate cancer progression and resistance to immunotherapy. We analyzed cancer cells isolated from castration-sensitive and castration-resistant prostate tumors, and discovered that castration resulted in significant secretion of Interleukin-8 (IL-8) and its likely murine homolog Cxcl15. These chemokines drove subsequent intra-tumoral infiltration with polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), promoting tumor progression. PMN-MDSC infiltration was abrogated when IL-8 was deleted from prostate cancer epithelial cells using CRISPR/Cas9, or when PMN-MDSC migration was blocked with antibodies against the IL-8 receptor CXCR2. Blocking PMN-MDSC infiltration in combination with anti-CTLA-4 delayed the onset of castration resistance and increased the density of polyfunctional CD8 T cells in tumors. Taken together, our findings establish castration-mediated IL-8 secretion and subsequent PMN-MDSC infiltration as a key suppressive mechanism in the progression of prostate cancer. Targeting of the IL-8/CXCR2 axis around the time of ADT, in combination with ICB, represents a novel therapeutic approach to delay prostate cancer progression to advanced disease.

cancer biology↗