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Supplementary Figure S1

Supplementary methods and Supplementary figure legends - Tracked Changes

It has been recognized for decades that ERBB signaling is important in prostate cancer, but targeting ERBB receptors as a therapeutic strategy for prostate cancer has been ineffective clinically. However, we show here that membranous HER3 protein is commonly highly expressed in lethal prostate cancer, associating with reduced time to castration resistance (CR) and survival. Multiplex immunofluorescence indicated that the HER3 ligand NRG1 is detectable primarily in tumor-infiltrating myelomonocytic cells in human prostate cancer; this observation was confirmed using single-cell RNA sequencing of human prostate cancer biopsies and murine transgenic prostate cancer models. In castration-resistant prostate cancer (CRPC) patient-derived xenograft organoids with high HER3 expression as well as mouse prostate cancer organoids, recombinant NRG1 enhanced proliferation and survival. Supernatant from murine bone marrow–derived macrophages and myeloid-derived suppressor cells promoted murine prostate cancer organoid growth in vitro, which could be reversed by a neutralizing anti-NRG1 antibody and ERBB inhibition. Targeting HER3, especially with the HER3-directed antibody–drug conjugate U3-1402, exhibited antitumor activity against HER3-expressing prostate cancer. Overall, these data indicate that HER3 is commonly overexpressed in lethal prostate cancer and can be activated by NRG1 secreted by myelomonocytic cells in the tumor microenvironment, supporting HER3-targeted therapeutic strategies for treating HER3-expressing advanced CRPC.Significance:HER3 is an actionable target in prostate cancer, especially with anti-HER3 immunoconjugates, and targeting HER3 warrants clinical evaluation in prospective trials.

Supplementary Figure 3: (A) NSCLC U-1810 cells or diploid fibroblasts WI-38 were treated with DMSO, 1 or 2 (3 microM) for 48 h. Cisplatin (20 microM, 72 h) treated U-1810 cells were used as a positive control for induction of apoptotic morphology. Nuclear morphology of cells was examined after fixation in 4 % paraformaldehyde and staining with DAPI. Pictures showing nuclear morphology (magnification 60x, the scale bar equals 25 microm). Arrows show apoptotic morphology of the cell nuclei. (B) NSCLC U-1810 cells were treated with 3 microM concentration of compound 2 and cleavage of caspase-3, caspase-9 or PARP was examined after 24, 48 and 72 h. β actin was used to visualize equal loading.

Supplementary Materials and Methods and Supplementary Figure Legend

Supplementary Figure 1: Separation of Cribrochalina vasculum crude extract and isolation of compounds 1 and 2. (A) The crude extract (43 g) was separated by reversed phase flash chromatography using a gradient of solvents, from 100 % water through 100 % methanol and then to 100 % ethyl acetate. Fraction 10 was further separated twice on a size exclusion Sephadex LH-20 column using 1:1 mixture of chloroform:methanol as mobile phase. The semi-pure fractions from the second Sephadex LH-20 column (fractions 8-11) were combined and separated on a reversed phase HPLC column (semi-preparative YMC C-8) with a mixture of 40:51:9 acetonitrile:methanol:water as an isocratic mobile phase. Two pure substances, (3S)-icos-4E-en-1-yn-3-ol (1) (tR 41.8 min, 70.1 mg) and (3S)-14-methyldocos-4E-en-1-yn-3-ol (2) (tR 67.0 min, 109 mg) were obtained. (B) HPLC chromatogram of the semi-pure fractions 8-11 from the second Sephadex LH-20 column revealed two substances; (3S)-icos-4E-en-1-yn-3-ol (1) and (3S)-14-methyldocos-4E-en-1-yn-3-ol (2). (C) SMB MS fragmentation of compound 2 showed a loss of 14 mass units for each carbon except for C-14 where a loss of 28 mass units was observed, indicating that the branched methyl substituent is situated on C-14.

Supplementary Figure 2: The cytotoxicity of 1 and 2 was examined in NSCLC U-1810 and normal lung fibroblasts (WI-38) following 24 h and 48 h of continuous exposure using MTT assay. Cell viability is given as % of cell survival as compared to DMSO solvent treated cells. Data shown is the mean of three independent experiments {plus minus}SEM. The IC30, IC50 and IC70 concentrations are given in Supplementary Table S3.

Supplementary Table 3: Compound 1 and compound 2-induced cytotoxicity in NSCLC U-1810 and normal diploid fibroblasts WI-38. Concentrations that induced 30 %, 50 % and 70 % (IC30, IC50 and 70) of cell viability reduction upon treatment with 1 or 2 for 24 h, 48 h or 72 h in NSCLC U-1810 and normal diploid fibroblasts WI-38 are given. The Area under the dose-response curve (AUC) is calculated for each treatment. The data presented is based on calculation from 3 independent biological replicates and the entire growth curves are shown in Supplementary Figure S2.

Supplementary Table 2: NMR data of (3S)-14-methyldocos-4E-en-1-yn-3-ol (2).

Supplementary Table 4: Compound 1 and compound 2 -induced cytotoxicity in tumor and normal cells of different origin. Concentrations that induced 30 %, 50 % and 70 % (IC30, IC50 and IC70) of cell viability reduction in tumor (U-1810, U-1285, H69, H82, A2780, SKOV-3) and normal cells (WI-38, cardiomyocytes, PBMC, BJ-5ta, BEAS-2B, RPE-1) treated for 72 h with compounds 1 or 2 are given. The Area under the dose-response curve (AUC) is calculated for each treatment. The data presented is based on calculation from 3 independent biological replicates and the entire growth curves are shown in Fig. 2C and Fig. 2D.

Supplementary Table 1: NMR data of (3S)-icos-4E-en-1-yn-3-ol (1).

Marine-derived compounds have been explored and considered as possible antitumor agents. In this study, we analyzed extracts of the sponge Cribrochalina vasculum for their ability to inhibit tumor cell proliferation. Screening identified two acetylenic compounds of similar structure that showed strong tumor-specific toxicity in non–small cell lung carcinoma (NSCLC) cells and small-cell lung carcinoma cells, and less prominent toxicity in ovarian carcinoma, while having no effect on normal cells. These acetylenic compounds were found to cause a time-dependent increase in activation of apoptotic signaling involving cleavage of caspase-9, caspase-3, and PARP, as well as apoptotic cell morphology in NSCLC cells, but not in normal fibroblasts. Further analysis demonstrated that these compounds caused conformational change in Bak and Bax, and resulted in loss of mitochondrial potential and cytochrome c release in NSCLC cells. Moreover, a decreased phosphorylation of the growth factor signaling kinases Akt, mTOR, and ERK was evident and an increased phosphorylation of JNK was observed. Thus, these acetylenic compounds hold potential as novel therapeutic agents that should be further explored for NSCLC and other tumor malignancies. Mol Cancer Ther; 13(12); 2941–54. ©2014 AACR.

Supplementary Figure from JMJD6 Is a Druggable Oxygenase That Regulates AR-V7 Expression in Prostate Cancer

Supplementary Table from JMJD6 Is a Druggable Oxygenase That Regulates AR-V7 Expression in Prostate Cancer

Endocrine resistance (EnR) in advanced prostate cancer is fatal. EnR can be mediated by androgen receptor (AR) splice variants, with AR splice variant 7 (AR-V7) arguably the most clinically important variant. In this study, we determined proteins key to generating AR-V7, validated our findings using clinical samples, and studied splicing regulatory mechanisms in prostate cancer models. Triangulation studies identified JMJD6 as a key regulator of AR-V7, as evidenced by its upregulation with in vitro EnR, its downregulation alongside AR-V7 by bromodomain inhibition, and its identification as a top hit of a targeted siRNA screen of spliceosome-related genes. JMJD6 protein levels increased (P < 0.001) with castration resistance and were associated with higher AR-V7 levels and shorter survival (P = 0.048). JMJD6 knockdown reduced prostate cancer cell growth, AR-V7 levels, and recruitment of U2AF65 to AR pre-mRNA. Mutagenesis studies suggested that JMJD6 activity is key to the generation of AR-V7, with the catalytic machinery residing within a druggable pocket. Taken together, these data highlight the relationship between JMJD6 and AR-V7 in advanced prostate cancer and support further evaluation of JMJD6 as a therapeutic target in this disease.Significance:This study identifies JMJD6 as being critical for the generation of AR-V7 in prostate cancer, where it may serve as a tractable target for therapeutic intervention.

Supplementary Figures 1-4 from Differential Expression of S6K2 Dictates Tissue-Specific Requirement for S6K1 in Mediating Aberrant mTORC1 Signaling and Tumorigenesis

B7-H3 is a cell surface immunomodulatory glycoprotein overexpressed in prostate cancers (PCs). Understanding its longitudinal expression at emergence of castration resistance and association with tumour genomics are critical to the development of and patient selection for B7-H3 targeted therapies.To characterise B7-H3 expression in same-patient hormone-sensitive (HSPC) and castration-resistant (CRPC) PC biopsies, associating this with PC genomics, and to evaluate the antitumour activity of an anti-B7-H3 antibody-drug conjugate (ADC) in human CRPC in vitro and in vivo.We performed immunohistochemistry and next-generation sequencing on a cohort of 98 clinically annotated CRPC biopsies, including 72 patients who also had HSPC biopsies for analyses. We analysed two CRPC transcriptome and exome datasets, and PC scRNASeq datasets. PC organoids (patient-derived xenograft [PDX]-derived organoids [PDX-Os]) were derived from PDXs generated from human CRPC biopsies.We evaluated B7-H3 mRNA expression in relation to a panel of 770 immune-related genes, compared B7-H3 protein expression between same-patient HSPC and CRPC biopsies, determined associations with PC genomic alterations, and evaluated the antitumour activity of DS-7300a, a topoisomerase-1 inhibitor payload anti-B7-H3 ADC, in human PC cell lines, organoids (PDX-Os), and xenografts (PDXs) of different histologies, B7-H3 expressions, and genomics.B7-H3 was among the most highly expressed immunomodulatory genes in CRPCs. Most CRPCs (93%) expressed B7-H3, and in patients who developed CRPC, B7-H3 expression was frequently expressed at the time of HSPC diagnosis (97%). Conversion from B7-H3 positive to negative, or vice versa, during progression from HSPC to CRPC was uncommon. CRPC with neuroendocrine features were more likely to be B7-H3 negative (28%) than adenocarcinomas. B7-H3 is overexpressed in tumours with defective DNA repair gene (ATM and BRCA2) alterations and is associated with ERG expression, androgen receptor (AR) expression, and AR activity signature. DS7300a had antitumour activity against B7-H3 expressing human PC models including cell lines, PDX-Os, and PDXs of adenocarcinoma and neuroendocrine histology.The frequent overexpression of B7-H3 in CRPC compared with normal tissue and other B7 family members implicates it as a highly relevant therapeutic target in these diseases. Mechanisms driving differences in B7-H3 expression across genomic subsets warrant investigation for understanding the role of B7-H3 in cancer growth and for the clinical development of B7-H3 targeted therapies.B7-H3, a protein expressed on the surface of the most lethal prostate cancers, in particular those with specific mutations, can be targeted using drugs that bind B7-H3. These findings are relevant for the development of such drugs and for deciding which patients to treat with these new drugs.

It has been recognized for decades that ERBB signaling is important in prostate cancer, but targeting ERBB receptors as a therapeutic strategy for prostate cancer has been ineffective clinically. However, we show here that membranous HER3 protein is commonly highly expressed in lethal prostate cancer, associating with reduced time to castration resistance (CR) and survival. Multiplex immunofluorescence indicated that the HER3 ligand NRG1 is detectable primarily in tumor-infiltrating myelomonocytic cells in human prostate cancer; this observation was confirmed using single-cell RNA sequencing of human prostate cancer biopsies and murine transgenic prostate cancer models. In castration-resistant prostate cancer (CRPC) patient-derived xenograft organoids with high HER3 expression as well as mouse prostate cancer organoids, recombinant NRG1 enhanced proliferation and survival. Supernatant from murine bone marrow–derived macrophages and myeloid-derived suppressor cells promoted murine prostate cancer organoid growth in vitro, which could be reversed by a neutralizing anti-NRG1 antibody and ERBB inhibition. Targeting HER3, especially with the HER3-directed antibody–drug conjugate U3-1402, exhibited antitumor activity against HER3-expressing prostate cancer. Overall, these data indicate that HER3 is commonly overexpressed in lethal prostate cancer and can be activated by NRG1 secreted by myelomonocytic cells in the tumor microenvironment, supporting HER3-targeted therapeutic strategies for treating HER3-expressing advanced CRPC. Significance: HER3 is an actionable target in prostate cancer, especially with anti-HER3 immunoconjugates, and targeting HER3 warrants clinical evaluation in prospective trials.

The authors have requested that this preprint be removed from Research Square.

Background: High neutrophil-to-lymphocyte ratio (NLR) associates with worse overall survival (OS) from prostate cancer (PC) and low response rates to abiraterone and taxane chemotherapy and may reflect systemic inflammatory changes. A direct link between high NLR and intratumoral myeloid infiltration has not been demonstrated to date. We evaluated the relationship between NLR and intratumor immune cell densities in mCRPC biopsies. Design: mCRPC biopsies from 71 patients treated at The Institute of Cancer Research/Royal Marsden Hospital (ICR/RMH, UK) were stained by immunofluorescence for CD11b, CD15, and DAPI and by immunohistochemistry for CD3 to algorithmically quantify PMN-MDSC and T cell densities in the tumor and stromal compartments. NLR (neutrophil count divided by lymphocyte count), ALP, LDH, and albumin were obtained from blood collected contemporaneous with mCRPC biopsies. Clinical data were retrospectively collected. Negative binomial regression determined the association between leucocyte densities and log-transformed NLR. Modified Poisson regression estimated the risk ratio (RR) for the presence of PMN-MDSCs in relation to higher NLR (>3). OS was analysed using Cox regression and Kaplan-Meier. RNAseq data from Stand Up 2 Cancer/Prostate Cancer Foundation (SU2C/PCF, n=159) and RMH cohorts (n=98) were analysed by Spearman’s correlation. Results: NLR positively associated with the density of PMN-MDSCs infiltrating the tumor (p=0.0004) and stromal (p=0.0007) compartments of mCRPC biopsies as determined by Halo࣪ computational modelling. Tumors with high NLR were more likely to be infiltrated by PMN-MDSCs (RR: 1.41; 95% confidence interval [CI]: 1.04-1.92; p=0.03). NLR independently associated with worse OS from the time of mCRPC biopsy after adjusting for LDH, ALP, metastasis at the time of diagnosis, and albumin (HR: 1.71; 95% CI: 1.20-2.46). Patients with low NLR and an absence of tumor-infiltrating PMN-MDSC had longer OS than those with a high NLR, tumor-infiltrating PMN-MDSCs or a combination of both (p=0.015). Whilst there was no association between NLR or PMN-MDSC density and CD3 T cell density, RNAseq analyses of two independent CRPC cohorts showed that MDSC signatures strongly and positively associated with signatures of T cell terminal exhaustion (SU2C/PCF: rs=0.74; p Conclusion: Peripheral blood NLR was positively correlated with prostate tumor-infiltrating PMN-MDSC density supporting the interaction between the circulating myeloid compartment and intratumoral myeloid infiltration in patients with advanced PC. Citation Format: Christina Guo, Jan Rekowski, Mateus Crespo, Bora Gurel, Wei Yuan, Adam Sharp, Rafael Grochot, Khobe Chandran, Semini Sumanasuriya, Ana Ferreira, Andrea Alimonti, Johann S. de Bono. The neutrophil-to-lymphocyte ratio (NLR) reflects intratumor myeloid derived suppressor cell (MDSC) infiltration in metastatic castration-resistant prostate cancers (mCRPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3415.

The microbiota comprises the microorganisms that live in close contact with the host, with mutual benefit for both counterparts. The contribution of the gut microbiota to the emergence of castration-resistant prostate cancer (CRPC) has not yet been addressed. We found that androgen deprivation in mice and humans promotes the expansion of defined commensal microbiota that contributes to the onset of castration resistance in mice. Specifically, the intestinal microbial community in mice and patients with CRPC was enriched for species capable of converting androgen precursors into active androgens. Ablation of the gut microbiota by antibiotic therapy delayed the emergence of castration resistance even in immunodeficient mice. Fecal microbiota transplantation (FMT) from CRPC mice and patients rendered mice harboring prostate cancer resistant to castration. In contrast, tumor growth was controlled by FMT from hormone-sensitive prostate cancer patients and Prevotella stercorea administration. These results reveal that the commensal gut microbiota contributes to endocrine resistance in CRPC by providing an alternative source of androgens.

Endocrine resistance (EnR) in advanced prostate cancer is fatal. EnR can be mediated by androgen receptor (AR) splice variants, with AR splice variant 7 (AR-V7) arguably the most clinically important variant. In this study, we determined proteins key to generating AR-V7, validated our findings using clinical samples, and studied splicing regulatory mechanisms in prostate cancer models. Triangulation studies identified JMJD6 as a key regulator of AR-V7, as evidenced by its upregulation with in vitro EnR, its downregulation alongside AR-V7 by bromodomain inhibition, and its identification as a top hit of a targeted siRNA screen of spliceosome-related genes. JMJD6 protein levels increased (P < 0.001) with castration resistance and were associated with higher AR-V7 levels and shorter survival (P = 0.048). JMJD6 knockdown reduced prostate cancer cell growth, AR-V7 levels, and recruitment of U2AF65 to AR pre-mRNA. Mutagenesis studies suggested that JMJD6 activity is key to the generation of AR-V7, with the catalytic machinery residing within a druggable pocket. Taken together, these data highlight the relationship between JMJD6 and AR-V7 in advanced prostate cancer and support further evaluation of JMJD6 as a therapeutic target in this disease. Significance: This study identifies JMJD6 as being critical for the generation of AR-V7 in prostate cancer, where it may serve as a tractable target for therapeutic intervention.

Driver genes with a mutually exclusive mutation pattern across tumor genomes are thought to have overlapping roles in tumorigenesis. In contrast, we show here that mutually exclusive prostate cancer driver alterations involving the ERG transcription factor and the ubiquitin ligase adaptor SPOP are synthetic sick. At the molecular level, the incompatible cancer pathways are driven by opposing functions in SPOP. ERG upregulates wild type SPOP to dampen androgen receptor (AR) signaling and sustain ERG activity through degradation of the bromodomain histone reader ZMYND11. Conversely, SPOP-mutant tumors stabilize ZMYND11 to repress ERG-function and enable oncogenic androgen receptor signaling. This dichotomy regulates the response to therapeutic interventions in the AR pathway. While mutant SPOP renders tumor cells susceptible to androgen deprivation therapies, ERG promotes sensitivity to high-dose androgen therapy and pharmacological inhibition of wild type SPOP. More generally, these results define a distinct class of antagonistic cancer drivers and a blueprint toward their therapeutic exploitation., Nature Communications, 12, ISSN:2041-1723

Background Cell entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) depends on binding of the viral spike (S) proteins to angiotensin-converting enzyme 2 and on S protein priming by TMPRSS2. Inhibition of TMPRSS2 may work to block or decrease the severity of SARS-CoV-2 infections. Intriguingly, TMPRSS2 is an androgen-regulated gene that is up-regulated in prostate cancer where it supports tumor progression and is involved in a frequent genetic translocation with the ERG gene. First- or second-generation androgen-deprivation therapies (ADTs) decrease the levels of TMPRSS2. Here we put forward the hypothesis that ADTs may protect patients affected by prostate cancer from SARS-CoV-2 infections. Materials and methods We extracted data regarding 9280 patients (4532 males) with laboratory-confirmed SARS-CoV-2 infection from 68 hospitals in Veneto, one of the Italian regions that was most affected by the coronavirus disease 2019 (COVID-19) pandemic. The parameters used for each COVID-19-positive patient were sex, hospitalization, admission to intensive care unit, death, tumor diagnosis, prostate cancer diagnosis, and ADT. Results There were evaluable 9280 SARS-CoV-2-positive patients in Veneto on 1 April 2020. Overall, males developed more severe complications, were more frequently hospitalized, and had a worse clinical outcome than females. Considering only the Veneto male population (2.4 million men), 0.2% and 0.3% of non-cancer and cancer patients, respectively, tested positive for SARS-CoV-2. Comparing the total number of SARS-CoV-2-positive cases, prostate cancer patients receiving ADT had a significantly lower risk of SARS-CoV-2 infection compared with patients who did not receive ADT (OR 4.05; 95% CI 1.55–10.59). A greater difference was found comparing prostate cancer patients receiving ADT with patients with any other type of cancer (OR 4.86; 95% CI 1.88–12.56). Conclusion Our data suggest that cancer patients have an increased risk of SARS-CoV-2 infections compared with non-cancer patients. However, prostate cancer patients receiving ADT appear to be partially protected from SARS-CoV-2 infections.

Oncogene addiction postulates that the survival and growth of certain tumor cells is dependent upon the activity of one oncogene, despite their multiple genetic and epigenetic abnormalities. This phenomenon provides a foundation for molecular targeted therapy and a rationale for oncogene-based stratification. We have previously reported that the Promyelocytic Leukemia protein (PML) is upregulated in triple negative breast cancer (TNBC) and it regulates cancer-initiating cell function, thus suggesting that this protein can be therapeutically targeted in combination with PML-based stratification. However, the effects of PML perturbation on the bulk of tumor cells remained poorly understood. Here we demonstrate that TNBC cells are addicted to the expression of this nuclear protein. PML inhibition led to a remarkable growth arrest combined with features of senescence in vitro and in vivo. Mechanistically, the growth arrest and senescence were associated to a decrease in MYC and PIM1 kinase levels, with the subsequent accumulation of CDKN1B (p27), a trigger of senescence. In line with this notion, we found that PML is associated to the promoter regions of MYC and PIM1, consistent with their direct correlation in breast cancer specimens. Altogether, our results provide a feasible explanation for the functional similarities of MYC, PIM1, and PML in TNBC and encourage further study of PML targeting strategies for the treatment of this breast cancer subtype. Aologies to those whose related publications were not cited due to space limitations. LA, AS, MPu, AA-A, and LV-J were supported by the Basque Government of education. IH was supported by the Program "Juan de la Cierva" from MINECO. FC acknowledges the Proteomics Unit at VHIO is a member ProteoRed, PRB3 (Grant IPT17/0019-ISCIII-SGEFI/ERDF. RB acknowledges projects BFU2017-84653-P, Consolider BFU2014-57703-REDC, and SAF2017-90900-REDT (MINECO/FEDER, EU). The work of VT is founded by Fundacion Vasca de Innovacion e Investigacion Sanitarias, BIOEF (BIO15/CA/052), the AECC J.P. Bizkaia, the Basque Department of Health (2016111109) and the MINECO (RTI2018-097267-B-I00 (MCIU/AEI/FEDER, UE)). AA was supported by ERC consolidator (683136) and Swiss Cancer League (KFS4267-08-2017) grant, Dr. Josef Steiner Foundation, Swiss CardOnco-Grant of Alfred and Annemarie von Sick grant, Helmut Horten Foundation, SNSF (310030_176045) and PCUK (RIA15-ST2-018). NM-M was supported by the Spanish Association Against Cancer (AECC), AECC JP Vizcaya and CIBERONC. The work of A. Carracedo is supported by the Basque Department of Industry, Tourism and Trade (Elkartek) and the department of education (IKERTALDE IT1106-16), the BBVA foundation, the MINECO (SAF2016-79381R (FEDER/EU); Severo Ochoa Excellence Accreditation SEV2016-0644; Excellence Networks SAF2016-81975-REDT), European Training Networks Project (H2020-MSCA-ITN-308 2016 721532), the AECC (IDEAS175CARR, GCTRA18006CARR), La Caixa Foundation (HR17-00094), FERO foundation, the AstraZeneca Oncology prize and the European Research Council (Starting Grant 336343, PoC 754627). CIBERONC was co-funded with FEDER funds and funded by ISCIII.

Prostate cancer is a major cause of cancer morbidity and mortality. Intra-prostatic inflammation is a risk factor for prostate carcinogenesis, with diet, chemical injury and an altered microbiome being causally implicated. Intra-prostatic inflammatory cell recruitment and expansion can ultimately promote DNA double-strand breaks and androgen receptor activation in prostate epithelial cells. The activation of the senescence-associated secretory phenotype fuels further 'inflammatory storms', with free radicals leading to further DNA damage. This drives the overexpression of DNA repair and tumour suppressor genes, rendering these genes susceptible to mutagenic insults, with carcinogenesis accelerated by germline DNA repair gene defects. We provide updates on recent advances in elucidating prostate carcinogenesis and explore novel therapeutic and prevention strategies harnessing these discoveries.

The mechanisms by which prostate cancer shifts from an indolent castration-sensitive phenotype to lethal castration-resistant prostate cancer (CRPC) are poorly understood. Identification of clinically relevant genetic alterations leading to CRPC may reveal potential vulnerabilities for cancer therapy. Here we find that CUB domain-containing protein 1 (CDCP1), a transmembrane protein that acts as a substrate for SRC family kinases (SFKs), is overexpressed in a subset of CRPC. Notably, CDCP1 cooperates with the loss of the tumor suppressor gene PTEN to promote the emergence of metastatic prostate cancer. Mechanistically, we find that androgens suppress CDCP1 expression and that androgen deprivation in combination with loss of PTEN promotes the upregulation of CDCP1 and the subsequent activation of the SRC/MAPK pathway. Moreover, we demonstrate that anti-CDCP1 immunoliposomes (anti–CDCP1 ILs) loaded with chemotherapy suppress prostate cancer growth when administered in combination with enzalutamide. Thus, our study identifies CDCP1 as a powerful driver of prostate cancer progression and uncovers different potential therapeutic strategies for the treatment of metastatic prostate tumors. ISSN:0021-9738 ISSN:1558-8238