Immune modulator CD70 as a potential cisplatin resistance predictive marker in ovarian cancer

Cell-intrinsic platinum response and associated genetic and gene expression signatures in ovarian cancer cell lines and isogenic models

Ovarian cancers are still largely treated with platinum-based chemotherapy as the standard of care, yet few biomarkers of clinical response have had an impact on clinical decision making as of yet. Two particular challenges faced in mechanistically deciphering platinum responsiveness in ovarian cancer have been the suitability of cell line models for ovarian cancer subtypes and the availability of information on comparatively how sensitive ovarian cancer cell lines are to platinum. We performed one of the most comprehensive profiles to date on 36 ovarian cancer cell lines across over seven subtypes and integrated drug response and multiomic data to improve on our understanding of the best cell line models for platinum responsiveness in ovarian cancer. RNA-seq analysis of the 36 cell lines in a single batch experiment largely conforms with the currently accepted subtyping of ovarian cancers, further supporting other studies that have reclassified cell lines and demonstrate that commonly used cell lines are poor models of high-grade serous ovarian carcinoma. We performed drug dose response assays in the 32 of these cell lines for cisplatin and carboplatin, providing a quantitative database of IC50s for these drugs. Our results demonstrate that cell lines largely fall either well above or below the equivalent dose of the clinical maximally achievable dose (Cmax) of each compound, allowing designation of cell lines as sensitive or resistant. We performed differential expression analysis for high-grade serous ovarian carcinoma cell lines to identify gene expression correlating with platinum-response. Further, we generated two platinum-resistant derivatives each for OVCAR3 and OVCAR4, as well as leveraged clinically-resistant PEO1/PEO4/PEO6 and PEA1/PEA2 isogenic models to perform differential expression analysis for seven total isogenic pairs of platinum resistant cell lines. While gene expression changes overall were heterogeneous and vast, common themes were innate immunity/STAT activation, epithelial to mesenchymal transition and stemness, and platinum influx/efflux regulators. In addition to gene expression analyses, we performed copy number signature analysis and orthogonal measures of homologous recombination deficiency (HRD) scar scores and copy number burden, which is the first report to our knowledge applying field-standard copy number signatures to ovarian cancer cell lines. We also examined markers and functional readouts of stemness that revealed that cell lines are poor models for examination of stemness contributions to platinum resistance, likely pointing to the fact that this is a transient state. Overall this study serves as a resource to determine the best cell lines to utilize for ovarian cancer research on certain subtypes and platinum response studies, as well as sparks new hypotheses for future study in ovarian cancer.

Overview of CD70 as a Potential Therapeutic Target for Osteosarcoma

Osteosarcoma is a primary malignant bone tumor. Effective chemotherapy regimens for refractory disease are scarce, accounting for no improvement in survival. Immune-based cell therapies have emerged as novel alternatives. However, advancements with these therapies have been seen mostly when immune cells are armed to target specific tumor Ags. Recent studies identified cluster of differentiation 70 (CD70) as a promising target to osteosarcoma particularly because CD70 is highly expressed in osteosarcoma lung metastases (Pahl et al. 2015. Cancer Cell Int. 15: 31), and its overexpression by tumors has been correlated with immune evasion and tumor proliferation (Yang et al. 2007. Blood 110: 2537-2544). However, the limited knowledge of the overall CD70 expression within normal tissues and the potential for off-target effect pose several challenges (Flieswasser et al. 2022. J. Exp. Clin. Cancer Res. 41: 12). Nonetheless, CD70-based clinical trials are currently ongoing and are preliminarily showing promising results for patients with osteosarcoma. The present review sheds light on the recent literature on CD70 as it relates to osteosarcoma and highlights the benefits and challenges of targeting this pathway.

Identification of a Novel Immune-Related lncRNA CTD-2288O8.1 Regulating Cisplatin Resistance in Ovarian Cancer Based on Integrated Analysis

Ovarian cancer (OC) is the most lethal gynecological malignancy, in which chemoresistance is a crucial factor leading to the poor prognosis. Recently, immunotherapy has brought new light for the treatment of solid tumors. Hence, as a kind of immunologically active cancer, it is reasonably necessary to explore the potential mechanism between immune characteristics and cisplatin resistance in OC. Our study focused on the important role of cisplatin resistance-related lncRNAs on mediating the OC tumor immune microenvironment (TIME) using an integrative analysis based on the Cancer Genome Atlas (TCGA) database. First, the cisplatin resistance-related differentially expressed lncRNAs (DELs) and mRNAs (DEMs) were preliminarily screened to construct a DEL–DEM co-expression network. Next, the protein–protein interaction (PPI) network and pivot analysis were performed to reveal the relevance of these lncRNAs with tumor immune response. Second, the novel lncRNA CTD-2288O8.1 was identified as a key gene for the OC cisplatin resistance formation by qRT-PCR and survival analysis. Gain- and loss-of-function assays (Cell Counting Kit-8 (CCK-8) assay, wound-healing scratch assay, transwell assay, and colony formation assay) further verified the activity of CTD-2288O8.1 in OC progression as well. Third, gene set enrichment analysis (GSEA) was applied along with the correlation analyses of CTD-2288O8.1 with ImmuneScore, tumor-infiltrating immune cells (TICs), and immune inhibitory checkpoint molecules, illustrating that CTD-2288O8.1 was strongly associated with the TIME and has the potential to predict the effect of OC immunotherapy. In addition, basic experiments demonstrated that the expression of CTD-2288O8.1 impacted the EGFR/AKT signal pathway activity of OC tumor cells. Of greater significance, it promoted the M2 polarization of macrophage, which is a type of the most important components of the TIME in solid tumor. Taking together, our study revealed cisplatin resistance-related lncRNAs closely linked with tumor immunity in OC, underscoring the potential mechanism of the TIME in conferring cisplatin resistance, which provided the research basis for further clinical treatment. CTD-2288O8.1 was identified to mediate cisplatin resistance and affect the response of immunotherapy, which could serve as a promising biomarker for guiding clinical treatment and improving prognosis in OC.

PFKFB3 Regulates Chemoresistance, Metastasis and Stemness via IAP Proteins and the NF-κB Signaling Pathway in Ovarian Cancer

Glycolysis has been reported to be critical for cancer stem cells (CSCs), which are associated with tumor chemoresistance, metastasis and recurrence. Thus, selectively targeting glycolytic enzymes may be a potential therapy for ovarian cancer. 6‐phosphofructo‐2‐kinase/fructose‐2,6‐biphosphatase 3 (PFKFB3), the main source of fructose-2,6-bisphosphate, controls the first committed step in glycolysis. We investigate the clinical significance and roles of PFKFB3 in ovarian cancer using in vitro and in vivo experiments. We demonstrate that PFKFB3 is widely overexpressed in ovarian cancer and correlates with advanced stage/grade and poor outcomes. Significant up-regulation of PFKFB3 was found in ascites and metastatic foci, as well as CSC-enriched tumorspheres and ALDH+CD44+ cells. 3PO, a PFKFB3 inhibitor, reduced lactate level and sensitized A2780CP cells to cisplatin treatment, along with the modulation of inhibitors of apoptosis proteins (c-IAP1, c-IAP2 and survivin) and an immune modulator CD70. Blockade of PFKFB3 by siRNA approach in the CSC-enriched subset led to decreases in glycolysis and CSC properties, and activation of the NF-κB cascade. PFK158, another potent inhibitor of PFKFB3, impaired the stemness of ALDH+CD44+ cells in vitro and in vivo, whereas ectopic expression of PFKFB3 had the opposite results. Overall, PFKFB3 was found to mediate metabolic reprogramming, chemoresistance, metastasis and stemness in ovarian cancer, possibly via the modulation of inhibitors of apoptosis proteins and the NF-κB signaling pathway; thus, suggesting that PFKFB3 may be a potential therapeutic target for ovarian cancer.

Clinical Significance of BTLA, CD27, CD70, CD28 and CD80 as Diagnostic and Prognostic Markers in Ovarian Cancer

It is very important to find new diagnostic and prognostic biomarkers. A total of 79 patients were enrolled in the study. The study group consisted of 37 patients with epithelial ovarian cancer, and the control group consisted of 42 patients with benign ovarian lesions. Five proteins involved in the immune response were studied: BTLA, CD27, CD70, CD28, CD80. The study material was serum and peritoneal fluid. The ROC curve was plotted, and the area under the curve was calculated to characterize the sensitivity and specificity of the studied parameters. Univariate and multivariate analyses were performed simultaneously using the Cox regression model. The cut-off level of CD27 was 120.6 pg/mL, with the sensitivity and specificity of 66 and 84% (p = 0.014). Unfavorable prognostic factors determined in serum were: CD27 (for PFS: HR 1.26, 95% CI 1.21–1.29, p = 0.047; for OS: HR 1.20, 95% CI 1.15–1.22, p = 0.014). Unfavorable prognostic factors determined in peritoneal fluid were: BTLA (for OS: HR 1.26, 95% CI 1.25–1.31, p = 0.033). We conclude that CD27 should be considered as a potential biomarker in the diagnosis of ovarian cancer. BTLA and CD27 are unfavorable prognostic factors for ovarian cancer.

CD70 antibody-drug conjugate: A potential novel therapeutic agent for ovarian cancer

This study aimed to investigate the cytotoxicity of a cluster of differentiation 70 antibody-drug conjugate (CD70-ADC) against ovarian cancer in in vitro and in vivo xenograft models. CD70 expression was assessed in clinical samples by immunohistochemical analysis. Western blotting and fluorescence-activated cell sorting analyses were used to determine CD70 expression in the ovarian cancer cell lines A2780 and SKOV3, and in the cisplatin-resistant ovarian cancer cell lines A2780cisR and SKOV3cisR. CD70 expression after cisplatin exposure was determined in A2780 cells transfected with mock- or nuclear factor (NF)-κB-p65-small interfering RNA. We developed an ADC with an anti-CD70 monoclonal antibody linked to monomethyl auristatin F and investigated its cytotoxic effect. We examined 63 ovarian cancer clinical samples; 43 (68.3%) of them expressed CD70. Among patients with advanced stage disease (n = 50), those who received neoadjuvant chemotherapy were more likely to exhibit high CD70 expression compared to those who did not (55.6% [15/27] vs 17.4% [4/23], P < .01). CD70 expression was confirmed in A2780cisR, SKOV3, and SKOV3cisR cells. Notably, CD70 expression was induced after cisplatin treatment in A2780 mock cells but not in A2780-NF-κB-p65-silenced cells. CD70-ADC was cytotoxic to A2780cisR, SKOV3, and SKOV3cisR cells, with IC₅₀ values ranging from 0.104 to 0.341 nmol/L. In A2780cisR and SKOV3cisR xenograft models, tumor growth in CD70-ADC treated mice was significantly inhibited compared to that in the control-ADC treated mice (A2780cisR: 32.0 vs 1639.0 mm³ , P < .01; SKOV3cisR: 232.2 vs 584.9 mm³ , P < .01). Platinum treatment induced CD70 expression in ovarian cancer cells. CD70-ADC may have potential therapeutic implications in the treatment of CD70 expressing ovarian cancer.

Depleting Tumor Cells Expressing Immune Checkpoint Ligands-A New Approach to Combat Cancer

Antibodies against inhibitory immune checkpoint molecules (ICPMs), referred to as immune checkpoint inhibitors (ICIs), have gained a prominent place in cancer therapy. Several ICIs in clinical use have been engineered to be devoid of effector functions because of the fear that ICIs with preserved effector functions could deplete immune cells, thereby curtailing antitumor immune responses. ICPM ligands (ICPMLs), however, are often overexpressed on a sizeable fraction of tumor cells of many tumor types and these tumor cells display an aggressive phenotype with changes typical of tumor cells undergoing an epithelial-mesenchymal transition. Moreover, immune cells expressing ICPMLs are often endowed with immunosuppressive or immune-deviated functionalities. Taken together, these observations suggest that compounds with the potential of depleting cells expressing ICPMLs may become useful tools for tumor therapy. In this article, we summarize the current state of the art of these compounds, including avelumab, which is the only ICI targeting an ICPML with preserved effector functions that has gained approval so far. We also discuss approaches allowing to obtain compounds with enhanced tumor cell-depleting potential compared to native antibodies. Eventually, we propose treatment protocols that may be applied in order to optimize the therapeutic efficacy of compounds that deplete cells expressing ICPMLs.

Emerging Targets of Immunotherapy in Gynecologic Cancer

Although programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) and cytotoxic T lymphocyte antigen-4 (CTLA-4) have been successfully applied in the treatment of tumors, their efficiency is still not high enough. New immune targets need to be identified in order to seek alternative treatment strategies for patients with refractory tumors. Immune targets can be divided into stimulating and inhibiting molecules according to their function after receptor-ligand binding. We herein present a compendious summary of emerging immune targets in gynecologic tumors. These targets included coinhibitory molecules, such as T cell immunoglobulin-3 (TIM-3), T cell immunoglobulin and ITIM domain (TIGIT), lymphocyte activation gene-3 (LAG-3), V-type immunoglobulin domain-containing suppressor of T cell activation (VISTA), and B7-H3 and B7-H4, and co-stimulatory molecules, such as CD27, OX40, 4-1BB, CD40, glucocorticoid-induced tumor necrosis factor receptor (GITR) and inducible co-stimulator (ICOS). In this review, the characteristics and preclinical/clinical progress of gynecological malignancies are briefly discussed. However, the potential mechanisms and interactions of immune targets need to be elucidated in further studies.

N-Glycome changes reflecting resistance to platinum-based chemotherapy in ovarian cancer

A number of studies have reported aberrant glycosylation in connection with malignancy. Our investigation further expands on this topic through the examination of N-glycans, which could be associated with the resistance of advanced stage, high-grade non-mucinous ovarian cancer to platinum/taxane based chemotherapy. We used tissue samples of 83 ovarian cancer patients, randomly divided into two independent cohorts (basic and validation). Both groups involved either cases with/without postoperative tumor residue or the cases determined either resistant or sensitive to this chemotherapy. In the validation cohort, preoperative serum samples were also available. N-glycans released from tumors and sera were permethylated and analyzed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The MS analysis yielded a consecutive detection of 68 (tissue) and 63 (serum) N-glycan spectral signals. Eight of these were found to be differentially abundant in tissues of both independent cohorts including the cases with a postoperative cancer residue. One of these glycans was detected as differentially abundant in sera of the validation cohort. No statistically significant differences in intensities due to the same N-glycans were found in the cases without postoperative macroscopic residues in either the basic or validation cohort. From the biochemical point of view, the statistically significant N-glycans correspond to the structures carrying bisecting (terminal) GlcNAc residue and tetra-antennary structures with sialic acid and/or fucose residues. Among them, six tissue N-glycans could be considered potential markers connected with a resistance to chemotherapy in ovarian cancer patients. The prediction of primary resistance to standard chemotherapy may identify the group of patients suitable for alternative treatment strategies. SIGNIFICANCE: Drug resistance has become a major impediment to a successful treatment of patients with advanced ovarian cancer. The glycomic measurements related to cancer are becoming increasingly popular in identification of the key molecules as potential diagnostic and prognostic indicators. Our report deals with identification of differences in N-glycosylation of proteins in tissue and serum samples from the individuals showing sensitivity or resistance to platinum/taxane-based chemotherapy. The detection sensitivity to chemotherapy is vitally important for these patients.

In vitro selection of CD70 binding aptamer and its application in a biosensor design for sensitive detection of SKOV-3 ovarian cells

Single-stranded DNA aptamers recognizing CD70 molecule overexpressed in some tumor cell lines was isolated by means of systematic evolution of ligands by exponential enrichment (SELEX). Both purified CD70 protein and CD70-expressing cells were used to isolate target-specific aptamer. After certain rounds of protein-based SELEX and cell-SELEX (ten and seven rounds, respectively), Aptamer 928 (hereafter Apt928) with high affinity and specificity for CD70 was obtained. The specific binding of the aptamer to its target could block interaction of CD70 with CD27 (known as CD70 receptor). Dissociation constant of Apt928 was calculated to be 66 nmol L^-1. Moreover, ATTO 674N-labeled Apt928 was applied as a fluorescent aptasensor for rapid and sensitive detection of SKOV-3 cells as CD70-positive cells. The detection limit of this aptasensor was 14 cells mL^-1.

The expansion of targetable biomarkers for CAR T cell therapy

Biomarkers are an integral part of cancer management due to their use in risk assessment, screening, differential diagnosis, prognosis, prediction of response to treatment, and monitoring progress of disease. Recently, with the advent of Chimeric Antigen Receptor (CAR) T cell therapy, a new category of targetable biomarkers has emerged. These biomarkers are associated with the surface of malignant cells and serve as targets for directing cytotoxic T cells. The first biomarker target used for CAR T cell therapy was CD19, a B cell marker expressed highly on malignant B cells. With the success of CD19, the last decade has shown an explosion of new targetable biomarkers on a range of human malignancies. These surface targets have made it possible to provide directed, specific therapy that reduces healthy tissue destruction and preserves the patient's immune system during treatment. As of May 2018, there are over 100 clinical trials underway that target over 25 different surface biomarkers in almost every human tissue. This expansion has led to not only promising results in terms of patient outcome, but has also led to an exponential growth in the investigation of new biomarkers that could potentially be utilized in CAR T cell therapy for treating patients. In this review, we discuss the biomarkers currently under investigation and point out several promising biomarkers in the preclinical stage of development that may be useful as targets.

Application of chimeric antigen receptor-engineered T cells in ovarian cancer therapy

Due to the critical role of T cells in the immune surveillance of ovarian cancer, adoptive T-cell therapies are receiving increased attention as an immunotherapeutic approach for ovarian cancer. Chimeric antigen receptors (CARs), constructed by incorporating the single-chain Fv fragment to a T-cell signaling domain such as CD3 ζ or Fc receptor γ chain, endow T cell with nonmajor histocompatibility complex-restricted specificity. Dual specificity, trans-signaling CARs and affinity-tuned single-chain Fv fragment have broadened the applicability of CAR-engineered T-cell therapy and may be considered preferential to T cell receptor T-cell therapy in clinical care. As new insights into the CAR-engineered T cells have emerged over the last decade, we review the development of CAR T-cell therapy and discuss the progress and safety concerns regarding its translation from basic research into clinical care of ovarian cancer.

Hypoxia-inducible factor-2 alpha up-regulates CD70 under hypoxia and enhances anchorage-independent growth and aggressiveness in cancer cells

Hypoxia-inducible factors (HIFs) facilitate cellular adaptation to environmental stress such as low oxygen conditions (hypoxia) and consequently promote tumor growth. While HIF-1α functions in cancer progression have been increasingly recognized, the contribution of HIF-2α remains widely unclear despite accumulating reports showing its overexpression in cancer cells. Here, we report that HIF-2α up-regulates the expression of CD70, a cancer-related surface antigen that improves anchorage-independent growth in cancer cells and is associated with poor clinical prognosis, which can be induced via epigenetic modifications mediated by DNMT1. The ablation of CD70 by RNAi led to decreased colony forming efficiency in soft agar. Most strikingly, we identified the emergence of CD70-expressing cells derived from CD70-negative cell lines upon prolonged hypoxia exposure or DNMT1 inhibition, both of which significantly reduced CpG-nucleotide methylations within CD70 promoter region. Interestingly, DNMT1 expression was decreased under hypoxia, which was rescued by HIF-2α knockdown. In addition, the expression of CD70 and colony forming efficiency in soft agar were decreased by knockdown of HIF-2α. These findings indicate that CD70 expression and an aggressive phenotype of cancer cells is driven under hypoxic conditions and mediated by HIF-2α functions and epigenetic modifications. This provides additional insights into the role of HIF-2α in coordinated regulation of stem-like functions and epigenetics that are important for cancer progression and may present additional targets for the development of novel combinatorial therapeutics.

Patient-derived ovarian cancer xenografts re-growing after a cisplatinum treatment are less responsive to a second drug re-challenge: a new experimental setting to study response to therapy

Even if ovarian cancer patients are very responsive to a cisplatinum-based therapy, most will relapse with a resistant disease. New experimental animal models are needed to explore the mechanisms of resistance, to better tailor treatment and improve patient prognosis. To address these aims, seven patient-derived high-grade serous/endometrioid ovarian cancer xenografts were characterized for the antitumor response after one and two cycles of cisplatinum and classified as Very Responsive, Responsive, and Low Responsive to drug treatment. Xenografts re-growing after the first drug cycle were much less responsive to the second one. The expression of epithelial-mesenchymal transition (EMT) and cancer stem cells (CSCs) genes was investigated in cisplatinum-treated and not-treated tumors. We found that different EMT (TCF3, CAMK2N1, EGFR, and IGFBP4) and CSCs (SMO, DLL1, STAT3, and ITGA6) genes were expressed at higher levels in Low Responsive than in Responsive and Very Responsive xenografts. The expression of STAT3 was found to be associated with lower survival (HR = 13.7; p = 0.013) in the TCGA patient data set. MMP9, CD44, DLL4, FOXP1, MERTK, and PTPRC genes were found more expressed in tumors re-growing after cisplatinum treatment than in untreated tumors. We here describe a new in vivo ovarian carcinoma experimental setting that will be instrumental for specific trials of combination therapy to counteract cisplatinum resistance in order to improve the prognosis of ovarian patients.

Tumor cell-associated immune checkpoint molecules - Drivers of malignancy and stemness

Inhibitory or stimulatory immune checkpoint molecules are expressed on a sizeable fraction of tumor cells in different tumor types. It was thought that the main function of tumor cell-associated immune checkpoint molecules would be the modulation (down- or upregulation) of antitumor immune responses. In recent years, however, it has become clear that the expression of immune checkpoint molecules on tumor cells has important consequences on the biology of the tumor cells themselves. In particular, a causal relationship between the expression of these molecules and the acquisition of malignant traits has been demonstrated. Thus, immune checkpoint molecules have been shown to promote the epithelial-mesenchymal transition of tumor cells, the acquisition of tumor-initiating potential and resistance to apoptosis and antitumor drugs, as well as the propensity to disseminate and metastasize. Herein, we review this evidence, with a main focus on PD-L1, the most intensively investigated tumor cell-associated immune checkpoint molecule and for which most information is available. Then, we discuss more concisely other tumor cell-associated immune checkpoint molecules that have also been shown to induce the acquisition of malignant traits, such as PD-1, B7-H3, B7-H4, Tim-3, CD70, CD28, CD137, CD40 and CD47. Open questions in this field as well as some therapeutic approaches that can be derived from this knowledge, are also addressed.

Unlocking the potential of CD70 as a novel immunotherapeutic target for non-small cell lung cancer

Although normally restricted to activated T and B cells and mature dendritic cells, constitutive expression of CD70, a member of the tumor necrosis family, has been described in both hematological and solid tumors, where it increases tumor cell and regulatory T cell survival by signaling through its receptor, CD27.

We have assessed the co-expression of CD70 and CD27 in non-small cell lung cancer (NSCLC) by immunohistochemistry to explore a correlation between expression of the protein and tumor histologic subtype, genetic aberrations and prognosis. Furthermore, we tested the ability of ARGX-110, a CD70-blocking antibody, to induce NK cell-mediated cytotoxicity.

Our results revealed CD70 expression on the surface of both primary and metastatic NSCLC tumor cells and in the tumor microenvironment. Moreover, CD27-expressing tumor infiltrating lymphocytes were found adjacent to the tumor cells, suggesting active CD70-mediated signaling. Finally, we have shown that ARGX-110, has potent cytotoxic effects on CD70⁺ NSCLC cell lines.

T cells and costimulation in cancer

Optimal T cell response is dependent not only on T cell receptor activation, but also on additional signaling from coreceptors. The main coreceptors include B7 and tumor necrosis factor family members. They exert costimulatory or coinhibitory effects, and their balance determines the fate of T cell response. In normal conditions, costimulators facilitate the development of protective immune response, whereas coinhibitors dampen inflammation to avoid organ/tissue damage from excessive immune reaction. In the tumor microenvironment, the balance is garbled: inhibitory pathways predominate, and T cell response is impaired. The importance of cosignaling in the tumor immune response has been experimentally and clinically demonstrated. New therapeutic strategies targeting T cell cosignaling, especially coinhibitory molecules, are under active experimental and clinical investigation. This review summarizes the functions of main T cell cosignaling axes and discusses their clinical application.

Increased CD70 expression is associated with clinical resistance to cisplatin-based chemotherapy and poor survival in advanced ovarian carcinomas

Background

CD70 has been regarded as a novel potential therapeutic target for multiple cancers. In this study, we characterized the expression of the CD70 protein in ovarian carcinomas and assessed its clinical-pathological prognostic value.

Materials and methods

The expression of CD70 in advanced ovarian cancer specimens was assessed by immunohistochemistry. Our results indicated that 16 out of 92 (17.4%) advanced ovarian serous carcinoma tumors showed a high level of CD70 expression. Furthermore, CD70 overexpression was significantly associated with cisplatin-based chemotherapy responses. The high CD70 expression subgroup demonstrated a higher incidence of chemotherapy resistance than the low CD70 subgroup (68.8% versus 25.0%, P = 0.001). Furthermore, univariate analysis conducted on subsets of ovarian carcinoma indicated that high CD70 expression was also associated with decreased survival rates; retained significance was observed on multivariate analysis.

Conclusion

Given the elevated expression of CD70 and its relationship with drug resistance and poor prognosis, our findings suggest that a minor proportion of ovarian carcinomas with CD70 overexpression might be a candidate for the emerging anti-CD70 antibody drug conjugates or therapeutic anti-CD70 antibodies.

Overcoming chemotherapy resistance of ovarian cancer cells by liposomal cisplatin: molecular mechanisms unveiled by gene expression profiling

Previously we reported that liposomal cisplatin (CDDP) overcomes CDDP resistance of ovarian A2780cis cancer cells (Krieger et al., Int. J. Pharm. 389, 2010, 10-17). Here we find that the cytotoxic activity of liposomal CDDP is not associated with detectable DNA platination in resistant ovarian cancer cells. This suggests that the mode of action of liposomal CDDP is different from the free drug. To gain insight into mechanisms of liposomal CDDP activity, we performed a transcriptome analysis of untreated A2780cis cells, and A2780cis cells in response to exposure with IC50 values of free or liposomal CDDP. A process network analysis of upregulated genes showed that liposomal CDDP induced a highly different gene expression profile in comparison to the free drug. p53 was identified as a key player directing transcriptional responses to free or liposomal CDDP. The free drug induced expression of essential genes of the intrinsic (mitochondrial) apoptosis pathway (BAX, BID, CASP9) most likely through p38MAPK activation. In contrast, liposomal CDDP induced expression of genes from DNA damage pathways and several genes of the extrinsic pathway of apoptosis (TNFRSF10B-DR5, CD70-TNFSF7). It thus appears that liposomal CDDP overcomes CDDP resistance by inducing DNA damage and in consequence programmed cell death by the extrinsic pathway. Predictions from gene expression data with respect to apoptosis activation were confirmed at the protein level by an apoptosis antibody array. This sheds new light on liposomal drug carrier approaches in cancer and suggests liposomal CDDP as promising strategy for the treatment of CDDP resistant ovarian carcinomas.

Proteomic identification of paclitaxel-resistance associated hnRNP A2 and GDI 2 proteins in human ovarian cancer cells

Ovarian cancer is a gynecological malignancy with the highest mortality. Chemoresistance is an important subject for the treatment of ovarian cancer, because obtaining significant drug resistance to the first line chemotherapy, paclitaxel, causes major therapeutic obstacles. It is essential to improve the survival rate of ovarian cancer patients by mining the biomarkers indicating the drug resistance and prognosis, and by further understanding underlying mechanisms of drug resistance. In the present study, we established paclitaxel-resistant subline (SKpac) from human epithelial ovarian cancer cell line, SKOV3, and performed comparative analysis of whole proteomes between paclitaxel-resistant SKpac sublines and paclitaxel-sensitive parental SKOV3 cells to identify differentially expressed proteins and useful biomarkers indicating chemoresistance. Proteins related to chemoresistant process were identified by two-dimensional gel electrophoresis (2DE) with mass spectrometry (MALDI-TOF and LC-MS/MS). Eighteen spots were differentially expressed and were identified in SKpac chemoresistant cells compared to SKOV3. The expressions of ALDH 1A1, annexin A1, hnRNP A2, and GDI 2 proteins were validated by Western blot, which was consistent with proteomic analysis. Among the selected proteins, downregulation of hnRNP A2 and GDI 2 was found to be the most significant finding in SKpac cells and chemoresistant ovarian cancer tissues. Our results suggest that hnRNP A2 and GDI 2 may represent potential biomarkers of the paclitaxel-resistant ovarian cancers for tailored cancer therapy.

Targeting pancreatic and ovarian carcinomas using the auristatin-based anti-CD70 antibody-drug conjugate SGN-75

BACKGROUND

CD70 is an ideal target for antibody-based therapies because of its aberrant high expression in renal carcinomas and non-Hodgkin lymphomas and its highly restricted expression in normal tissues. The expression profiling of CD70 in carcinomas has been limited because of the lack of a CD70-specific reagent that works in formalin-fixed paraffin-embedded (FFPE) tissues.

METHODS

We generated murine monoclonal antibodies (mAbs) specific for CD70 and validated their specificity by western blot analysis and developed a protocol for immunohistochemistry on FFPE tissues. CD70+ tumour cell lines were used for testing the anti-tumour activity of the anti-CD70 antibody-drug conjugate, SGN-75.

RESULTS

We report novel detection of CD70 expression in multiple cancers including pancreatic (25%), larynx/pharynx (22%), melanoma (16%), ovarian (15%), lung (10%), and colon (9%). Our results show that pancreatic and ovarian tumour cell lines, which express high levels of endogenous or transfected CD70, are sensitive to the anti-tumour activity of SGN-75 in vitro and in vivo.

CONCLUSION

Development of murine mAbs for robust and extensive screening of FFPE samples coupled with the detection of anti-tumour activity in novel indications provide rationale for expanding the application of SGN-75 for the treatment of multiple CD70 expressing cancers.