Functional genomics identifies ABCC3 as a mediator of taxane resistance in HER2-amplified breast cancer

Lau AT, Xu YM. The regulation of microRNAs on chemoresistance in triple-negative breast cancer: a recent update

Triple-negative breast cancer (TNBC) has negative expressions of ER, PR and HER2. Due to the insensitivity to both endocrine therapy and HER2-targeted therapy, the main treatment method for TNBC is cytotoxic chemotherapy. However, the curative effect of chemotherapy is limited because of the existence of acquired or intrinsic multidrug resistance. MicroRNAs (miRNAs) are frequently dysregulated in malignant tumors and involved in tumor occurrence and progression. Interestingly, growing studies show that miRNAs are involved in chemoresistance in TNBC. Thus, targeting dysregulated miRNAs could be a plausible way for better treatment of TNBC. Here, we present the updated knowledge of miRNAs associated with chemoresistance in TNBC, which may be helpful for the early diagnosis, prognosis and treatment of this life-threatening disease.

Exploring the next generation of antibody-drug conjugates

Antibody-drug conjugates (ADCs) are a promising cancer treatment modality that enables the selective delivery of highly cytotoxic payloads to tumours. However, realizing the full potential of this platform necessitates innovative molecular designs to tackle several clinical challenges such as drug resistance, tumour heterogeneity and treatment-related adverse effects. Several emerging ADC formats exist, including bispecific ADCs, conditionally active ADCs (also known as probody-drug conjugates), immune-stimulating ADCs, protein-degrader ADCs and dual-drug ADCs, and each offers unique capabilities for tackling these various challenges. For example, probody-drug conjugates can enhance tumour specificity, whereas bispecific ADCs and dual-drug ADCs can address resistance and heterogeneity with enhanced activity. The incorporation of immune-stimulating and protein-degrader ADCs, which have distinct mechanisms of action, into existing treatment strategies could enable multimodal cancer treatment. Despite the promising outlook, the importance of patient stratification and biomarker identification cannot be overstated for these emerging ADCs, as these factors are crucial to identify patients who are most likely to derive benefit. As we continue to deepen our understanding of tumour biology and refine ADC design, we will edge closer to developing truly effective and safe ADCs for patients with treatment-refractory cancers. In this Review, we highlight advances in each ADC component (the monoclonal antibody, payload, linker and conjugation chemistry) and provide more-detailed discussions on selected examples of emerging novel ADCs of each format, enabled by engineering of one or more of these components.

Clinical and Genomic Characteristics of Patients with Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Metastatic Breast Cancer Following Progression on Cyclin-Dependent Kinase 4 and 6 Inhibitors

PURPOSE

We explored the clinical and genomic characteristics of hormone receptor-positive (HR+), HER2-negative (HER2-) metastatic breast cancer (MBC) after progression on cyclin-dependent kinase 4 and 6 inhibitors (CDK4 and 6i) ± endocrine therapy (ET) to understand potential resistance mechanisms that may aid in identifying treatment options.

EXPERIMENTAL DESIGN

Patients in the United States with HR+, HER2- MBC had tumor biopsies collected from a metastatic site during routine care following progression on a CDK4 and 6i ± ET (CohortPost) or prior to initiating CDK4 and 6i treatment (CohortPre) and analyzed using a targeted mutation panel and RNA-sequencing. Clinical and genomic characteristics were described.

RESULTS

The mean age at MBC diagnosis was 59 years in CohortPre (n = 133) and 56 years in CohortPost (n = 223); 14% and 45% of patients had prior chemotherapy/ET, and 35% and 26% had de novo stage IV MBC, respectively. The most common biopsy site was liver (CohortPre, 23%; CohortPost, 56%). CohortPost had significantly higher tumor mutational burden (TMB; median 3.16 vs. 1.67 Mut/Mb, P < 0.0001), ESR1 alteration frequency (mutations: 37% vs. 10%, FDR < 0.0001; fusions: 9% vs. 2%, P = 0.0176), and higher copy-number amplification of genes on chr12q15, including MDM2, FRS2, and YEATS4 versus patients in the CohortPre group. In addition, CDK4 copy-number gain on chr12q13 was significantly higher in CohortPost versus CohortPre (27% vs. 11%, P = 0.0005).

CONCLUSIONS

Distinct mechanisms potentially associated with resistance to CDK4 and 6i ± ET, including alterations in ESR1 and amplification of chr12q15 and CDK4 copy-number gain, were identified.

Identification of Candidate Therapeutic Genes for More Precise Treatment of Esophageal Squamous Cell Carcinoma and Adenocarcinoma

The standard therapy administered to patients with advanced esophageal cancer remains uniform, despite its two main histological subtypes, namely esophageal squamous cell carcinoma (SCC) and esophageal adenocarcinoma (AC), are being increasingly considered to be different. The identification of potential drug target genes between SCC and AC is crucial for more effective treatment of these diseases, given the high toxicity of chemotherapy and resistance to administered medications. Herein we attempted to identify and rank differentially expressed genes (DEGs) in SCC vs. AC using ensemble feature selection methods. RNA-seq data from The Cancer Genome Atlas and the Fudan-Taizhou Institute of Health Sciences (China). Six feature filters algorithms were used to identify DEGs. We built robust predictive models for histological subtypes with the random forest (RF) classification algorithm. Pathway analysis also be performed to investigate the functional role of genes. 294 informative DEGs (87 of them are newly discovered) have been identified. The areas under receiver operator curve (AUC) were higher than 99.5% for all feature selection (FS) methods. Nine genes (i.e., ERBB3, ATP7B, ABCC3, GALNT14, CLDN18, GUCY2C, FGFR4, KCNQ5, and CACNA1B) may play a key role in the development of more directed anticancer therapy for SCC and AC patients. The first four of them are drug targets for chemotherapy and immunotherapy of esophageal cancer and involved in pharmacokinetics and pharmacodynamics pathways. Research identified novel DEGs in SCC and AC, and detected four potential drug targeted genes (ERBB3, ATP7B, ABCC3, and GALNT14) and five drug-related genes.

Identification of vascular cues contributing to cancer cell stemness and function

Glioblastoma stem cells (GSCs) reside close to blood vessels (BVs) but vascular cues contributing to GSC stemness and the nature of GSC-BVs cross talk are not fully understood. Here, we dissected vascular cues influencing GSC gene expression and function to perfusion-based vascular cues, as well as to those requiring direct GSC-endothelial cell (EC) contacts. In light of our previous finding that perivascular tumor cells are metabolically different from tumor cells residing further downstream, cancer cells residing within a narrow, < 60 µm wide perivascular niche were isolated and confirmed to possess a superior tumor-initiation potential compared with those residing further downstream. To circumvent reliance on marker expression, perivascular GSCs were isolated from the respective locales based on their relative state of quiescence. Combined use of these procedures uncovered a large number of previously unrecognized differentially expressed GSC genes. We show that the unique metabolic milieu of the perivascular niche dominated by the highly restricted zone of mTOR activity is conducive for acquisition of GSC properties, primarily in the regulation of genes implicated in cell cycle control. A complementary role of vascular cues including those requiring direct glioma/EC contacts was revealed using glioma/EC co-cultures. Outstanding in the group of glioma cells impacted by nearby ECs were multiple genes responsible for maintaining GSCs in an undifferentiated state, a large fraction of which also relied on Notch-mediated signaling. Glioma-EC communication was found to be bidirectional, evidenced by extensive Notch-mediated EC reprogramming by contacting tumor cells, primarily metabolic EC reprogramming.

The Role of TRIP6, ABCC3 and CPS1 Expression in Resistance of Ovarian Cancer to Taxanes

The main problem precluding successful therapy with conventional taxanes is de novo or acquired resistance to taxanes. Therefore, novel experimental taxane derivatives (Stony Brook taxanes; SB-Ts) are synthesized and tested as potential drugs against resistant solid tumors. Recently, we reported alterations in ABCC3, CPS1, and TRIP6 gene expression in a breast cancer cell line resistant to paclitaxel. The present study aimed to investigate gene expression changes of these three candidate molecules in the highly resistant ovarian carcinoma cells in vitro and corresponding in vivo models treated with paclitaxel and new experimental Stony Brook taxanes of the third generation (SB-T-121605 and SB-T-121606). We also addressed their prognostic meaning in ovarian carcinoma patients treated with taxanes. We estimated and observed changes in mRNA and protein profiles of ABCC3, CPS1, and TRIP6 in resistant and sensitive ovarian cancer cells and after the treatment of resistant ovarian cancer models with paclitaxel and Stony Brook taxanes in vitro and in vivo. Combining Stony Brook taxanes with paclitaxel caused downregulation of CPS1 in the paclitaxel-resistant mouse xenograft tumor model in vivo. Moreover, CPS1 overexpression seems to play a role of a prognostic biomarker of epithelial ovarian carcinoma patients’ poor survival. ABCC3 was overexpressed in EOC tumors, but after the treatment with taxanes, its up-regulation disappeared. Based on our results, we can suggest ABCC3 and CPS1 for further investigations as potential therapeutic targets in human cancers.

Quantitative Evaluation of the Effect of Antigen Expression Level on Antibody-Drug Conjugate Exposure in Solid Tumor

Antibody-drug conjugates (ADCs) rely on high expression of target antigens on cancer cells to effectively enter the cell and release a cytotoxic payload. Previous studies have shown that ADC efficacy is not always tied to antigen expression. However, our recent in vitro study suggests a linear relationship between antigen expression and the intracellular levels of the ADC payload. In this study, we have explored the relationship between antigen expression and intratumoral ADC exposure in vivo. Using trastuzumab-vc-MMAE (T-vc-MMAE) and four cell lines with varying expression of human epithelial growth factor receptor 2 (HER2), the pharmacokinetics of total trastuzumab, released ("free") MMAE, and total MMAE were evaluated in a tumor xenograft model. Nude mice were implanted with tumors originating from BT-474, MDA-MB-453, MCF-7, and MDA-MB-468 cell lines and dosed with 10 mg/kg or 1 mg/kg of ADC. Observed data were mathematically characterized using a mechanism-based PK model. A strong positive correlation was observed between antigen expression levels and free/total MMAE exposure (R² ≥ 0.91) (total MMAE being the sum of released and conjugated MMAE) within the tumor, but not for total trastuzumab exposure. The PK model was able to recapitulate plasma PK through simulation; however, the tumor PK was overpredicted or underpredicted in some cases potentially due to differences in tumor vasculature or extracellular matrix conditions. Our results indicate a linear relationship between antigen expression and tumor exposure of free/total ADC payload in vivo, validating our previous finding in vitro, while also revealing the need to understand complex physiology of the tumor to predict tumor PK of ADC and its components. Our findings also support the concept of antigen expression screening in patients for targeted therapies like ADCs to achieve the maximum therapeutic benefit of the treatment.

Truncated HDAC9 identified by integrated genome-wide screen as the key modulator for paclitaxel resistance in triple-negative breast cancer

Rationale: Paclitaxel resistance is a major concern when treating triple-negative breast cancer (TNBC) patients. We aimed to identify candidates causing paclitaxel resistance and explore their significance in TNBC therapeutics. Methods: A genome-wide CRISPR screening, integrated with transcriptome analyses, was performed to identify candidates involved in paclitaxel-resistant TNBCs. Cell proliferation, cytotoxicity, immunofluorescent staining, and xenograft assays were conducted to verify the phenotypes of paclitaxel resistance induced by candidate genes, both in vitro and in vivo. RNA sequencing, Western blotting, and chromatin immunoprecipitation assays were used to explore the underlying mechanisms. Results: MEF2-interacting transcriptional repressor (MITR), the truncated isoform of histone deacetylase 9 (HDAC9) lacking the deacetylation domain, was enriched in paclitaxel-resistant cells. Elevated MITR expression resulted in increased interleukin-11 (IL11) expression and activation of downstream JAK/STAT3 signaling. Mechanistically, MITR counteracted MEF2A-induced transcriptional suppression of IL11, ultimately causing paclitaxel resistance. By contrast, pharmacological inhibition of JAK1/2 by ruxolitinib reversed paclitaxel resistance both in vitro and in vivo. Conclusion: Our in vitro and in vivo genetic and cellular analyses elucidated the pivotal role of MITR/MEF2A/IL11 axis in paclitaxel resistance and provided a novel therapeutic strategy for TNBC patients to overcome poor chemotherapy responses.

Therapy options after CDK4/6 inhibitors for HR+, HER2- postmenopausal metastatic/recurrent breast cancer in Japan: a role for mammalian target of rapamycin inhibitors?

Despite advances in the treatment of hormone receptor-positive, HER2- metastatic breast cancer, the disease is rarely curable. In this review, we focus on the use of CDK4/6 inhibitors, examining clinical experience and the mechanisms underlying the development of resistance, and evaluating treatment options after failure to respond to CDK4/6 inhibitors. Current basic research supports the use of mammalian target of rapamycin inhibitors after CDK4/6 inhibitor failure; however, more data are needed, particularly regarding treatment sequencing. Real-world data studies may help to fill the current knowledge gap, particularly where large-scale randomized controlled studies are not feasible.

Evaluation of Quantitative Relationship Between Target Expression and Antibody-Drug Conjugate Exposure Inside Cancer Cells

Antibody-drug conjugates (ADCs) employ overexpressed cell surface antigens to deliver cytotoxic payloads inside cancer cells. However, the relationship between target expression and ADC efficacy remains ambiguous. In this manuscript, we have addressed a part of this ambiguity by quantitatively investigating the effect of antigen expression levels on ADC exposure within cancer cells. Trastuzumab-valine-citrulline-monomethyl auristatin E was used as a model ADC, and four different cell lines with diverse levels of human epidermal growth factor receptor 2 (HER2) expression were used as model cells. The pharmacokinetics (PK) of total trastuzumab, released monomethyl auristatin E (MMAE), and total MMAE were measured inside the cells and in the cell culture media following incubation with two different concentrations of ADC. In addition, target expression levels, target internalization rate, and cathepsin B and MDR1 protein concentrations were determined for each cell line. All the PK data were mathematically characterized using a cell-level systems PK model for ADC. It was found that SKBR-3, MDA-MB-453, MCF-7, and MDA-MB-468 cells had ∼800,000, ∼250,000, ∼50,000, and ∼10,000 HER2 receptors per cell, respectively. A strong linear relationship (R ² > 0.9) was observed between HER2 receptor count and released MMAE exposure inside the cancer cells. There was an inverse relationship found between HER2 expression level and internalization rate, and cathepsin B and multidrug resistance protein 1 (MDR1) expression level varied slightly among the cell lines. The PK model was able to simultaneously capture all the PK profiles reasonably well while estimating only two parameters. Our results demonstrate a strong quantitative relationship between antigen expression level and intracellular exposure of ADCs in cancer cells. SIGNIFICANCE STATEMENT: In this manuscript, we have demonstrated a strong linear relationship between target expression level and antibody-drug conjugate (ADC) exposure inside cancer cells. We have also shown that this relationship can be accurately captured using the cell-level systems pharmacokinetics model developed for ADCs. Our results indirectly suggest that the lack of relationship between target expression and efficacy of ADC may stem from differences in the pharmacodynamic properties of cancer cells.

Curcumol enhances the sensitivity of doxorubicin in triple-negative breast cancer via regulating the miR-181b-2-3p-ABCC3 axis

Chemoresistance is a major cause of recurrence and poor prognosis in triple-negative breast cancer (TNBC) patients. The essential oil of Rhizoma Curcumae has been recently reported to enhance the chemosensitivity of cancer cells. However, few reports have systematically illuminated the mechanism. Curcumol is the major component of the essential oil of Rhizoma Curcumae. Therefore, we wondered whether curcumol combined with chemotherapy could increase the anticancer effects. In the present study, we evaluated the anticancer effects of doxorubicin and curcumol alone or in combination by a series of growth proliferation and apoptosis assays in TNBC cells. Our results showed that curcumol enhanced the sensitivity of MDA-MB-231 cells to doxorubicin in vitro and in vivo. Through miRNA-seq, we found that miR-181b-2-3p was involved in the curcumol-mediated promotion of doxorubicin-sensitivity in both parental and doxorubicin-resistant MDA-MB-231 (MDA-MB-231/ADR) cells. Further study showed that miR-181b-2-3p suppressed ABCC3 expression by targeting its 3'UTR. More importantly, we identified that overexpression of miR-181b-2-3p sensitized MDA-MB-231/ADR cells to doxorubicin by inhibiting the drug efflux transporter ABCC3. Furthermore, we found that NFAT1 could be activated by curcumol. In addition, ChIP assay results revealed that NFAT1 could directly bind to the promoter region of miR-181b-2-3p. Finally, using PDX models, we identified that curcumol could enhance sensitivity to doxorubicin to suppress tumor growth by the miR-181b-2-3p-ABCC3 axis in vivo. Taken together, our study provides novel mechanistic evidence for curcumol-mediated sensitization to doxorubicin in TNBC, and it highlights the potential therapeutic usefulness of curcumol as an adjunct drug in TNBC patients with doxorubicin-resistance.

Avidity-based binding to HER2 results in selective killing of HER2-overexpressing cells by anti-HER2/CD3

A primary barrier to the success of T cell-recruiting bispecific antibodies in the treatment of solid tumors is the lack of tumor-specific targets, resulting in on-target off-tumor adverse effects from T cell autoreactivity to target-expressing organs. To overcome this, we developed an anti-HER2/CD3 T cell-dependent bispecific (TDB) antibody that selectively targets HER2-overexpressing tumor cells with high potency, while sparing cells that express low amounts of HER2 found in normal human tissues. Selectivity is based on the avidity of two low-affinity anti-HER2 Fab arms to high target density on HER2-overexpressing cells. The increased selectivity to HER2-overexpressing cells is expected to mitigate the risk of adverse effects and increase the therapeutic index. Results included in this manuscript not only support the clinical development of anti-HER2/CD3 1Fab-immunoglobulin G TDB but also introduce a potentially widely applicable strategy for other T cell-directed therapies. The potential of this discovery has broad applications to further enable consideration of solid tumor targets that were previously limited by on-target, but off-tumor, autoimmunity.

Principal Component Analysis Based on Graph Laplacian and Double Sparse Constraints for Feature Selection and Sample Clustering on Multi-View Data

Principal component analysis (PCA) is a widely used method for evaluating low-dimensional data. Some variants of PCA have been proposed to improve the interpretation of the principal components (PCs). One of the most common methods is sparse PCA which aims at finding a sparse basis to improve the interpretability over the dense basis of PCA. However, the performances of these improved methods are still far from satisfactory because the data still contain redundant PCs. In this paper, a novel method called PCA based on graph Laplacian and double sparse constraints (GDSPCA) is proposed to improve the interpretation of the PCs and consider the internal geometry of the data. In detail, GDSPCA utilizes L2,1-norm and L1-norm regularization terms simultaneously to enforce the matrix to be sparse by filtering redundant and irrelative PCs, where the L2,1-norm regularization term can produce row sparsity, while the L1-norm regularization term can enforce element sparsity. This way, we can make a better interpretation of the new PCs in low-dimensional subspace. Meanwhile, the method of GDSPCA integrates graph Laplacian into PCA to explore the geometric structure hidden in the data. A simple and effective optimization solution is provided. Extensive experiments on multi-view biological data demonstrate the feasibility and effectiveness of the proposed approach.

Reproducibility of pharmacogenetics findings for paclitaxel in a heterogeneous population of patients with lung cancer

Pharmacogenetics studies have identified several allelic variants with the potential to reduce toxicity and improve treatment outcome. The present study was designed to determine if such findings are reproducible in a heterogenous population of patients with lung cancer undergoing therapy with paclitaxel. We designed a prospective multi-institutional study that recruited n = 103 patients receiving paclitaxel therapy with a 5-year follow up. All patients were genotyped using the Drug Metabolizing Enzymes and Transporters (DMET) platform, which ascertains 1931 genotypes in 235 genes. Progression-free survival (PFS) of paclitaxel therapy and clinically-significant paclitaxel toxicities were classified and compared according to genotype. Initial screening revealed eleven variants that are associated with PFS. Of these, seven variants in ABCB11 (rs4148768), ABCC3 (rs1051640), ABCG1 (rs1541290), CYP8B1 (rs735320), NR3C1 (rs6169), FMO6P (rs7889839), and GSTM3 (rs7483) were associated with paclitaxel PFS in a multivariate analysis accounting for clinical covariates. Multivariate analysis revealed four SNPs in VKORC1 (rs2884737), SLC22A14 (rs4679028), GSTA2 (rs6577), and DCK (rs4643786) were associated with paclitaxel toxicities. With the exception of a variant in VKORC1, the present study did not find the same genetic outcome associations of other published research on pharmacogenetics variants that affect paclitaxel outcomes. This finding suggests that prior pharmacogenomics research findings may not be reproduced in the most frequently-diagnosed malignancy, lung cancer.

Genomic region detection via Spatial Convex Clustering

Several modern genomic technologies, such as DNA-Methylation arrays, measure spatially registered probes that number in the hundreds of thousands across multiple chromosomes. The measured probes are by themselves less interesting scientifically; instead scientists seek to discover biologically interpretable genomic regions comprised of contiguous groups of probes which may act as biomarkers of disease or serve as a dimension-reducing pre-processing step for downstream analyses. In this paper, we introduce an unsupervised feature learning technique which maps technological units (probes) to biological units (genomic regions) that are common across all subjects. We use ideas from fusion penalties and convex clustering to introduce a method for Spatial Convex Clustering, or SpaCC. Our method is specifically tailored to detecting multi-subject regions of methylation, but we also test our approach on the well-studied problem of detecting segments of copy number variation. We formulate our method as a convex optimization problem, develop a massively parallelizable algorithm to find its solution, and introduce automated approaches for handling missing values and determining tuning parameters. Through simulation studies based on real methylation and copy number variation data, we show that SpaCC exhibits significant performance gains relative to existing methods. Finally, we illustrate SpaCC's advantages as a pre-processing technique that reduces large-scale genomics data into a smaller number of genomic regions through several cancer epigenetics case studies on subtype discovery, network estimation, and epigenetic-wide association.

Substituents at the C3' and C3'N positions are critical for taxanes to overcome acquired resistance of cancer cells to paclitaxel

We tested the role of substituents at the C3' and C3'N positions of the taxane molecule to identify taxane derivatives capable of overcoming acquired resistance to paclitaxel. Paclitaxel-resistant sublines SK-BR-3/PacR and MCF-7/PacR as well as the original paclitaxel-sensitive breast cancer cell lines SK-BR-3 and MCF-7 were used for testing. Increased expression of the ABCB1 transporter was found to be involved in the acquired resistance. We tested three groups of taxane derivatives: (1) phenyl group at both C3' and C3'N positions, (2) one phenyl at one of the C3' and C3'N positions and a non-aromatic group at the second position, (3) a non-aromatic group at both C3' and C3'N positions. We found that the presence of phenyl groups at both C3' and C3'N positions is associated with low capability of overcoming acquired paclitaxel resistance compared to taxanes containing at least one non-aromatic substituent at the C3' and C3'N positions. The increase in the ATPase activity of ABCB1 transporter after the application of taxanes from the first group was found to be somewhat higher than after the application of taxanes from the third group. Molecular docking studies demonstrated that the docking score was the lowest, i.e. the highest binding affinity, for taxanes from the first group. It was intermediate for taxanes from the second group, and the highest for taxanes from the third group. We conclude that at least one non-aromatic group at the C3' and C3'N positions of the taxane structure, resulting in reduced affinity to the ABCB1 transporter, brings about high capability of taxane to overcome acquired resistance of breast cancer cells to paclitaxel, due to less efficient transport of the taxane compound out of the cancer cells.

A monomethyl auristatin E-conjugated antibody to guanylyl cyclase C is cytotoxic to target-expressing cells in vitro and in vivo

Guanylyl cyclase C (GCC) is a cell-surface protein that is expressed by normal intestinal epithelial cells, more than 95% of metastatic colorectal cancers (mCRC), and the majority of gastric and pancreatic cancers. Due to strict apical localization, systemically delivered GCC-targeting agents should not reach GCC in normal intestinal tissue, while accessing antigen in tumor. We generated an investigational antibody-drug conjugate (TAK-264, formerly MLN0264) comprising a fully human anti-GCC monoclonal antibody conjugated to monomethyl auristatin E via a protease-cleavable peptide linker. TAK-264 specifically bound, was internalized by, and killed GCC-expressing cells in vitro in an antigen-density-dependent manner. In GCC-expressing xenograft models with similar GCC expression levels/patterns observed in human mCRC samples, TAK-264 induced cell death, leading to tumor regressions and long-term tumor growth inhibition. TAK-264 antitumor activity was generally antigen-density-dependent, although some GCC-expressing tumors were refractory to TAK-264-targeted high local concentrations of payload. These data support further evaluation of TAK-264 in the treatment of GCC-expressing tumors.

Membrane-Proximal Epitope Facilitates Efficient T Cell Synapse Formation by Anti-FcRH5/CD3 and Is a Requirement for Myeloma Cell Killing

The anti-FcRH5/CD3 T cell-dependent bispecific antibody (TDB) targets the B cell lineage marker FcRH5 expressed in multiple myeloma (MM) tumor cells. We demonstrate that TDBs trigger T cell receptor activation by inducing target clustering and exclusion of CD45 phosphatase from the synapse. The dimensions of the target molecule play a key role in the efficiency of the synapse formation. The anti-FcRH5/CD3 TDB kills human plasma cells and patient-derived myeloma cells at picomolar concentrations and results in complete depletion of B cells and bone marrow plasma cells in cynomolgus monkeys. These data demonstrate the potential for the anti-FcRH5/CD3 TDB, alone or in combination with inhibition of PD-1/PD-L1 signaling, in the treatment of MM and other B cell malignancies.

Orthogonal Cysteine Protection Enables Homogeneous Multi-Drug Antibody-Drug Conjugates

A strategy for the preparation of homogeneous antibody–drug conjugates (ADCs) containing multiple payloads has been developed. This approach utilizes sequential unmasking of cysteine residues with orthogonal protection to enable site‐specific conjugation of each drug. In addition, because the approach utilizes conjugation to native antibody cysteine residues, it is widely applicable and enables high drug loading for improved ADC potency. To highlight the benefits of ADC dual drug delivery, this strategy was applied to the preparation of ADCs containing two classes of auristatin drug‐linkers that have differing physiochemical properties and exert complementary anti‐cancer activities. Dual‐auristatin ADCs imparted activity in cell line and xenograft models that are refractory to ADCs comprised of the individual auristatin components. This work presents a facile method for construction of potent dual‐drug ADCs and demonstrates how delivery of multiple cytotoxic warheads can lead to improved ADC activities. Lastly, we anticipate that the conditions utilized herein for orthogonal cysteine unmasking are not restricted to ADCs and can be broadly utilized for site‐specific protein modification.

Characterization of acquired paclitaxel resistance of breast cancer cells and involvement of ABC transporters

Development of taxane resistance has become clinically very important issue. The molecular mechanisms underlying the resistance are still unclear. To address this issue, we established paclitaxel-resistant sublines of the SK-BR-3 and MCF-7 breast cancer cell lines that are capable of long-term proliferation in 100nM and 300nM paclitaxel, respectively. Application of these concentrations leads to cell death in the original counterpart cells. Both sublines are cross-resistant to doxorubicin, indicating the presence of the MDR phenotype. Interestingly, resistance in both paclitaxel-resistant sublines is circumvented by the second-generation taxane SB-T-1216. Moreover, we demonstrated that it was not possible to establish sublines of SK-BR-3 and MCF-7 cells resistant to this taxane. It means that at least the tested breast cancer cells are unable to develop resistance to some taxanes. Employing mRNA expression profiling of all known human ABC transporters and subsequent Western blot analysis of the expression of selected transporters, we demonstrated that only the ABCB1/PgP and ABCC3/MRP3 proteins were up-regulated in both paclitaxel-resistant sublines. We found up-regulation of ABCG2/BCRP and ABCC4 proteins only in paclitaxel-resistant SK-BR-3 cells. In paclitaxel-resistant MCF-7 cells, ABCB4/MDR3 and ABCC2/MRP2 proteins were up-regulated. Silencing of ABCB1 expression using specific siRNA increased significantly, but did not completely restore full sensitivity to both paclitaxel and doxorubicin. Thus we showed a key, but not exclusive, role for ABCB1 in mechanisms of paclitaxel resistance. It suggests the involvement of multiple mechanisms in paclitaxel resistance in tested breast cancer cells.

Antibody-Drug Conjugates for Cancer Therapy

Antibody–drug conjugates (ADCs) take advantage of the specificity of a monoclonal antibody to deliver a linked cytotoxic agent directly into a tumour cell. The development of these compounds provides exciting opportunities for improvements in patient care. Here, we review the key issues impacting on the clinical success of ADCs in cancer therapy. Like many other developing therapeutic classes, there remain challenges in the design and optimisation of these compounds. As the clinical applications for ADCs continue to expand, key strategies to improve patient outcomes include better patient selection for treatment and the identification of mechanisms of therapy resistance.

Redox Control of Multidrug Resistance and Its Possible Modulation by Antioxidants

Clinical efficacy of anticancer chemotherapies is dramatically hampered by multidrug resistance (MDR) dependent on inherited traits, acquired defence against toxins, and adaptive mechanisms mounting in tumours. There is overwhelming evidence that molecular events leading to MDR are regulated by redox mechanisms. For example, chemotherapeutics which overrun the first obstacle of redox-regulated cellular uptake channels (MDR1, MDR2, and MDR3) induce a concerted action of phase I/II metabolic enzymes with a temporal redox-regulated axis. This results in rapid metabolic transformation and elimination of a toxin. This metabolic axis is tightly interconnected with the inducible Nrf2-linked pathway, a key switch-on mechanism for upregulation of endogenous antioxidant enzymes and detoxifying systems. As a result, chemotherapeutics and cytotoxic by-products of their metabolism (ROS, hydroperoxides, and aldehydes) are inactivated and MDR occurs. On the other hand, tumour cells are capable of mounting an adaptive antioxidant response against ROS produced by chemotherapeutics and host immune cells. The multiple redox-dependent mechanisms involved in MDR prompted suggesting redox-active drugs (antioxidants and prooxidants) or inhibitors of inducible antioxidant defence as a novel approach to diminish MDR. Pitfalls and progress in this direction are discussed.

Potential targets for ovarian clear cell carcinoma: a review of updates and future perspectives

Advances in surgical and medical treatments for ovarian cancer have improved prognoses. Platinum drugs in particular are pivotal for the medical treatment of ovarian cancer. However, previous studies have revealed that some histological subtypes, such as clear cell carcinoma, are resistant to medical treatment, including that with platinum drugs. Consequently, the clinical prognosis of advanced clear cell carcinoma is remarkably inferior, primarily because of its chemoresistant behavior. The prevalence of clear cell carcinoma is approximately 5 % in the West, but in Japan, its prevalence is particularly high, at approximately 25 %. Current medical treatments for advanced clear cell carcinoma are difficult to administer, and they have poor efficacy, warranting the development of novel target-based therapies. In this review, we describe medical treatments for clear cell carcinoma and discuss future prospects for therapy. In particular, we focus on the mechanism of platinum resistance in clear cell carcinoma, including the role of annexin A4, one of the most investigated factors of platinum resistance, as well as the mutant genes and overexpressed proteins such as VEGF, PI3K/AKT/mTOR signaling pathway, ARID1A, hepatocyte nuclear factor-1β, ZNF217. We also review targeted molecular therapeutics for epithelial ovarian cancer and discuss their role in clear cell carcinoma treatment. We review the drugs targeting angiogenesis (bevacizumab, sorafenib, and pazopanib), growth factors (gefitinib, erlotinib, lapatinib, trastuzumab, and AMG479), and signaling pathways (temsirolimus, dasatinib, and imatinib), and other drugs (oregovomab, volociximab, and iniparib). This current review summarizes and discusses the clinical significance of these factors in ovarian clear cell carcinoma as well as their potential mechanisms of action. It may provide new integrative understanding for future studies on their exact role in ovarian clear cell carcinoma.

Resveratrol chemosensitizes HER-2-overexpressing breast cancer cells to docetaxel chemoresistance by inhibiting docetaxel-mediated activation of HER-2-Akt axis

As breast cancer cells often develop chemoresistance, better therapeutic options are in search to circumvent it. Here we demonstrate that human epidermal growth factor receptor-2 (HER-2)-overexpressing breast cancer cells resist docetaxel-induced cytotoxicity by upregulating HER-2 and its activity downstream, through Akt and mitogen-activated protein kinase (MAPK) pathways. We observed that introducing resveratrol as a chemosensitizer in docetaxel chemotherapy blocks upregulation and activation of HER-2 in addition to blocking downstream signaling pathways such as Akt. Resveratrol and docetaxel combination results in the synergistic induction of cell death in HER-2-overexpressing SK-BR-3 cells, whereas introduction of wild-type HER-2 in MDA-MD-231 cells increased the resistance to docetaxel. Dominant-negative HER-2 sensitizes SK-BR-3 cells to docetaxel. Our study identified a new synergistic therapeutic combination that targets HER-2-induced breast cancer resistance and might help to overcome therapeutic resistance during breast cancer therapy. The synergism of docetaxel and resveratrol was maximum in SK-BR-3, which is unique among the cell lines studied, due to its high expression status of HER-2, a receptor known to dictate the signaling environment of breast cancer cells. Docetaxel could further induce HER-2 activity in these cells, which was downregulated on resveratrol treatment. Transfection of DN-HER-2 in SK-BR-3 cells inhibits the synergism as the transfection itself sensitizes these cells to docetaxel, leaving no role for resveratrol, whereas ectopic expression of HER-2 introduces the synergism in MDA-MB-231, the triple-negative cell line, in which the synergism was minimum, attesting the crucial role of HER-2 in suppressing the sensitivity to docetaxel. Single-agent docetaxel induced HER-2-mediated resistance to cell death, which was blocked by resveratrol. Resveratrol also downregulated docetaxel-induced activation of MAPK and Akt, survival signaling pathways downstream of HER-2. In short, this study, for the first time, establishes the role of HER-2–Akt signaling axis in regulating the synergistic effect of docetaxel and resveratrol in breast cancer cells overexpressing HER-2.

PTEN loss in circulating tumour cells correlates with PTEN loss in fresh tumour tissue from castration-resistant prostate cancer patients

Background:

PTEN gene loss occurs frequently in castration-resistant prostate cancer (CRPC) and may drive progression through activation of the PI3K/AKT pathway. Here, we developed a novel CTC-based assay to determine PTEN status and examined the correlation between PTEN status in CTCs and matched tumour tissue samples.

Methods:

PTEN gene status in CTCs was evaluated on an enrichment-free platform (Epic Sciences) by fluorescence in situ hybridisation (FISH). PTEN status in archival and fresh tumour tissue was evaluated by FISH and immunohistochemistry.

Results:

Peripheral blood was collected from 76 patients. Matched archival and fresh cancer tissue was available for 48 patients. PTEN gene status detected in CTCs was concordant with PTEN status in matched fresh tissues and archival tissue in 32 of 38 patients (84%) and 24 of 39 patients (62%), respectively. CTC counts were prognostic (continuous, P=0.001). PTEN loss in CTCs associated with worse survival in univariate analysis (HR 2.05; 95% CI 1.17–3.62; P=0.01) and with high lactate dehydrogenase (LDH) in metastatic CRPC patients.

Conclusions:

Our results illustrate the potential use of CTCs as a non-invasive, real-time liquid biopsy to determine PTEN gene status. The prognostic and predictive value of PTEN in CTCs warrants investigation in CRPC clinical trials of PI3K/AKT-targeted therapies.

Results of a Multicenter Phase II Trial of Brentuximab Vedotin as Second-Line Therapy before Autologous Transplantation in Relapsed/Refractory Hodgkin Lymphoma

This multicenter prospective phase II study examines the activity and tolerability of brentuximab vedotin as second-line therapy in patients with Hodgkin lymphoma that was relapsed or refractory after induction therapy. Brentuximab vedotin (1.8 mg/kg) was administered i.v. on day 1 of a 21-day cycle for a total of 4 cycles. Patients then proceeded to autologous hematopoietic cell transplantation (AHCT), if eligible, with or without additional salvage therapy, based on remission status after brentuximab vedotin. The primary endpoint was overall response rate (ORR). Secondary endpoints were safety, stem cell mobilization/collection, AHCT outcomes, and association of CD68(+) with outcomes. Of 37 patients, the ORR was 68% (13 complete remission, 12 partial remission). The regimen was well tolerated with few grade 3/4 adverse events, including lymphopenia (1), neutropenia (3), rash (2), and hyperuricemia (1). Thirty-two patients (86%) were able to proceed to AHCT, with 24 patients (65%) in complete remission at time of AHCT. Thirteen patients in complete remission, 4 in partial remission, and 1 with stable disease (49%) received AHCT without salvage combination chemotherapy. CD68 expression did not correlate with response to brentuximab vedotin. The median number of stem cells mobilized was 6.0 × 10(6) (range, 2.6 to 34), and median number of days to obtain minimum collection (2 × 10(6)) was 2 (range, 1 to 6). Brentuximab vedotin as second-line therapy is active, well tolerated, and allows adequate stem cell collection and engraftment. For Hodgkin lymphoma patients with relapsed/refractory disease after induction therapy, second-line brentuximab vedotin, followed by combination chemotherapy for residual disease, can effectively bridge patients to AHCT.

CD30 Downregulation, MMAE Resistance, and MDR1 Upregulation Are All Associated with Resistance to Brentuximab Vedotin

Brentuximab vedotin (BV) is an antibody-drug conjugate that specifically delivers the potent cytotoxic drug monomethyl auristatin E (MMAE) to CD30-positive cells. BV is FDA approved for treatment of relapsed/refractory Hodgkin lymphoma and anaplastic large cell lymphoma (ALCL); however, many patients do not achieve complete remission and develop BV-resistant disease. We selected for BV-resistant Hodgkin lymphoma (L428) and ALCL (Karpas-299) cell lines using either constant (ALCL) or pulsatile (Hodgkin lymphoma) exposure to BV. We confirmed drug resistance by MTS assay and analyzed CD30 expression in resistant cells by flow cytometry, qRT-PCR, and Western blotting. We also measured drug exporter expression, MMAE resistance, and intracellular MMAE concentrations in BV-resistant cells. In addition, tissue biopsy samples from 10 Hodgkin lymphoma and 5 ALCL patients who had relapsed or progressed after BV treatment were analyzed by immunohistocytochemistry for CD30 expression. The resistant ALCL cell line, but not the Hodgkin lymphoma cell line, demonstrated downregulated CD30 expression compared with the parental cell line. In contrast, the Hodgkin lymphoma cell line, but not the ALCL cell line, exhibited MMAE resistance and increased expression of the MDR1 drug exporter compared with the parental line. For both Hodgkin lymphoma and ALCL, samples from patients relapsed/resistant on BV persistently expressed CD30 by immunohistocytochemistry. One Hodgkin lymphoma patient sample expressed MDR1 by immunohistocytochemistry. Although loss of CD30 expression is a possible mode of BV resistance in ALCL in vitro models, this has not been confirmed in patients. MMAE resistance and MDR1 expression are possible modes of BV resistance for Hodgkin lymphoma both in vitro and in patients.

Antibody-targeted drugs and drug resistance--challenges and solutions

Antibody-based therapy of various human malignancies has shown efficacy in the past 30 years and is now one of the most successful and leading strategies for targeted treatment of patients harboring hematological malignancies and solid tumors. Antibody-drug conjugates (ADCs) aim to take advantage of the affinity and specificity of monoclonal antibodies (mAbs) to selectively deliver potent cytotoxic drugs to antigen-expressing tumor cells. Key parameters for ADC include choosing the optimal components of the ADC (the antibody, the linker and the cytotoxic drug) and selecting the suitable cell-surface target antigen. Building on the success of recent FDA approval of brentuximab vedotin (Adcetris) and ado-trastuzumab emtansine (Kadcyla), ADCs are currently a class of drugs with a robust pipeline with clinical applications that are rapidly expanding. The more ADCs are being evaluated in preclinical models and clinical trials, the clearer are becoming the parameters and the challenges required for their therapeutic success. This rapidly growing knowledge and clinical experience are revealing novel modalities and mechanisms of resistance to ADCs, hence offering plausible solutions to such challenges. Here, we review the key parameters for designing a powerful ADC, focusing on how ADCs are addressing the challenge of multiple drug resistance (MDR) and its rational overcoming.

Molecular characterisation of isogenic taxane resistant cell lines identify novel drivers of drug resistance

Background

Taxanes such as paclitaxel and docetaxel are used successfully to treat breast cancer, usually in combination with other agents. They interfere with microtubules causing cell cycle arrest; however, the mechanisms underlying the clinical effects of taxanes are yet to be fully elucidated.

Methods

Isogenic paclitaxel resistant (PACR) MDA‒MB‒231, paclitaxel resistant ZR75‒1 and docetaxel resistant (DOCR) ZR75‒1 cell lines were generated by incrementally increasing taxane dose in native cell lines in vitro. We used aCGH analysis to identify mechanisms driving taxane resistance.

Results

Taxane resistant cell lines exhibited an 18-170 fold increased resistance to taxanes, with the ZR75-1 resistant cell lines also demonstrating cross resistance to anthracyclines. Paclitaxel treatment of native cells resulted in a G2/M block and a decrease in the G1 phase of the cell cycle. However, in the resistant cell lines, minimal changes were present. Functional network analysis revealed that the mitotic prometaphase was lost in the resistant cell lines.

Conclusion

This study established a model system for examining taxane resistance and demonstrated that both MDR and mitosis represent common mechanism of taxane resistance.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-762) contains supplementary material, which is available to authorized users.

Gene signatures of drug resistance predict patient survival in colorectal cancer

Different combinations of 5-fluorouracil (5-FU), oxaliplatin, irinotecan and other newly developed agents have been used to treat colorectal cancer. Despite the advent of new treatment regimens, the 5-year survival rate for metastatic colorectal cancer remains low (~10%). Knowing the drug sensitivity of a given tumor for a particular agent could significantly impact decision making and treatment planning. Biomarkers are proven to be successful in characterizing patients into different response groups. Using survival prediction analysis, we have identified three independent gene signatures, which are associated with sensitivity of colorectal cancer cells to 5-FU, oxaliplatin or irinotecan. On the basis of the three gene signatures, three score systems were developed to stratify patients from sensitive to resistance. These score systems exhibited robustness in stratify patients in two independent clinical studies. Patients with high scores in all three drugs exhibited the lowest survival.

Polymorphisms of the drug transporters ABCB1, ABCG2, ABCC2 and ABCC3 and their impact on drug bioavailability and clinical relevance

INTRODUCTION

Human ATP-binding cassette (ABC) transporters act as translocators of numerous substrates across extracellular and intracellular membranes, thereby contributing to bioavailability and consequently therapy response. Genetic polymorphisms are considered as critical determinants of expression level or activity and subsequently response to selected drugs.

AREAS COVERED

Here the influence of polymorphisms of the prominent ABC transporters P-glycoprotein (MDR1, ABCB1), breast cancer resistance protein (BCRP, ABCG2) and the multidrug resistance-associated protein (MRP) 2 (ABCC2) as well as MRP3 (ABCC3) on the pharmacokinetic of drugs and associated consequences on therapy response and clinical outcome is discussed.

EXPERT OPINION

ABC transporter genetic variants were assumed to affect interindividual differences in pharmacokinetics and subsequently clinical response. However, decades of medical research have not yielded in distinct and unconfined reproducible outcomes. Despite some unique results, the majority were inconsistent and dependent on the analyzed cohort or study design. Therefore, variability of bioavailability and drug response may be attributed only by a small amount to polymorphisms in transporter genes, whereas transcriptional regulation or post-transcriptional modification seems to be more critical. In our opinion, currently identified genetic variants of ABC efflux transporters can give some hints on the role of transporters at interfaces but are less suitable as biomarkers to predict therapeutic outcome.

Depletion of the aryl hydrocarbon receptor in MDA-MB-231 human breast cancer cells altered the expression of genes in key regulatory pathways of cancer

The aryl hydrocarbon receptor (AhR), a transcription factor that is best known for its role in mediating the toxic responses elicited by poly aromatic hydrocarbons as well as many other environmental factors; is also involved in breast cancer progression. We previously reported that stable knockdown of AhR decreased the tumorigenic properties of the highly metastatic MDA-MB-231 breast cancer cell line; whereas ectopic overexpression of AhR was sufficient to transform immortalized human mammary epithelial cells to exhibit malignant phenotypes. In the present study we investigated the genes that are differentially regulated by AhR and are controlling cellular processes linked to breast cancer. We used Affymetrix Human GeneChip 1.0-ST whole transcriptome arrays to analyze alterations of gene expression resulting from stable AhR knockdown in the MDA-MB-231 breast cancer cell line. The expression of 144 genes was significantly altered with a ≥2.0-fold change and a multiple test corrected p-value ≤0.05, as a result of AhR knockdown. We demonstrate that AhR knockdown alters the expression of several genes known to be linked to cancer. These genes include those involved in tryptophan metabolism (KYNU), cell growth (MUC1 and IL8), cell survival (BIRC3 and BCL3), cell migration and invasion (S100A4 and ABI3), multi-drug resistance (ABCC3) and angiogenesis (VEGFA and CCL2). The identification of the genes and pathways affected by AhR depletion provides new insight into possible molecular events that could explain the reported phenotypic changes. In conclusion AhR knockdown alters the expression of genes known to enhance or inhibit cancer progression; tipping the balance towards a state that counteracts tumor progression.

MicroRNA-dependent regulation of transcription in non-small cell lung cancer

Squamous cell lung cancer (SCC) and adenocarcinoma are the most common histological subtypes of non-small cell lung cancer (NSCLC), and have been traditionally managed in the clinic as a single entity. Increasing evidence, however, illustrates the biological diversity of these two histological subgroups of lung cancer, and supports the need to improve our understanding of the molecular basis beyond the different phenotypes if we aim to develop more specific and individualized targeted therapy. The purpose of this study was to identify microRNA (miRNA)-dependent transcriptional regulation differences between SCC and adenocarcinoma histological lung cancer subtypes. In this work, paired miRNA (667 miRNAs by TaqMan Low Density Arrays (TLDA)) and mRNA profiling (Whole Genome 44 K array G112A, Agilent) was performed in tumor samples of 44 NSCLC patients. Nine miRNAs and 56 mRNAs were found to be differentially expressed in SCC versus adenocarcinoma samples. Eleven of these 56 mRNA were predicted as targets of the miRNAs identified to be differently expressed in these two histological conditions. Of them, 6 miRNAs (miR-149, miR-205, miR-375, miR-378, miR-422a and miR-708) and 9 target genes (CEACAM6, CGN, CLDN3, ABCC3, MLPH, ACSL5, TMEM45B, MUC1) were validated by quantitative PCR in an independent cohort of 41 lung cancer patients. Furthermore, the inverse correlation between mRNAs and microRNAs expression was also validated. These results suggest miRNA-dependent transcriptional regulation differences play an important role in determining key hallmarks of NSCLC, and may provide new biomarkers for personalized treatment strategies.

Germline pharmacogenetics of paclitaxel for cancer treatment

Paclitaxel is a highly effective chemotherapeutic agent used in a variety of solid tumors. Some paclitaxel-treated patients experience the intended therapeutic response with manageable side effects, while others have minimal response and/or severe toxicity. This variability in treatment outcome is partially determined by variability in drug exposure (pharmacokinetics) and by patient and tumor sensitivity (pharmacodynamics). Both pharmacokinetics and pharmacodynamics are dictated in part by common variants in the germline genome, known as SNPs. This article reviews the published literature on paclitaxel pharmacogenetics in cancer, focusing primarily on polymorphisms in genes relevant to paclitaxel pharmacokinetics and discusses preliminary work on pharmacodynamic genes and genome-wide association studies.

Targeted biomarker profiling of matched primary and metastatic estrogen receptor positive breast cancers

Patients with newly diagnosed, early stage estrogen receptor positive (ER+) breast cancer often show disease free survival in excess of five years following surgery and systemic adjuvant therapy. An important question is whether diagnostic tumor tissue from the primary lesion offers an accurate molecular portrait of the cancer post recurrence and thus may be used for predictive diagnostic purposes for patients with relapsed, metastatic disease. As the class I phosphatidylinositol 3' kinase (PI3K) pathway is frequently activated in ER+ breast cancer and has been linked to acquired resistance to hormonal therapy, we hypothesized pathway status could evolve over time and treatment. Biomarker analyses were conducted on matched, asynchronous primary and metastatic tumors from 77 patients with ER+ breast cancer. We examined whether PIK3CA and AKT1 alterations or PTEN and Ki67 levels showed differences between primary and metastatic samples. We also sought to look more broadly at gene expression markers reflective of proliferation, molecular subtype, and key receptors and signaling pathways using an mRNA analysis platform developed on the Fluidigm BioMark™ microfluidics system to measure the relative expression of 90 breast cancer related genes in formalin-fixed paraffin-embedded (FFPE) tissue. Application of this panel of biomarker assays to matched tumor pairs showed a high concordance between primary and metastatic tissue, with generally few changes in mutation status, proliferative markers, or gene expression between matched samples. The collection of assays described here has been optimized for FFPE tissue and may have utility in exploratory analyses to identify patient subsets responsive to targeted therapies.

Acquired PIK3CA amplification causes resistance to selective phosphoinositide 3-kinase inhibitors in breast cancer

Agents targeting the PI3K/mTOR signaling axis have shown promise in early-phase clinical trials and are currently being studied in later stages of clinical development in multiple indications. Experience with other targeted agents suggests that clinical responses may be short-lived because of acquired resistance to therapy. Here, we report preclinical modeling of acquired resistance in a HER2-positive, PIK3CA mutant breast cancer cell line, KPL-4. We identified a heretofore-unreported mechanism of resistance, specifically high-level amplification of the mutant allele of PIK3CA, which resulted in a marked upregulation of PI3K signaling, enabling resistant cells to regain proliferative capacity at clinically relevant concentrations of the PI3K inhibitor, GDC-0941. We show that knockdown of the amplified PIK3CA mutant allele in these cells by small interfering RNA restored pathway signaling and sensitivity to PI3K inhibition at levels comparable to parental cells. These novel preclinical findings suggest that, in addition to assessment of other previously reported mechanisms of resistance, evaluation of PI3K copy number variation should be integrated into the exploratory analysis of biopsies obtained at disease progression.

ABCC3 as a marker for multidrug resistance in non-small cell lung cancer

Multidrug resistance (MDR) contributes to the failure of chemotherapy and high mortality in non-small cell lung cancer (NSCLC). We aim to identify MDR genes that predict tumor response to chemotherapy. 199 NSCLC fresh tissue samples were tested for chemosensitivity by MTT assay. cDNA microarray was done with 5 samples with highest resistance and 6 samples with highest sensitivity. Expression of ABCC3 mRNA and protein was detected by real-time PCR and immunohistochemisty, respectively. The association between gene expression and overall survival (OS) was examined using Cox proportional hazard regression. 44 genes were upregulated and 168 downregulated in the chemotherapy-resistant group. ABCC3 was one of the most up-regulated genes in the resistant group. ABCC3-positive expression correlated with lymph node involvement, advanced TNM stage, more malignant histological type, multiple-resistance to anti-cancer drugs, and reduced OS. ABCC3 expression may serve as a marker for MDR and predictor for poor clinical outcome of NSCLC.

In vitro three-dimensional modeling of fallopian tube secretory epithelial cells

Background

Fallopian tube secretory epithelial cells (FTSECs) have been implicated as a cell-of-origin for high-grade serous epithelial ovarian cancer. However, there are relatively few in vitro models of this tissue type available for use in studies of FTSEC biology and malignant transformation. In vitro three-dimensional (3D) cell culture models aim to recreate the architecture and geometry of tissues in vivo and restore the complex network of cell-cell/cell-matrix interactions that occur throughout the surface of the cell membrane.

Results

We have established and characterized 3D spheroid culture models of primary FTSECs. FTSEC spheroids contain central cores of hyaline matrix surrounded by mono- or multi-layer epithelial sheets. We found that 3D culturing alters the molecular characteristics of FTSECs compared to 2D cultures of the same cells. Gene expression profiling identified more than a thousand differentially expressed genes between 3D and 2D cultures of the same FTSEC lines. Pathways significantly under-represented in 3D FTSEC cultures were associated with cell cycle progression and DNA replication. This was also reflected in the reduced proliferative indices observed in 3D spheroids stained for the proliferation marker MIB1. Comparisons with gene expression profiles of fresh fallopian tube tissues revealed that 2D FTSEC cultures clustered with follicular phase tubal epithelium, whereas 3D FTSEC cultures clustered with luteal phase samples.

Conclusions

This 3D model of fallopian tube secretory epithelial cells will advance our ability to study the underlying biology and etiology of fallopian tube tissues and the pathogenesis of high-grade serous epithelial ovarian cancer.

Anti-Neoplastic Cytotoxicity of Gemcitabine-(C4-amide)-[anti-HER2/neu] in Combination with Griseofulvin against Chemotherapeutic-Resistant Mammary Adenocarcinoma (SKBr-3)

Introduction

Gemcitabine is a pyrimidine nucleoside analog that becomes triphosphorylated and in this form it competitively inhibits cytidine incorporation into DNA strands. Diphosphorylated gemcitabine irreversibly inhibits ribonucleotide reductase thereby preventing deoxyribonucleotide synthesis. Functioning as a potent chemotherapeutic, gemcitabine decreases neoplastic cell proliferation and induces apoptosis which accounts for its effectiveness in the clinical treatment of several leukemia and carcinoma cell types. A brief plasma half-life due to rapid deamination, chemotherapeuticresistance and sequelae restricts gemcitabine utility in clinical oncology. Selective “targeted” gemcitabine delivery represents a molecular strategy for prolonging its plasma half-life and minimizing innocent tissue/organ exposure.

Methods

A previously described organic chemistry scheme was applied to synthesize a UV-photoactivated gemcitabine intermediate for production of gemcitabine-(C₄-amide)-[anti-HER2/neu]. Immunodetection analysis (Western-blot) was applied to detect the presence of any degradative fragmentation or polymerization. Detection of retained binding-avidity for gemcitabine-(C₄-amide)-[anti-HER2/neu] was determined by cell-ELISA using populations of chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) that highly over-express the HER2/neu trophic membrane receptor. Anti-neoplastic cytotoxicity of gemcitabine-(C₄-amide)-[anti-HER2/neu] and the tubulin/microtubule inhibitor, griseofulvin was established against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3). Related investigations evaluated the potential for gemcitabine-(C₄-amide)-[anti-HER2/neu] in dual combination with griseofulvin to evoke increased levels of anti-neoplastic cytotoxicity compared to gemcitabine-(C₄-amide)-[anti-HER2/neu].

Results

Covalent gemcitabine-(C₄-amide)-[anti-HER2/neu] immunochemotherapeutic and griseofulvin exerted anti-neoplastic cytotoxicity against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3). Covalent gemcitabine-(C₄-amide)-[anti-HER2/neu] immunochemotherapeutic or gemcitabine in dual combination with griseofulvin created increased levels of anti-neoplastic cytotoxicity that were greater than was attainable with gemcitabine-(C₄-amide)-[anti-HER2/neu] or gemcitabine alone.

Conclusion

Gemcitabine-(C₄-amide)-[anti-HER2/neu] in dual combination with griseofulvin can produce enhanced levels of anti-neoplastic cytotoxicity and potentially provide a basis for treatment regimens with a wider margin-of-safety. Such benefits would be possible through the collective properties of; [i] selective “targeted” gemcitabine delivery; [ii] relatively lower toxicity of griseofulvin compared to many if not most conventional chemotherapeutics; [iii] reduced total dosage requirements faciliated by additive or synergistic anti-cancer properties; and [iv] differences in sequelae for gemcitabine-(C₄-amide)-[anti-HER2/neu] compared to griseofulvin functioning as a tubulin/microtubule inhibitor.