Antibody mediated CDCP1 degradation as mode of action for cancer targeted therapy

Distinct inflammation-related proteins associated with T cell immune recovery during chronic HIV-1 infection

Chronic inflammation and T cell dysregulation persist in individuals infected with human immunodeficiency virus type 1 (HIV-1), even after successful antiretroviral treatment. The mechanism involved is not fully understood. Here, we used Olink proteomics to comprehensively analyze the aberrant inflammation-related proteins (IRPs) in chronic HIV-1-infected individuals, including in 24 treatment-naïve individuals, 33 immunological responders, and 38 immunological non-responders. T cell dysfunction was evaluated as T cell exhaustion, activation, and differentiation using flow cytometry. We identified a cluster of IRPs (cluster 7), including CXCL11, CXCL9, TNF, CXCL10, and IL18, which was closely associated with T cell dysregulation during chronic HIV-1 infection. Interestingly, IRPs in cluster 5, including ST1A1, CASP8, SIRT2, AXIN1, STAMBP, CD40, and IL7, were negatively correlated with the HIV-1 reservoir size. We also identified a combination of CDCP1, CXCL11, CST5, SLAMF1, TRANCE, and CD5, which may be useful for distinguishing immunological responders and immunological non-responders. In conclusion, the distinct inflammatory milieu is closely associated with immune restoration of T cells, and our results provide insight into immune dysregulation during chronic HIV-1 infection.

In-depth immune profiling reveals advanced B- and T-cell differentiation to be associated with Th1-driven immune dysregulation in common variable immunodeficiency

Common variable immunodeficiency (CVID) is an inborn error of immunity characterized by low levels of antibodies. In addition to infections, many patients also suffer from T-helper 1-driven immune dysregulation, which is associated with increased mortality. The aim of this study was to perform in-depth characterization of the T and the B cell compartments in a well-defined cohort of patients affected by CVID and correlate the findings to the level of clinical immune dysregulation. We used mass cytometry, targeted proteomics, flow cytometry and functional assays to delineate the immunological phenotype of 15 CVID-affected patients with different levels of immune dysregulation. Unbiased clustering of T cell mass cytometry data correlated with CVID-related immune dysregulation and plasma protein profiles. Expanded CXCR3+ T-bet-expressing B cells correlated with effector memory CD4+ T cell clusters, and increased plasma levels of CXCR3-ligands. Our findings indicate an interplay between B cells and T cells in CVID-related immune dysregulation and provide a better understanding of the underlying pathological mechanisms.

CUB Domain-Containing Protein 1 (CDCP1) is a rational target for the development of imaging tracers and antibody-drug conjugates for cancer detection and therapy

Rationale: An antibody-drug conjugate (ADC) is a targeted therapy consisting of a cytotoxic payload that is linked to an antibody which targets a protein enriched on malignant cells. Multiple ADCs are currently used clinically as anti-cancer agents significantly improving patient survival. Herein, we evaluated the rationale of targeting the cell surface oncoreceptor CUB domain-containing protein 1 (CDCP1) using ADCs and assessed the efficacy of CDCP1-directed ADCs against a range of malignant tumors.

Methods: CDCP1 mRNA expression was evaluated using large transcriptomic datasets of normal/tumor samples for 23 types of cancer and 15 other normal organs, and CDCP1 protein expression was examined in 34 normal tissues, >300 samples from six types of cancer, and in 49 cancer cell lines. A recombinant human/mouse chimeric anti-CDCP1 antibody (ch10D7) was labelled with ⁸⁹Zirconium or monomethyl auristatin E (MMAE) and tested in multiple pre-clinical cancer models including 36 cancer cell lines and three mouse xenograft models.

Results: Analysis of CDCP1 expression indicates elevated CDCP1 expression in the majority of the cancers and restricted expression in normal human tissues. Antibody ch10D7 demonstrates a high affinity and specificity for CDCP1 inducing cell signalling via Src accompanied by rapid internalization of ch10D7/CDCP1 complexes in cancer cells.⁸⁹Zirconium-labelled ch10D7 accumulates in CDCP1 expressing cells enabling detection of pancreatic cancer xenografts in mice by PET imaging. Cytotoxicity of MMAE-labelled ch10D7 against kidney, colorectal, lung, ovarian, pancreatic and prostate cancer cells in vitro, correlates with the level of CDCP1 on the plasma membrane. ch10D7-MMAE displays robust anti-tumor effects against mouse xenograft models of pancreatic, colorectal and ovarian cancer.

Conclusion: CDCP1 directed imaging agents will be useful for selecting cancer patients for personalized treatment with cytotoxin-loaded CDCP1 targeting agents including antibody-drug conjugates.

Targeting a proteolytic neoepitope on CUB domain containing protein 1 (CDCP1) for RAS-driven cancers

Extracellular proteolysis is frequently dysregulated in disease and can generate proteoforms with unique neoepitopes not found in healthy tissue. Here, we demonstrate that Abs that selectively recognize a proteolytic neoepitope on CUB domain containing protein 1 (CDCP1) could enable more effective and safer treatments for solid tumors. CDCP1 is highly overexpressed in RAS-driven cancers, and its ectodomain is cleaved by extracellular proteases. Biochemical, biophysical, and structural characterization revealed that the 2 cleaved fragments of CDCP1 remain tightly associated with minimal proteolysis-induced conformational change. Using differential phage display, we generated recombinant Abs that are exquisitely selective to cleaved CDCP1 with no detectable binding to the uncleaved form. These Abs potently targeted cleaved CDCP1-expressing cancer cells as an Ab-drug conjugate, an Ab-radionuclide conjugate, and a bispecific T cell engager. In a syngeneic pancreatic tumor model, these cleaved-specific Abs showed tumor-specific localization and antitumor activity with superior safety profiles compared with a pan-CDCP1 approach. Targeting proteolytic neoepitopes could provide an orthogonal "AND" gate for improving the therapeutic index.

Identification of CD318, TSPAN8 and CD66c as target candidates for CAR T cell based immunotherapy of pancreatic adenocarcinoma

A major roadblock prohibiting effective cellular immunotherapy of pancreatic ductal adenocarcinoma (PDAC) is the lack of suitable tumor-specific antigens. To address this challenge, here we combine flow cytometry screenings, bioinformatic expression analyses and a cyclic immunofluorescence platform. We identify CLA, CD66c, CD318 and TSPAN8 as target candidates among 371 antigens and generate 32 CARs specific for these molecules. CAR T cell activity is evaluated in vitro based on target cell lysis, T cell activation and cytokine release. Promising constructs are evaluated in vivo. CAR T cells specific for CD66c, CD318 and TSPAN8 demonstrate efficacies ranging from stabilized disease to complete tumor eradication with CD318 followed by TSPAN8 being the most promising candidates for clinical translation based on functionality and predicted safety profiles. This study reveals potential target candidates for CAR T cell based immunotherapy of PDAC together with a functional set of CAR constructs specific for these molecules.

CDCP1 promotes compensatory renal growth by integrating Src and Met signaling

CDCP1 promotes HGF-induced compensatory renal growth by focally and temporally integrating Src and Met-STAT3 signaling in lipid rafts.

Compensatory growth of organs after loss of their mass and/or function is controlled by hepatocyte growth factor (HGF), but the underlying regulatory mechanisms remain elusive. Here, we show that CUB domain-containing protein 1 (CDCP1) promotes HGF-induced compensatory renal growth. Using canine kidney cells as a model of renal tubules, we found that HGF-induced temporal up-regulation of Src activity and its scaffold protein, CDCP1, and that the ablation of CDCP1 robustly abrogated HGF-induced phenotypic changes, such as morphological changes and cell growth/proliferation. Mechanistic analyses revealed that up-regulated CDCP1 recruits Src into lipid rafts to activate STAT3 associated with the HGF receptor Met, and activated STAT3 induces the expression of matrix metalloproteinases and mitogenic factors. After unilateral nephrectomy in mice, the Met-STAT3 signaling is transiently up-regulated in the renal tubules of the remaining kidney, whereas CDCP1 ablation attenuates regenerative signaling and significantly suppresses compensatory growth. These findings demonstrate that CDCP1 plays a crucial role in controlling compensatory renal growth by focally and temporally integrating Src and Met signaling.

The CDCP1 Signaling Hub: A Target for Cancer Detection and Therapeutic Intervention

CUB-domain containing protein 1 (CDCP1) is a type I transmembrane glycoprotein that is upregulated in malignancies of the breast, lung, colorectum, ovary, kidney, liver, pancreas, and hematopoietic system. Here, we discuss CDCP1 as an important hub for oncogenic signaling and its key roles in malignant transformation and summarize approaches focused on exploiting it for cancer diagnosis and therapy. Elevated levels of CDCP1 are associated with progressive disease and markedly poorer survival. Predominantly located on the cell surface, CDCP1 lies at the nexus of key tumorigenic and metastatic signaling cascades, including the SRC/PKCδ, PI3K/AKT, WNT, and RAS/ERK axes, the oxidative pentose phosphate pathway, and fatty acid oxidation, making important functional contributions to cancer cell survival and growth, metastasis, and treatment resistance. These findings have stimulated the development of agents that target CDCP1 for detection and treatment of a range of cancers, and results from preclinical models suggest that these approaches could be efficacious and have manageable toxicity profiles.

CDCP1-targeted nanoparticles encapsulating phase-shift perfluorohexan for molecular US imaging in vitro

BACKGROUND

Molecular targeted contrast-enhanced ultrasound (CEUS) imaging is a potential imaging strategy to improve the diagnostic accuracy of conventional ultrasound (US) imaging. US contrast agents are usually micrometer-sized and non-target gas bubbles while nano-sized and targeted agents containing phase-shift materials absorb more attractions for their size and the liquid core and excellent molecular imaging effect.

METHODS

PLGA12k-mPEG2k-NH2, DSPE-mPEG2k and perfluorohexan (PFH) were used to construct a new targeted ultrasound contrast agent with CUB domain-containing protein 1 (CDCP1) receptor for the detection and diagnosis of prostate cancer. The potential of tumor-targeted nanoparticles (CDCP1-targeted perfluorohexan-loaded phase-transitional nanoparticles, anti-CDCP1 NPs) as contrast agents for ultrasound (US) imaging was assessed in vitro. Moreover, studies on the cytotoxicity and the targeting ability of anti-CDCP1 NPs assisted by US were carried out.

RESULTS

The results showed that anti-CDCP1 NPs had low cytotoxicity, and with the increasing of polymer concentration in anti-CDCP1 NPs, the CEUS imaging of agent gradually enhanced, and enhanced imaging associated with the length of observing time. Furthermore, it was testified that anti-CDCP1 assisted the agent to target cells expressing CDCP1, which demonstrated the active targeting of anti-CDCP1 NPs in vitro.

CONCLUSION

All in all, the feasibility of using targeted anti-CDCP1 NPs to enhance ultrasound imaging has been demonstrated in vitro, which laid a solid foundation for molecular US imaging in vivo, and anti-CDCP1 NPs might have a great clinical application prospect.

Rapid Evaluation of Antibody Fragment Endocytosis for Antibody Fragment-Drug Conjugates

Antibody-drug conjugates (ADCs) have emerged as the most promising strategy in targeted cancer treatment. Recent strategies for the optimization ADCs include the development of antibody fragment-drug conjugates (FDCs). The critical factor in the successful development of ADCs and FDCs is the identification of tumor antigen-specific and internalizing antibodies (Abs). However, systematic comparison or correlation studies of internalization rates with different antibody formats have not been reported previously. In this study, we generated a panel of scFv-phage Abs using phage display technology and their corresponding scFv and scFv-Fc fragments and evaluated their relative internalization kinetics in relation to their antibody forms. We found that the relative rates and levels of internalization of scFv-phage antibodies positively correlate with their scFv and scFv-Fc forms. Our systematic study demonstrates that endocytosis of scFv-phage can serve as a predictive indicator for the assessment of Ab fragment internalization. Additionally, the present study demonstrates that endocytic antibodies can be rapidly screened and selected from phage antibody libraries prior to the conversion of phage antibodies for the generation of the conventional antibody format. Our strategic approach for the identification and evaluation of endocytic antibodies would expedite the selection for optimal antibodies and antibody fragments and be broadly applicable to ADC and FDC development.

CDCP1 overexpression drives prostate cancer progression and can be targeted in vivo

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.

Effective targeting of intact and proteolysed CDCP1 for imaging and treatment of pancreatic ductal adenocarcinoma

Background: CUB domain-containing protein 1 (CDCP1) is a cell surface receptor regulating key signalling pathways in malignant cells. CDCP1 has been proposed as a molecular target to abrogate oncogenic signalling pathways and specifically deliver anti-cancer agents to tumors. However, the development of CDCP1-targeting agents has been questioned by its frequent proteolytic processing which was thought to result in shedding of the CDCP1 extracellular domain limiting its targetability. In this study, we investigated the relevance of targeting CDCP1 in the context of pancreatic ductal adenocarcinoma (PDAC) and assess the impact of CDCP1 proteolysis on the effectiveness of CDCP1 targeting agents. Methods: The involvement of CDCP1 in PDAC progression was assessed by association analysis in several PDAC cohorts and the proteolytic processing of CDCP1 was evaluated in PDAC cell lines and patient-derived cells. The consequences of CDCP1 proteolysis on its targetability in PDAC cells was assessed using immunoprecipitation, immunostaining and biochemical assays. The involvement of CDCP1 in PDAC progression was examined by loss-of-function in vitro and in vivo experiments employing PDAC cells expressing intact or cleaved CDCP1. Finally, we generated antibody-based imaging and therapeutic agents targeting CDCP1 to demonstrate the feasibility of targeting this receptor for detection and treatment of PDAC tumors. Results: High CDCP1 expression in PDAC is significantly associated with poorer patient survival. In PDAC cells proteolysis of CDCP1 does not always result in the shedding of CDCP1-extracellular domain which can interact with membrane-bound CDCP1 allowing signal transduction between the different CDCP1-fragments. Targeting CDCP1 impairs PDAC cell functions and PDAC tumor growth independently of CDCP1 cleavage status. A CDCP1-targeting antibody is highly effective at delivering imaging radionuclides and cytotoxins to PDAC cells allowing specific detection of tumors by PET/CT imaging and superior anti-tumor effects compared to gemcitabine in in vivo models. Conclusion: Independent of its cleavage status, CDCP1 exerts oncogenic functions in PDAC and has significant potential to be targeted for improved radiological staging and treatment of this cancer. Its elevated expression by most PDAC tumors and lack of expression by normal pancreas and other major organs, suggest that targeting CDCP1 could benefit a significant proportion of PDAC patients. These data support the further development of CDCP1-targeting agents as personalizable tools for effective imaging and treatment of PDAC.

Identification of CD318 (CDCP1) as novel prognostic marker in AML

Genetic and morphological markers are well-established prognostic factors in acute myeloid leukemia (AML). However, further reliable markers are urgently needed to improve risk stratification in AML. CD318 (CDCP1) is a transmembrane protein which in solid tumors promotes formation of metastasis and correlates with poor survival. Despite its broad expression on hematological precursor cells, its prognostic significance in hematological malignancies so far remains unclear. Here, we evaluated the role of CD318 as novel prognostic marker in AML by immunophenotyping of leukemic blasts. Flow cytometric evaluation of CD318 on leukemic cells in 70 AML patients revealed a substantial expression in 40/70 (57%) of all cases. CD318 surface levels were significantly correlated with overall survival in patients receiving anthracycline-based induction therapy or best available alternative therapy. Using receiver-operating characteristics, we established a cut-off value to define CD318^lo and CD318^hi expression in both cohorts. Notably, high CD318 expression correlated inversely as prognostic marker in both treatment cohorts: as poor prognostic marker in patients receiving intense therapy, whereas upon palliative care it correlated with better outcome. In conclusion, FACS-based determination of CD318 expression may serve as novel prognostic factor depending on implemented therapy in AML patients.

Anti-CDCP1 immuno-conjugates for detection and inhibition of ovarian cancer

CUB-domain containing protein 1 (CDCP1) is a cancer associated cell surface protein that amplifies pro-tumorigenic signalling by other receptors including EGFR and HER2. Its potential as a cancer target is supported by studies showing that anti-CDCP1 antibodies inhibit cell migration and survival in vitro, and tumor growth and metastasis in vivo. Here we characterize two anti-CDCP1 antibodies, focusing on immuno-conjugates of one of these as a tool to detect and inhibit ovarian cancer. Methods: A panel of ovarian cancer cell lines was examined for cell surface expression of CDCP1 and loss of expression induced by anti-CDCP1 antibodies 10D7 and 41-2 using flow cytometry and Western blot analysis. Surface plasmon resonance analysis and examination of truncation mutants was used to analyse the binding properties of the antibodies for CDCP1. Live-cell spinning-disk confocal microscopy of GFP-tagged CDCP1 was used to track internalization and intracellular trafficking of CDCP1/antibody complexes. In vivo, zirconium 89-labelled 10D7 was detected by positron-emission tomography imaging, of an ovarian cancer patient-derived xenograft grown intraperitoneally in mice. The efficacy of cytotoxin-conjugated 10D7 was examined against ovarian cancer cells in vitro and in vivo. Results: Our data indicate that each antibody binds with high affinity to the extracellular domain of CDCP1 causing rapid internalization of the receptor/antibody complex and degradation of CDCP1 via processes mediated by the kinase Src. Highlighting the potential clinical utility of CDCP1, positron-emission tomography imaging, using zirconium 89-labelled 10D7, was able to detect subcutaneous and intraperitoneal xenograft ovarian cancers in mice, including small (diameter <3 mm) tumor deposits of an ovarian cancer patient-derived xenograft grown intraperitoneally in mice. Furthermore, cytotoxin-conjugated 10D7 was effective at inhibiting growth of CDCP1-expressing ovarian cancer cells in vitro and in vivo. Conclusions: These data demonstrate that CDCP1 internalizing antibodies have potential for killing and detection of CDCP1 expressing ovarian cancer cells.

Sensitization of Tumors for Attack by Virus-Specific CD8+ T-Cells Through Antibody-Mediated Delivery of Immunogenic T-Cell Epitopes

Anti-tumor immunity is limited by a number of factors including the lack of fully activated T-cells, insufficient antigenic stimulation and the immune-suppressive tumor microenvironment. We addressed these hurdles by developing a novel class of immunoconjugates, Antibody-Targeted Pathogen-derived Peptides (ATPPs), which were designed to efficiently deliver viral T-cell epitopes to tumors with the aim of redirecting virus-specific memory T-cells against the tumor. ATPPs were generated through covalent binding of mature MHC class I peptides to antibodies specific for cell surface-expressed tumor antigens that mediate immunoconjugate internalization. By means of a cleavable linker, the peptides are released in the endosomal compartment, from which they are loaded into MHC class I without the need for further processing. Pulsing of tumor cells with ATPPs was found to sensitize these for recognition by virus-specific CD8+ T-cells with much greater efficiency than exogenous loading with free peptides. Systemic injection of ATPPs into tumor-bearing mice enhanced the recruitment of virus-specific T-cells into the tumor and, when combined with immune checkpoint blockade, suppressed tumor growth. Our data thereby demonstrate the potential of ATPPs as a means of kick-starting the immune response against “cold” tumors and increasing the efficacy of checkpoint inhibitors.

A robust six-gene prognostic signature for prediction of both disease-free and overall survival in non-small cell lung cancer

Background

The high mortality of patients with non-small cell lung cancer (NSCLC) emphasizes the necessity of identifying a robust and reliable prognostic signature for NSCLC patients. This study aimed to identify and validate a prognostic signature for the prediction of both disease-free survival (DFS) and overall survival (OS) of NSCLC patients by integrating multiple datasets.

Methods

We firstly downloaded three independent datasets under the accessing number of GSE31210, GSE37745 and GSE50081, and then performed an univariate regression analysis to identify the candidate prognostic genes from each dataset, and identified the gene signature by overlapping the candidates. Then, we built a prognostic model to predict DFS and OS using a risk score method. Kaplan–Meier curve with log-rank test was used to determine the prognostic significance. Univariate and multivariate Cox proportional hazard regression models were implemented to evaluate the influences of various variables on DFS and OS. The robustness of the prognostic gene signature was evaluated by re-sampling tests based on the combined GEO dataset (GSE31210, GSE37745 and GSE50081). Furthermore, a The Cancer Genome Atlas (TCGA)-NSCLC cohort was utilized to validate the prediction power of the gene signature. Finally, the correlation of the risk score of the gene signature and the Gene set variation analysis (GSVA) score of cancer hallmark gene sets was investigated.

Results

We identified and validated a six-gene prognostic signature in this study. This prognostic signature stratified NSCLC patients into the low-risk and high-risk groups. Multivariate regression and stratification analyses demonstrated that the six-gene signature was an independent predictive factor for both DFS and OS when adjusting for other clinical factors. Re-sampling analysis implicated that this six-gene signature for predicting prognosis of NSCLC patients is robust. Moreover, the risk score of the gene signature is correlated with the GSVA score of 7 cancer hallmark gene sets.

Conclusion

This study provided a robust and reliable gene signature that had significant implications in the prediction of both DFS and OS of NSCLC patients, and may provide more effective treatment strategies and personalized therapies.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1899-y) contains supplementary material, which is available to authorized users.

Bagging Nearest-Neighbor Prediction independence Test: an efficient method for nonlinear dependence of two continuous variables

Testing dependence/correlation of two variables is one of the fundamental tasks in statistics. In this work, we proposed an efficient method for nonlinear dependence of two continuous variables (X and Y). We addressed this research question by using BNNPT (Bagging Nearest-Neighbor Prediction independence Test, software available at https://sourceforge.net/projects/bnnpt/). In the BNNPT framework, we first used the value of X to construct a bagging neighborhood structure. We then obtained the out of bag estimator of Y based on the bagging neighborhood structure. The square error was calculated to measure how well Y is predicted by X. Finally, a permutation test was applied to determine the significance of the observed square error. To evaluate the strength of BNNPT compared to seven other methods, we performed extensive simulations to explore the relationship between various methods and compared the false positive rates and statistical power using both simulated and real datasets (Rugao longevity cohort mitochondrial DNA haplogroups and kidney cancer RNA-seq datasets). We concluded that BNNPT is an efficient computational approach to test nonlinear correlation in real world applications.

CD318 is a ligand for CD6

It has been proposed that CD6, an important regulator of T cells, functions by interacting with its currently identified ligand, CD166, but studies performed during the treatment of autoimmune conditions suggest that the CD6-CD166 interaction might not account for important functions of CD6 in autoimmune diseases. The antigen recognized by mAb 3A11 has been proposed as a new CD6 ligand distinct from CD166, yet the identity of it is hitherto unknown. We have identified this CD6 ligand as CD318, a cell surface protein previously found to be present on various epithelial cells and many tumor cells. We found that, like CD6 knockout (KO) mice, CD318 KO mice are also protected in experimental autoimmune encephalomyelitis. In humans, we found that CD318 is highly expressed in synovial tissues and participates in CD6-dependent adhesion of T cells to synovial fibroblasts. In addition, soluble CD318 is chemoattractive to T cells and levels of soluble CD318 are selectively and significantly elevated in the synovial fluid from patients with rheumatoid arthritis and juvenile inflammatory arthritis. These results establish CD318 as a ligand of CD6 and a potential target for the diagnosis and treatment of autoimmune diseases such as multiple sclerosis and inflammatory arthritis.

CDCP1 drives triple-negative breast cancer metastasis through reduction of lipid-droplet abundance and stimulation of fatty acid oxidation

Triple-negative breast cancer (TNBC) is notoriously aggressive with high metastatic potential, which has recently been linked to high rates of fatty acid oxidation (FAO). Here we report the mechanism of lipid metabolism dysregulation in TNBC through the prometastatic protein, CUB-domain containing protein 1 (CDCP1). We show that a "low-lipid" phenotype is characteristic of breast cancer cells compared with normal breast epithelial cells and negatively correlates with invasiveness in 3D culture. Using coherent anti-Stokes Raman scattering and two-photon excited fluorescence microscopy, we show that CDCP1 depletes lipids from cytoplasmic lipid droplets (LDs) through reduced acyl-CoA production and increased lipid utilization in the mitochondria through FAO, fueling oxidative phosphorylation. These findings are supported by CDCP1's interaction with and inhibition of acyl CoA-synthetase ligase (ACSL) activity. Importantly, CDCP1 knockdown increases LD abundance and reduces TNBC 2D migration in vitro, which can be partially rescued by the ACSL inhibitor, Triacsin C. Furthermore, CDCP1 knockdown reduced 3D invasion, which can be rescued by ACSL3 co-knockdown. In vivo, inhibiting CDCP1 activity with an engineered blocking fragment (extracellular portion of cleaved CDCP1) lead to increased LD abundance in primary tumors, decreased metastasis, and increased ACSL activity in two animal models of TNBC. Finally, TNBC lung metastases have lower LD abundance than their corresponding primary tumors, indicating that LD abundance in primary tumor might serve as a prognostic marker for metastatic potential. Our studies have important implications for the development of TNBC therapeutics to specifically block CDCP1-driven FAO and oxidative phosphorylation, which contribute to TNBC migration and metastasis.

Novel small molecule inhibiting CDCP1-PKCδ pathway reduces tumor metastasis and proliferation

CUB domain‐containing protein‐1 (CDCP1) is a trans‐membrane protein predominantly expressed in various cancer cells and involved in tumor progression. CDCP1 is phosphorylated at tyrosine residues in the intracellular domain by Src family kinases and recruits PKCδ to the plasma membrane through tyrosine phosphorylation‐dependent association with the C2 domain of PKCδ, which in turn induces a survival signal in an anchorage‐independent condition. In this study, we used our cell‐free screening system to identify a small compound, glycoconjugated palladium complex (Pd‐Oqn), which significantly inhibited the interaction between the C2 domain of PKCδ and phosphorylated CDCP1. Immunoprecipitation assays demonstrated that Pd‐Oqn hindered the intercellular interaction of phosphorylated CDCP1 with PKCδ and also suppressed the phosphorylation of PKCδ but not that of ERK or AKT. In addition, Pd‐Oqn inhibited the colony formation of gastric adenocarcinoma 44As3 cells in soft agar as well as their invasion. In mouse models, Pd‐Oqn markedly reduced the peritoneal dissemination of gastric adenocarcinoma cells and the tumor growth of pancreatic cancer orthotopic xenografts. These results suggest that the novel compound Pd‐Oqn reduces tumor metastasis and growth by inhibiting the association between CDCP1 and PKCδ, thus potentially representing a promising candidate among therapeutic reagents targeting protein–protein interaction.

miR-198 functions as a tumor suppressor in breast cancer by targeting CUB domain-containing protein 1

The molecular mechanisms underlying the dysregulation of microRNAs (miRs) have been previously documented in breast cancer. miR-198 has been reported to be deregulated in several human cancers. However, the detailed effects of miR-198 on breast cancer progression remain unclear. Using quantitative polymerase chain reaction analysis, we demonstrated in the present study that miR-198 was downregulated in breast cancer tissues and cell lines, and that downregulation of miR-198 was significantly correlated with lymph node metastasis. Functional studies revealed that miR-198 inhibited cell proliferation and migration and promoted cell adhesion in aggressive breast cancer cells in vitro. In addition, we observed that CUB domain-containing protein 1 (CDCP1) was a direct target of miR-198, and that knockdown of CDCP1 inhibited cell proliferation and migration, and promoted cell adhesion, which was similar to the effects of overexpression of miR-198. Taken together, we provide evidence to characterize the role of miR-198/CDCP1 interaction in breast cancer, which may be useful in breast cancer therapy.

CDCP1 cleavage is necessary for homodimerization-induced migration of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly aggressive and metastatic form of breast cancer that lacks the estrogen, progesterone and HER2 receptors and is resistant to targeted and hormone therapies. TNBCs express high levels of the transmembrane glycoprotein, complement C1r/C1s, Uegf, Bmp1 (CUB)-domain containing protein 1 (CDCP1), which has been correlated with the aggressiveness and poor prognosis of multiple carcinomas. Full-length CDCP1 (flCDCP1) can be proteolytically cleaved, resulting in a cleaved membrane-bound isoform (cCDCP1). CDCP1 is phosphorylated by Src family kinases in its full-length and cleaved states, which is important for its pro-metastatic signaling. We observed that cCDCP1, compared with flCDCP1, induced a dramatic increase in phosphorylation of the migration-associated proteins: PKCδ, ERK1/2 and p38 mitogen-activated protein kinase in HEK 293T. In addition, only cCDCP1 induced migration of HEK 293T cells and rescued migration of the TNBC cell lines expressing short hairpin RNA against CDCP1. Importantly, we found that only cCDCP1 is capable of dimerization, which can be blocked by expression of the extracellular portion of cCDCP1 (ECC), indicating that dimerization occurs through CDCP1's ectodomain. We found that ECC inhibited phosphorylation of PKCδ and migration of TNBC cells in two-dimensional culture. Furthermore, ECC decreased cell invasiveness, inhibited proliferation and stimulated apoptosis of TNBC cells in three-dimensional culture, indicating that the cCDCP1 dimer is an important contributor to TNBC aggressiveness. These studies have important implications for the development of a therapeutic to block CDCP1 activity and TNBC metastasis.

Cell line and patient-derived xenograft models reveal elevated CDCP1 as a target in high-grade serous ovarian cancer

BACKGROUND

Development of targeted therapies for high-grade serous ovarian cancer (HGSC) remains challenging, as contributing molecular pathways are poorly defined or expressed heterogeneously. CUB-domain containing protein 1 (CDCP1) is a cell-surface protein elevated in lung, colorectal, pancreas, renal and clear cell ovarian cancer.

METHODS

CUB-domain containing protein 1 was examined by immunohistochemistry in HGSC and fallopian tube. The impact of targeting CDCP1 on cell growth and migration in vitro, and intraperitoneal xenograft growth in mice was examined. Three patient-derived xenograft (PDX) mouse models were developed and characterised for CDCP1 expression. The effect of a monoclonal anti-CDCP1 antibody on PDX growth was examined. Src activation was assessed by western blot analysis.

RESULTS

Elevated CDCP1 was observed in 77% of HGSC cases. Silencing of CDCP1 reduced migration and non-adherent cell growth in vitro and tumour burden in vivo. Expression of CDCP1 in patient samples was maintained in PDX models. Antibody blockade of CDCP1 significantly reduced growth of an HGSC PDX. The CDCP1-mediated activation of Src was observed in cultured cells and mouse xenografts.

CONCLUSIONS

CUB-domain containing protein 1 is over-expressed by the majority of HGSCs. In vitro and mouse model data indicate that CDCP1 has a role in HGSC and that it can be targeted to inhibit progression of this cancer.

New crossroads for potential therapeutic intervention in cancer - intersections between CDCP1, EGFR family members and downstream signaling pathways

Signaling pathways regulated by the receptor CDCP1 play central roles in promoting cancer and in mediating resistance to chemo- and targeted-therapies. In this perspective we briefly summarize these findings as well as data demonstrating poorer outcomes for several malignancies that exhibit elevated CDCP1 expression. Promising data from preclinical studies suggest that CDCP1 targeted agents, including therapeutic antibodies, could be useful in the treatment of cancer patients selected on the basis of activation of CDCP1 and its signaling partners including EGFR, HER2, Met and Src.

Identification of anti-tumour biologics using primary tumour models, 3-D phenotypic screening and image-based multi-parametric profiling

Background

Monolayer cultures of immortalised cell lines are a popular screening tool for novel anti-cancer therapeutics, but these methods can be a poor surrogate for disease states, and there is a need for drug screening platforms which are more predictive of clinical outcome. In this study, we describe a phenotypic antibody screen using three-dimensional cultures of primary cells, and image-based multi-parametric profiling in PC-3 cells, to identify anti-cancer biologics against new therapeutic targets.

Methods

ScFv Antibodies and designed ankyrin repeat proteins (DARPins) were isolated using phage display selections against primary non-small cell lung carcinoma cells. The selected molecules were screened for anti-proliferative and pro-apoptotic activity against primary cells grown in three-dimensional culture, and in an ultra-high content screen on a 3-D cultured cell line using multi-parametric profiling to detect treatment-induced phenotypic changes. The targets of molecules of interest were identified using a cell-surface membrane protein array. An anti-CUB domain containing protein 1 (CDCP1) antibody was tested for tumour growth inhibition in a patient-derived xenograft model, generated from a stage-IV non-small cell lung carcinoma, with and without cisplatin.

Results

Two primary non-small cell lung carcinoma cell models were established for antibody isolation and primary screening in anti-proliferative and apoptosis assays. These assays identified multiple antibodies demonstrating activity in specific culture formats. A subset of the DARPins was profiled in an ultra-high content multi-parametric screen, where 300 morphological features were measured per sample. Machine learning was used to select features to classify treatment responses, then antibodies were characterised based on the phenotypes that they induced. This method co-classified several DARPins that targeted CDCP1 into two sets with different phenotypes. Finally, an anti-CDCP1 antibody significantly enhanced the efficacy of cisplatin in a patient-derived NSCLC xenograft model.

Conclusions

Phenotypic profiling using complex 3-D cell cultures steers hit selection towards more relevant in vivo phenotypes, and may shed light on subtle mechanistic variations in drug candidates, enabling data-driven decisions for oncology target validation. CDCP1 was identified as a potential target for cisplatin combination therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0415-0) contains supplementary material, which is available to authorized users.

Elevated CDCP1 predicts poor patient outcome and mediates ovarian clear cell carcinoma by promoting tumor spheroid formation, cell migration and chemoresistance

Hematogenous metastases are rarely present at diagnosis of ovarian clear cell carcinoma (OCC). Instead dissemination of these tumors is characteristically via direct extension of the primary tumor into nearby organs and the spread of exfoliated tumor cells throughout the peritoneum, initially via the peritoneal fluid, and later via ascites that accumulates as a result of disruption of the lymphatic system. The molecular mechanisms orchestrating these processes are uncertain. In particular, the signaling pathways used by malignant cells to survive the stresses of anchorage-free growth in peritoneal fluid and ascites, and to colonize remote sites, are poorly defined. We demonstrate that the transmembrane glycoprotein CUB-domain-containing protein 1 (CDCP1) has important and inhibitable roles in these processes. In vitro assays indicate that CDCP1 mediates formation and survival of OCC spheroids, as well as cell migration and chemoresistance. Disruption of CDCP1 via silencing and antibody-mediated inhibition markedly reduce the ability of TOV21G OCC cells to form intraperitoneal tumors and induce accumulation of ascites in mice. Mechanistically our data suggest that CDCP1 effects are mediated via a novel mechanism of protein kinase B (Akt) activation. Immunohistochemical analysis also suggested that CDCP1 is functionally important in OCC, with its expression elevated in 90% of 198 OCC tumors and increased CDCP1 expression correlating with poor patient disease-free and overall survival. This analysis also showed that CDCP1 is largely restricted to the surface of malignant cells where it is accessible to therapeutic antibodies. Importantly, antibody-mediated blockade of CDCP1 in vivo significantly increased the anti-tumor efficacy of carboplatin, the chemotherapy most commonly used to treat OCC. In summary, our data indicate that CDCP1 is important in the progression of OCC and that targeting pathways mediated by this protein may be useful for the management of OCC, potentially in combination with chemotherapies and agents targeting the Akt pathway.

Interaction of CDCP1 with HER2 enhances HER2-driven tumorigenesis and promotes trastuzumab resistance in breast cancer

Understanding the molecular pathways that contribute to the aggressive behavior of HER2-positive breast cancers may aid in the development of novel therapeutic interventions. Here, we show that CDCP1 and HER2 are frequently co-overexpressed in metastatic breast tumors and associated with poor patient prognosis. HER2 and CDCP1 co-overexpression leads to increased transformation ability, cell migration, and tumor formation in vivo, and enhanced HER2 activation and downstream signaling in different breast cancer cell lines. Mechanistically, we demonstrate that CDCP1 binds to HER2 through its intracellular domain, thereby increasing HER2 interaction with the non-receptor tyrosine kinase c-SRC (SRC), leading to trastuzumab resistance. Taken together, our findings establish that CDCP1 is a modulator of HER2 signaling and a biomarker for the stratification of breast cancer patients with poor prognosis. Our results also provide a rationale for therapeutic targeting of CDCP1 in HER2-positive breast cancer patients.

The tyrosine phosphatase SHP2 associates with CUB domain-containing protein-1 (CDCP1), regulating its expression at the cell surface in a phosphorylation-dependent manner

CUB domain-containing protein-1 (CDCP1) is a transmembrane glycoprotein that is phosphorylated by SRC family kinases (SFK) before recruiting and activating PKCδ. CDCP1 is overproduced in many cancers. It promotes metastasis and resistance to anoïkis. The robust production of CDCP1 would be associated with stemness and has been proposed as a novel prognosis marker. The natural transmembrane location of CDCP1 makes it an ideal therapeutic target and treatments based on the use of appropriate antibodies are currently being evaluated. However, we still know very little about the molecular fate of CDCP1 and its downstream signaling events. Improvements in our understanding of the molecular events occurring downstream of CDCP1 are required to make use of changes of CDCP1 production or functions for therapeutic purposes. By the mean of co-immunoprecipitation and affinity precipitation we show here, for the first time, that CDCP1 interacts directly, with the cytosolic tyrosine phosphatase SHP2. Point mutants of CDCP1 show that residues Y734 and Y743 are responsible for its interaction with SHP2. It may therefore compete with SFK. We also demonstrate that a shRNA-mediated down regulation of SHP2 is associated with a stronger CDCP1 phosphorylation and an impairment of antibody-mediated CDCP1 internalization.

EGF inhibits constitutive internalization and palmitoylation-dependent degradation of membrane-spanning procancer CDCP1 promoting its availability on the cell surface

Many cancers are dependent on inappropriate activation of epidermal growth factor receptor (EGFR), and drugs targeting this receptor can improve patient survival, although benefits are generally short-lived. We reveal a novel mechanism linking EGFR and the membrane-spanning, cancer-promoting protein CDCP1 (CUB domain-containing protein 1). Under basal conditions, cell surface CDCP1 constitutively internalizes and undergoes palmitoylation-dependent degradation by a mechanism in which it is palmitoylated in at least one of its four cytoplasmic cysteines. This mechanism is functional in vivo as CDCP1 is elevated and palmitoylated in high-grade serous ovarian tumors. Interestingly, activation of the EGFR system with EGF inhibits proteasome-mediated, palmitoylation-dependent degradation of CDCP1, promoting recycling of CDCP1 to the cell surface where it is available to mediate its procancer effects. We also show that mechanisms inducing relocalization of CDCP1 to the cell surface, including disruption of its palmitoylation and EGF treatment, promote cell migration. Our data provide the first evidence that the EGFR system can function to increase the lifespan of a protein and also promote its recycling to the cell surface. This information may be useful for understanding mechanisms of resistance to EGFR therapies and assist in the design of treatments for EGFR-dependent cancers.

Antibody mediated CDCP1 degradation as mode of action for cancer targeted therapy

CUB-domain-containing-protein-1 (CDCP1) is an integral membrane protein whose expression is up-regulated in various cancer types. Although high CDCP1 expression has been correlated with poor prognosis in lung, breast, pancreas, and renal cancer, its functional role in tumor formation or progression is incompletely understood. So far it has remained unclear, whether CDCP1 is a useful target for antibody therapy of cancer and what could be a desired mode of action for a therapeutically useful antibody. To shed light on these questions, we have investigated the cellular effects of a therapeutic antibody candidate (RG7287). In focus formation assays, prolonged RG7287 treatment prevented the loss of contact inhibition caused by co-transformation of NIH3T3 cells with CDCP1 and Src. In a xenograft study, MCF7 cells stably overexpressing CDCP1 reached the predefined tumor volume faster than the parental MCF7 cells lacking endogenous CDCP1. This tumor growth advantage was abolished by RG7287 treatment. In vitro, RG7287 induced rapid tyrosine phosphorylation of CDCP1 by Src, which was accompanied by translocation of CDCP1 to a Triton X-100 insoluble fraction of the plasma membrane. Triggering these effects required bivalency of the antibody suggesting that it involves CDCP1 dimerization or clustering. However, this initial activation of CDCP1 was only transient and prolonged RG7287 treatment induced internalization and down-regulation of CDCP1 in different cancer cell lines. Antibody stimulated CDCP1 degradation required Src activity and was proteasome dependent. Also in three different xenograft models with endogenous CDCP1 expression RG7287 treatment resulted in significant tumor growth inhibition concomitant with substantially reduced CDCP1 levels as judged by immunohistochemistry and Western blotting. Thus, despite transiently activating CDCP1 signaling, the RG7287 antibody has a therapeutically useful mode of action.