Inhibition of Cdk2 kinase activity selectively targets the CD44⁺/CD24⁻/Low stem-like subpopulation and restores chemosensitivity of SUM149PT triple-negative breast cancer cells

Deciphering the molecular biology of inflammatory breast cancer through molecular characterization of patient samples and preclinical models

Inflammatory breast cancer is an aggressive subtype of breast cancer with dismal patient prognosis and a unique clinical presentation. In the past two decades, molecular profiling technologies have been used in order to gain insight into the molecular biology of IBC and to search for possible targets for treatment. Although a gene signature that accurately discriminates between IBC and nIBC patient samples and preclinical models was identified, the overall genomic and transcriptomic differences are small and ambiguous, mainly due to the limited sample sizes of the evaluated patient series and the failure to correct for confounding effects of the molecular subtypes. Nevertheless, data collected over the past 20 years by independent research groups increasingly support the existence of several IBC-specific biological characteristics. In this review, these features are classified as established, emerging and conceptual hallmarks based on the level of evidence reported in the literature. In addition, a synoptic model is proposed that integrates all hallmarks and that can explain how cancer cell intrinsic mechanisms (i.e. NF-κB activation, genomic instability, MYC-addiction, TGF-β resistance, adaptive stress response, chromatin remodeling, epithelial-to-mesenchymal transition) can contribute to the establishment of the dynamic immune microenvironment associated with IBC. It stands to reason that future research projects are needed to further refine (parts of) this model and to investigate its clinical translatability.

P129, a pyrazole ring-containing isolongifolanone-derivate: synthesis and investigation of anti-glioma action mechanism

BACKGROUND

Cyclin-dependent kinase-2 (CDK-2) is an important regulatory factor in the G1/S phase transition. CDK-2 targeting has been shown to suppress the viability of multiple cancers. However, the exploration and application of a CDK-2 inhibitor in the treatment of glioblastoma are sparse.

METHODS

We synthesized P129 based on isolongifolanone, a natural product with anti-tumor activity. Network pharmacology analysis was conducted to predict the structural stability, affinity, and pharmacological and toxicological properties of P129. Binding analysis and CETSA verified the ability of P129 to target CDK-2. The effect of P129 on the biological behavior of glioma cells was analyzed by the cell counting kit-8, colony formation, flow cytometry, and other experiments. Western blotting was used to detect the expression changes of proteins involved in the cell cycle, cell apoptosis, and epithelial-mesenchymal transition.

RESULTS

Bioinformatics analysis and CETSA showed that P129 exhibited good intestinal absorption and blood-brain barrier penetrability together with high stability and affinity with CDK-2, with no developmental toxicity. The viability, proliferation, and migration of human glioma cells were significantly inhibited by P129 in a dose- and time-dependent manner. Flow cytometry and western blotting analyses showed G0/G1 arrest and lower CDK-2 expression in cells treated with P129 than in the controls. The apoptotic ratio of glioma cells increased significantly with increasing concentrations of P129 combined with karyopyknosis and karyorrhexis. Apoptosis occurred via the mitochondrial pathway.

CONCLUSION

The pyrazole ring-containing isolongifolanone derivate P129 exhibited promising anti-glioma activity by targeting CDK-2 and promoting apoptosis, indicating its potential importance as a new chemotherapeutic option for glioma.

Molecular targets and therapeutic strategies for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is known for its heterogeneous complexity and is often difficult to treat. TNBC lacks the expression of major hormonal receptors like estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2 and is further subdivided into androgen receptor (AR) positive and AR negative. In contrast, AR negative is also known as quadruple-negative breast cancer (QNBC). Compared to AR-positive TNBC, QNBC has a great scarcity of prognostic biomarkers and therapeutic targets. QNBC shows excessive cellular growth and proliferation of tumor cells due to increased expression of growth factors like EGF and various surface proteins. This study briefly reviews the limited data available as protein biomarkers that can be used as molecular targets in treating TNBC as well as QNBC. Targeted therapy and immune checkpoint inhibitors have recently changed cancer treatment. Many studies in medicinal chemistry continue to focus on the synthesis of novel compounds to discover new antiproliferative medicines capable of treating TNBC despite the abundance of treatments currently on the market. Drug repurposing is one of the therapeutic methods for TNBC that has been examined. Moreover, some additional micronutrients, nutraceuticals, and functional foods may be able to lower cancer risk or slow the spread of malignant diseases that have already been diagnosed with cancer. Finally, nanomedicines, or applications of nanotechnology in medicine, introduce nanoparticles with variable chemistry and architecture for the treatment of cancer. This review emphasizes the most recent research on nutraceuticals, medication repositioning, and novel therapeutic strategies for the treatment of TNBC.

JAK-STAT Signaling in Inflammatory Breast Cancer Enables Chemotherapy-Resistant Cell States

Inflammatory breast cancer (IBC) is a difficult-to-treat disease with poor clinical outcomes due to high risk of metastasis and resistance to treatment. In breast cancer, CD44+CD24- cells possess stem cell-like features and contribute to disease progression, and we previously described a CD44+CD24-pSTAT3+ breast cancer cell subpopulation that is dependent on JAK2/STAT3 signaling. Here we report that CD44+CD24- cells are the most frequent cell type in IBC and are commonly pSTAT3+. Combination of JAK2/STAT3 inhibition with paclitaxel decreased IBC xenograft growth more than either agent alone. IBC cell lines resistant to paclitaxel and doxorubicin were developed and characterized to mimic therapeutic resistance in patients. Multi-omic profiling of parental and resistant cells revealed enrichment of genes associated with lineage identity and inflammation in chemotherapy-resistant derivatives. Integrated pSTAT3 chromatin immunoprecipitation sequencing and RNA sequencing (RNA-seq) analyses showed pSTAT3 regulates genes related to inflammation and epithelial-to-mesenchymal transition (EMT) in resistant cells, as well as PDE4A, a cAMP-specific phosphodiesterase. Metabolomic characterization identified elevated cAMP signaling and CREB as a candidate therapeutic target in IBC. Investigation of cellular dynamics and heterogeneity at the single cell level during chemotherapy and acquired resistance by CyTOF and single cell RNA-seq identified mechanisms of resistance including a shift from luminal to basal/mesenchymal cell states through selection for rare preexisting subpopulations or an acquired change. Finally, combination treatment with paclitaxel and JAK2/STAT3 inhibition prevented the emergence of the mesenchymal chemo-resistant subpopulation. These results provide mechanistic rational for combination of chemotherapy with inhibition of JAK2/STAT3 signaling as a more effective therapeutic strategy in IBC.

SIGNIFICANCE

Chemotherapy resistance in inflammatory breast cancer is driven by the JAK2/STAT3 pathway, in part via cAMP/PKA signaling and a cell state switch, which can be overcome using paclitaxel combined with JAK2 inhibitors.

CDK Inhibition Primes for Anti-PD-L1 Treatment in Triple-Negative Breast Cancer Models

Triple-negative breast cancers (TNBC) expressing PD-L1 qualify for checkpoint inhibitor immunotherapy. Cyclin E/CDK2 is a potential target axis in TNBC; however, small-molecule drugs at efficacious doses may be associated with toxicity, and treatment alongside immunotherapy requires investigation. We evaluated CDK inhibition at suboptimal levels and its anti-tumor and immunomodulatory effects. Transcriptomic analyses of primary breast cancers confirmed higher cyclin E/CDK2 expression in TNBC compared with non-TNBC. Out of the three CDK2-targeting inhibitors tested, the CDK 2, 7 and 9 inhibitor SNS-032 was the most potent in reducing TNBC cell viability and exerted cytotoxicity against all eight TNBC cell lines evaluated in vitro. Suboptimal SNS-032 dosing elevated cell surface PD-L1 expression in surviving TNBC cells. In mice engrafted with human immune cells and challenged with human MDA-MB-231 TNBC xenografts in mammary fat pads, suboptimal SNS-032 dosing partially restricted tumor growth, enhanced the tumor infiltration of human CD45⁺ immune cells and elevated cell surface PD-L1 expression in surviving cancer cells. In tumor-bearing mice engrafted with human immune cells, the anti-PD-L1 antibody avelumab, given sequentially following suboptimal SNS-032 dosing, reduced tumor growth compared with SNS-032 alone or with avelumab without prior SNS-032 priming. CDK inhibition at suboptimal doses promotes immune cell recruitment to tumors, PD-L1 expression by surviving TNBC cells and may complement immunotherapy.

Targeting protein kinases in cancer stem cells

Cancer stem cells (CSCs) are subpopulations of cancer cells within the tumor bulk that have emerged as an attractive therapeutic target for cancer therapy. Accumulating evidence has shown the critical involvement of protein kinase signaling pathways in driving tumor development, cancer relapse, metastasis, and therapeutic resistance. Given that protein kinases are druggable targets for cancer therapy, tremendous efforts are being made to target CSCs with kinase inhibitors. In this review, we summarize the current knowledge and overview of the roles of protein kinases in various signaling pathways in CSC regulation and drug resistance. Furthermore, we provide an update on the preclinical and clinical studies for the use of kinase inhibitors alone or in combination with current therapies for effective cancer therapy. Despite great premises for the use of kinase inhibitors against CSCs, further investigations are needed to evaluate their efficiencies without any adverse effects on normal stem cells.

Dinaciclib inhibits the stemness of two subtypes of human breast cancer cells by targeting the FoxM1 and Hedgehog signaling pathway

Cyclin‑dependent kinase (CDK)4/6 inhibitors in combination with endocrine therapy are the current standard of care used in the first‑line treatment of hormone receptor‑positive/HER2‑negative metastatic breast cancer (BC). Although CDK4/6 inhibitors mainly target the cell cycle, emerging evidence has indicated further potential roles of CDKs other than regulating cell cycle progression. The G₁ and G₂/M transition regulators, including cyclins D and E, as well as their catalytic partners, CDK2, CDK4 and CDK6, have been reported to play crucial roles in pluripotency maintenance and cell fate decisions of human pluripotent stem cells by controlling transcription factors, signaling pathways and epigenetic regulators. Dinaciclib, a CDK1/2/5/9 inhibitor, is currently being evaluated in clinical trials against various cancer types, including BC. However, the underlying molecular mechanisms of CDK1/2/5/9 inhibitors in regulating BC stemness remain poorly understood. The present study aimed to examine the stemness‑inhibitory effects of dinaciclib in MCF‑7 (luminal) and HCC‑1806 (triple‑negative) BC cells. We found that this drug not only effectively reduced the self‑renewal abilities and other malignant properties, but also dose‑dependently decreased the protein expression levels of three BC stem cell markers, CD44, aldehyde dehydrogenase 1 family member A1 (ALDH1A1) and BMI1 proto‑oncogene, polycomb ring finger (Bmi1), as well as three embryonic stem cell markers, Oct4, Nanog and Sox2. Moreover, the dinaciclib‑induced decrease of Oct4 and Nanog protein expression was able to be restored by co‑treatment with MG‑132, a proteasome inhibitor. Forkhead box M1 (FoxM1), both a stemness‑stimulating transcription factor and a cell cycle regulator, along with the Hedgehog signaling pathway, were identified as the therapeutic targets of dinaciclib. Collectively, the present results demonstrated a novel role of dinaciclib in suppressing BC stemness and indicated its potential use for future cancer treatments.

Development of Gene Expression-Based Random Forest Model for Predicting Neoadjuvant Chemotherapy Response in Triple-Negative Breast Cancer

Simple Summary

Only 20–50% of patients with triple negative breast cancer achieve a pathological complete response from neoadjuvant chemotherapy, a strong indicator of patient survival. Therefore, there is an urgent need for a reliable predictive model of the patient’s pathological complete response prior to actual treatment. The purpose of this study was to develop such a model based on random forest recursive feature elimination and to benchmark the performance of the proposed model against existing predictive models. Our study suggests that an 86-gene-based random forest model associated to DNA repair and cell cycle mechanisms can provide reliable predictions of neoadjuvant chemotherapy response in patients with triple negative breast cancer.

Abstract

Neoadjuvant chemotherapy (NAC) response is an important indicator of patient survival in triple negative breast cancer (TNBC), but predicting chemosensitivity remains a challenge in clinical practice. We developed an 86-gene-based random forest (RF) classifier capable of predicting neoadjuvant chemotherapy response (pathological Complete Response (pCR) or Residual Disease (RD)) in TNBC patients. The performance of pCR classification of the proposed model was evaluated by Receiver Operating Characteristic (ROC) curve and Precision Recall (PR) curve. The AUROC and AUPRC of the proposed model on the test set were 0.891 and 0.829, respectively. At a predefined specificity (>90%), the proposed model shows a superior sensitivity compared to the best performing reported NAC response prediction model (69.2% vs. 36.9%). Moreover, the predicted pCR status by the model well explains the distance recurrence free survival (DRFS) of TNBC patients. In addition, the pCR probabilities of the proposed model using the expression profiles of the CCLE TNBC cell lines show a high Spearman rank correlation with cyclophosphamide sensitivity in the TNBC cell lines (SRCC =0.697, p-value =0.031). Associations between the 86 genes and DNA repair/cell cycle mechanisms were provided through function enrichment analysis. Our study suggests that the random forest-based prediction model provides a reliable prediction of the clinical response to neoadjuvant chemotherapy and may explain chemosensitivity in TNBC.

MicroRNA-372-3p Predicts Response of TACE Patients Treated with Doxorubicin and Enhances Chemosensitivity in Hepatocellular Carcinoma

BACKGROUND

Identification of factors to detect and improve chemotherapy.response in cancer is the main concern. microRNA-372-3p (miR-372-3p) has been demonstrated to play a crucial role in cellular proliferation, apoptosis and metastasis of various cancers including Hepatocellular Carcinoma (HCC). However, its contribution towards Doxorubicin (Dox) chemosensitivity in HCC has never been studied.

OBJECTIVE

This study aims to investigate the potential role of miR-372-3p in enhancing Dox effects on HCC cell line (HepG2). Additionally, the correlation between miR-372-3p and HCC patients who received Transarterial Chemoembolization (TACE) with Dox treatment has been analyzed.

METHODS

Different cell processes were elucidated by cell viability, colony formation, apoptosis and wound healing assays after miR-372-3p transfection in HepG2 cells Furthermore, the miR-372-3p level has been estimated in the blood of primary HCC patients treated with TACE/Dox by quantitative real-time PCR assay. Receiver Operating Curve (ROC) analysis for serum miR-372-3p was constructed for its prognostic significance. Finally, the protein level of Mcl-1, the anti-apoptotic player, has been evaluated using western blot.

RESULTS

We found a significantly higher level of miR-372-3p in the blood of the responder group of HCC patients who received TACE with Dox than of non-responders. Ectopic expression of miR-372-3p reduced cell proliferation, migration and significantly induced apoptosis in HepG2 cells which was coupled with a decrease of anti-apoptotic protein Mcl-1.

CONCLUSION

Our study demonstrated that miR-372-3p acts as a tumor suppressor in HCC and can act as a predictor biomarker for drug response. Furthermore, the data referred for the first time its potential role in drug sensitivity that might be a therapeutic target for HCC.

Aurora-A kinase oncogenic signaling mediates TGF-β-induced triple-negative breast cancer plasticity and chemoresistance

Triple-negative breast cancer (TNBCs) account for 15–20% of all breast cancers and represent the most aggressive subtype of this malignancy. Early tumor relapse and progression are linked to the enrichment of a sub-fraction of cancer cells, termed breast tumor-initiating cells (BTICs), that undergo epithelial to mesenchymal transition (EMT) and typically exhibit a basal-like CD44^high/CD24^low and/or ALDH1^high phenotype with critical cancer stem-like features such as high self-renewal capacity and intrinsic (de novo) resistance to standard of care chemotherapy. One of the major mechanisms responsible for the intrinsic drug resistance of BTICs is their high ALDH1 activity leading to inhibition of chemotherapy-induced apoptosis. In this study, we demonstrated that aurora-A kinase (AURKA) is required to mediate TGF-β-induced expression of the SNAI1 gene, enrichment of ALDH1^high BTICs, self-renewal capacity, and chemoresistance in TNBC experimental models. Significantly, the combination of docetaxel (DTX) with dual TGF-β and AURKA pharmacologic targeting impaired tumor relapse and the emergence of distant metastasis. We also showed in unique chemoresistant TNBC cells isolated from patient-derived TNBC brain metastasis that dual TGF-β and AURKA pharmacologic targeting reversed cancer plasticity and enhanced the sensitivity of TNBC cells to DTX-based-chemotherapy. Taken together, these findings reveal for the first time the critical role of AURKA oncogenic signaling in mediating TGF-β-induced TNBC plasticity, chemoresistance, and tumor progression.

MicroRNA-424-5p enhances chemosensitivity of breast cancer cells to Taxol and regulates cell cycle, apoptosis, and proliferation

Combination therapy has been considered as a potential method to overcome the BC chemoresistance. MicroRNAs (miRs) have been suggested as a therapeutic factor in the combination therapy of BC. This project aimed at examining the possible activity and molecular function of miR-424-5p and Taxol combination in the human BC cell line. MDA-MB-231 cells were treated with miR-424-5p mimics and Taxol, in a combined manner or separately. We used the MTT test for assessing the cell proliferation. In addition, flow-cytometry was used for evaluating apoptosis and cell-cycle. Expression levels of underlying molecular factors of miR-424-5p were assessed using western-blotting and qRT-PCR. The obtained results demonstrated that miR-424-5p repressed BC cell proliferation and sensitized these cells to Taxol treatment through the induction of apoptosis. Further investigations showed that miR-424-5p might increase BC chemosensitivity through the regulation of apoptosis-related factors including P53, Caspase-3, Bcl-2, and Bax as well as the proliferation-related gene c-Myc. Moreover, miR-424-5p restoration in combination with Taxol treatment decreased the colony formation by regulating Oct-4 and led to G2 arrest via modulating Cdk-2 expression. Western-blotting demonstrated that miR-424-5p may perform its anti-chemoresistance role by regulating the PD-L1 expression and controlling PTEN/PI3K/AKT/mTOR. Overall, the upregulation of miR-424-5p was indicated to upregulate the sensitivity of BC cells to treatment with Taxol. MiR-424-5p might regulate the chemosensitivity of the BC cell line by modulating PD-L1 and controlling the PTEN/mTOR axis. Therefore, the combination of miR-424-5p with Taxol would represent a novel procedure to treat against BC.

Activity-Based Protein Profiling Reveals Potential Dasatinib Targets in Gastric Cancer

Dasatinib is a multi-target kinase inhibitor, whose targets include BCR-ABL, SRC family kinases, and various cancer kinases. The elevated SRC activity in gastric cancer (GC) has prompted the need for the therapeutic application of dasatinib in GC. We observed that the efficacy of dasatinib varied with the GC cell lines. The differential effect of dasatinib was not correlated with the basal SRC activity of each cell line. Moreover, the GC cell lines showing the strong antitumor effects of dasatinib were refractory to other SRC inhibitors, i.e., bosutinib and saracatinib, suggesting that unexpected dasatinib’s targets could exist. To profile the targets of dasatinib in GC, we performed activity-based protein profiling (ABPP) via mass spectrometry using a desthiobiotin-ATP probe. We identified 29 and 18 kinases as potential targets in dasatinib-sensitive (SNU-216, MKN-1) and -resistant (SNU-484, SNU-601) cell lines, respectively. The protein–protein interaction mapping of the differential drug targets in dasatinib-sensitive and -resistant GC using the STRING database suggested that dasatinib could target cellular energy homeostasis in the drug-sensitive GC. RNAi screening for identified targets indicated p90RSK could be a novel dasatinib target, which is important for maintaining the viability and motility of GC cells. Further functional validation of dasatinib off-target actions will provide more effective therapeutic options for GC.

Biomarkers in Triple-Negative Breast Cancer: State-of-the-Art and Future Perspectives

Triple-negative breast cancer (TNBC) is a heterogeneous group of tumors characterized by aggressive behavior, high risk of distant recurrence, and poor survival. Chemotherapy is still the main therapeutic approach for this subgroup of patients, therefore, progress in the treatment of TNBC remains an important challenge. Data derived from molecular technologies have identified TNBCs with different gene expression and mutation profiles that may help developing targeted therapies. So far, however, only a few of these have shown to improve the prognosis and outcomes of TNBC patients. Robust predictive biomarkers to accelerate clinical progress are needed. Herein, we review prognostic and predictive biomarkers in TNBC, discuss the current evidence supporting their use, and look at the future of this research field.

Targeting CDK2 in cancer: challenges and opportunities for therapy

Cyclin-dependent kinase 2 (CDK2) plays a pivotal part in cell cycle regulation and is involved in a range of biological processes. CDK2 interacts with and phosphorylates proteins in pathways such as DNA damage, intracellular transport, protein degradation, signal transduction, DNA and RNA metabolism and translation. CDK2 and its regulatory subunits are deregulated in many human cancers and there is emerging evidence suggesting CDK2 inhibition elicits antitumor activity in a subset of tumors with defined genetic features. Previous CDK2 inhibitors were nonspecific and limited by off-target effects. The development of new-generation CDK2 inhibitors represents a therapeutic opportunity for CDK2-dependent cancers.

Goniolanceolatins A-H, Cytotoxic Bis-styryllactones from Goniothalamus lanceolatus

Eight new bis-styryllactones, goniolanceolatins A-H (1-8), possessing a rare α,β-unsaturated δ-lactone moiety with a (6S)-configuration, were isolated from the CH₂Cl₂ extract of the stembark and roots of Goniothalamus lanceolatus Miq., a plant endemic to Malaysia. Absolute structures were established through extensive 1D- and 2D-NMR data analysis, in combination with electronic dichroism (ECD) data. All of the isolates were evaluated for their cytotoxicity against human lung and colorectal cancer cell lines. Compounds 2 and 4 showed cytotoxicity, with IC₅₀ values ranging from 2.3 to 4.2 μM, and were inactive toward human noncancerous lung and colorectal cells. Compounds 1, 3, 6, 7, and 8 showed moderate to weak cytotoxicity. Docking studies of compounds 2 and 4 showed that they bind with EGFR tyrosine kinase and cyclin-dependent kinase 2 through hydrogen bonding interactions with the important amino acids, including Lys721, Met769, Asn818, Arg157, Ile10, and Glu12.

To control or to be controlled? Dual roles of CDK2 in DNA damage and DNA damage response

CDK2 (cyclin-dependent kinase 2), a member of the CDK family, has been shown to play a role in many cellular activities including cell cycle progression, apoptosis and senescence. Recently, accumulating evidence indicates that CDK2 is involved in DNA damage and DNA repair response (DDR). When DNA is damaged by internal or external genotoxic stresses, CDK2 activity is required for proper DNA repair in vivo and in vitro, whereas inactivation of CDK2 by siRNA techniques or by inhibitors could result in DNA damage and stimulate DDR. Hence, CDK2 seems to play dual roles in DNA damage and DDR. On one aspect, it is activated and stimulates DDR to repair DNA damage when DNA damage occurs; on the other hand, its inactivation directly leads to DNA damage and evokes DDR. Here, we describe the roles of CDK2 in DNA damage and DDR, and discuss the potential application of CDK2 inhibitors as anti-cancer agents.

Norcantharidin regulates ERα signaling and tamoxifen resistance via targeting miR-873/CDK3 in breast cancer cells

MiR-873/CDK3 has been shown to play a critical role in ERα signaling and tamoxifen resistance. Thus, targeting this pathway may be a potential therapeutic approach for the treatment of ER positive breast cancer especially tamoxifen resistant subtype. Here we report that Norcantharidin (NCTD), currently used clinically as an ani-cancer drug in China, regulates miR-873/CDK3 axis in breast cancer cells. NCTD decreases the transcriptional activity of ERα but not ERβ through the modulation of miR-873/CDK3 axis. We also found that NCTD inhibits cell proliferation and tumor growth and miR-873/CDK3 axis mediates cell proliferation suppression of NCTD. More important, we found that NCTD sensitizes resistant cells to tamoxifen. NCTD inhibits tamoxifen induced the transcriptional activity as well ERα downstream gene expressions in tamoxifen resistant breast cancer cells. In addition, we found that NCTD restores tamoxifen induced recruitments of ERα co-repressors N-CoR and SMRT. Knockdown of miR-873 and overexpression of CDK3 diminish the effect of NCTD on tamoxifen resistance. Our data shows that NCTD regulates ERα signaling and tamoxifen resistance by targeting miR-873/CDK3 axis in breast cancer cells. This study may provide an alternative therapy strategy for tamoxifen resistant breast cancer.

NOTCH3 expression is linked to breast cancer seeding and distant metastasis

Background

Development of distant metastases involves a complex multistep biological process termed the invasion-metastasis cascade, which includes dissemination of cancer cells from the primary tumor to secondary organs. NOTCH developmental signaling plays a critical role in promoting epithelial-to-mesenchymal transition, tumor stemness, and metastasis. Although all four NOTCH receptors show oncogenic properties, the unique role of each of these receptors in the sequential stepwise events that typify the invasion-metastasis cascade remains elusive.

Methods

We have established metastatic xenografts expressing high endogenous levels of NOTCH3 using estrogen receptor alpha-positive (ERα⁺) MCF-7 breast cancer cells with constitutive active Raf-1/mitogen-associated protein kinase (MAPK) signaling (vMCF-7^Raf-1) and MDA-MB-231 triple-negative breast cancer (TNBC) cells. The critical role of NOTCH3 in inducing an invasive phenotype and poor outcome was corroborated in unique TNBC cells resulting from a patient-derived brain metastasis (TNBC-M25) and in publicly available claudin-low breast tumor specimens collected from participants in the Molecular Taxonomy of Breast Cancer International Consortium database.

Results

In this study, we identified an association between NOTCH3 expression and development of metastases in ERα⁺ and TNBC models. ERα⁺ breast tumor xenografts with a constitutive active Raf-1/MAPK signaling developed spontaneous lung metastases through the clonal expansion of cancer cells expressing a NOTCH3 reprogramming network. Abrogation of NOTCH3 expression significantly reduced the self-renewal and invasive capacity of ex vivo breast cancer cells, restoring a luminal CD44^low/CD24^high/ERα^high phenotype. Forced expression of the mitotic Aurora kinase A (AURKA), which promotes breast cancer metastases, failed to restore the invasive capacity of NOTCH3-null cells, demonstrating that NOTCH3 expression is required for an invasive phenotype. Likewise, pharmacologic inhibition of NOTCH signaling also impaired TNBC cell seeding and metastatic growth. Significantly, the role of aberrant NOTCH3 expression in promoting tumor self-renewal, invasiveness, and poor outcome was corroborated in unique TNBC cells from a patient-derived brain metastasis and in publicly available claudin-low breast tumor specimens.

Conclusions

These findings demonstrate the key role of NOTCH3 oncogenic signaling in the genesis of breast cancer metastasis and provide a compelling preclinical rationale for the design of novel therapeutic strategies that will selectively target NOTCH3 to halt metastatic seeding and to improve the clinical outcomes of patients with breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-1020-0) contains supplementary material, which is available to authorized users.

A Metabolomic Approach to Predict Breast Cancer Behavior and Chemotherapy Response

Although the classification of breast carcinomas into molecular or immunohistochemical subtypes has contributed to a better categorization of women into different therapeutic regimens, breast cancer nevertheless still progresses or recurs in a remarkable number of patients. Identifying women who would benefit from chemotherapy could potentially increase treatment effectiveness, which has important implications for long-term survival. Metabolomic analyses of fluids and tissues from cancer patients improve our knowledge of the reprogramming of metabolic pathways involved in resistance to chemotherapy. This review evaluates how recent metabolomic approaches have contributed to understanding the relationship between breast cancer and the acquisition of resistance. We focus on the advantages and challenges of cancer treatment and the use of new strategies in clinical care, which helps us comprehend drug resistance and predict responses to treatment.

Cyclin E overexpression as a biomarker for combination treatment strategies in inflammatory breast cancer

Inflammatory breast cancer (IBC) is a virulent form of breast cancer, and novel treatment strategies are urgently needed. Immunohistochemical analysis of tumors from women with a clinical diagnosis of IBC (n = 147) and those with non-IBC breast cancer (n = 2510) revealed that, whereas in non-IBC cases cytoplasmic cyclin E was highly correlated with poor prognosis (P < 0.001), in IBC cases both nuclear and cytoplasmic cyclin E were indicative of poor prognosis. These results underscored the utility of the cyclin E/CDK2 complex as a novel target for treatment. Because IBC cell lines were highly sensitive to the CDK2 inhibitors dinaciclib and meriolin 5, we developed a high-throughput survival assay (HTSA) to design novel sequential combination strategies based on the presence of cyclin E and CDK2. Using a 14-cell-line panel, we found that dinaciclib potentiated the activity of DNA-damaging chemotherapies treated in a sequence of dinaciclib followed by chemotherapy, whereas this was not true for paclitaxel. We also identified a signature of DNA repair–related genes that are downregulated by dinaciclib, suggesting that global DNA repair is inhibited and that prolonged DNA damage leads to apoptosis. Taken together, our findings argue that CDK2-targeted combinations may be viable strategies in IBC worthy of future clinical investigation.

Transforming doxorubicin into a cancer stem cell killer via EpCAM aptamer-mediated delivery

Chemotherapy-resistant cancer stem cells (CSCs) are a major obstacle to the effective treatment of many forms of cancer. To overcome CSC chemo-resistance, we developed a novel system by conjugating a CSC-targeting EpCAM aptamer with doxorubicin (Apt-DOX) to eliminate CSCs. Incubation of Apt-DOX with colorectal cancer cells resulted in high concentration and prolonged retention of DOX in the nuclei. Treatment of tumour-bearing xenograft mice with Apt-DOX resulted in at least 3-fold more inhibition of tumour growth and longer survival as well as a 30-fold lower frequency of CSC and a prolonged longer tumourigenic latency compared with those receiving the same dose of free DOX. Our data demonstrate that a CSC-targeting aptamer is able to transform a conventional chemotherapeutic agent into a CSC-killer to overcome drug resistance in solid tumours.

Targeting long non-coding RNA DANCR inhibits triple negative breast cancer progression

Triple negative breast cancer (TNBC) is non-responsive to conventional anti-hormonal and Her2-targeted therapies, making it necessary to identify new molecular targets for therapy. Long non-coding RNA anti-differentiation ncRNA (lncRNA DANCR) was identified participating in carcinogenesis of hepatocellular carcinoma, but its expression and potential role in TNBC progression is still unclear. In the present study, our results showed that DANCR expression was increased in TNBC tissues compared with the adjacent normal tissues using quantitative real-time PCR (qRT-PCR) in 63 TNBC specimens. Patients with higher DANCR expression correlated with worse TNM stages as well as a shorter overall survival (OS) using Kaplan–Meier analysis. When the endogenous DANCR was knocked-down via specific siRNA, cell proliferation and invasion were decreased obviously in the MDA-MB-231 cells. In vivo xenograft experiments showed that knockdown of the DANCR in MDA-MB-231 cells reduced the tumor growth significantly. Furthermore, a compendium of TNBC cancer stem cell markers such as CD44, ABCG2 transporter and aldehyde dehydrogenase (ALDH1) were greatly downregulated in the MDA-MB-231 cells with DANCR knockdown. Molecular mechanistic studies revealed that knockdown of DANCR was associated with increased binding of EZH2 on the promoters of CD44 and ABCG2, and concomitant reduction of expression of these genes suggested that they may be DANCR targets in TNBC. Thus, our study demonstrated that targeting DANCR expression might be a viable therapeutic approach to treat triple negative breast cancer.

Summary: Targeting LncRNA DANCR obstructs triple negative breast cancer progression by down-regulating cancer stem cell marker CD44 and ABCG2.

Molecular targeting of the Aurora-A/SMAD5 oncogenic axis restores chemosensitivity in human breast cancer cells

Although the majority of breast cancers initially respond to the cytotoxic effects of chemotherapeutic agents, most breast cancer patients experience tumor relapse and ultimately die because of drug resistance. Breast cancer cells undergoing epithelial to mesenchymal transition (EMT) acquire a CD44⁺/CD24^-/ALDH1⁺ cancer stem cell-like phenotype characterized by an increased capacity for tumor self-renewal, intrinsic drug resistance and high proclivity to develop distant metastases. We uncovered in human breast tumor xenografts a novel non-mitotic role of Aurora-A kinase in promoting breast cancer metastases through activation of EMT and expansion of breast tumor initiating cells (BTICs). In this study we characterized the role of the Aurora-A/SMAD5 oncogenic axis in the induction of chemoresistance. Breast cancer cells overexpressing Aurora-A showed resistance to conventional chemotherapeutic agents, while treatment with alisertib, a selective Aurora-A kinase inhibitor, restored chemosensitivity. Significantly, SMAD5 expression was required to induce chemoresistance and maintain a breast cancer stem cell-like phenotype, indicating that the Aurora-A/SMAD5 oncogenic axis promotes chemoresistance through activation of stemness signaling. Taken together, these findings identified a novel mechanism of drug resistance through aberrant activation of the non-canonical Aurora-A/SMAD5 oncogenic axis in breast cancer.

Centrosome amplification: a suspect in breast cancer and racial disparities

The multifaceted involvement of centrosome amplification (CA) in tumorigenesis is coming into focus following years of meticulous experimentation, which have elucidated the powerful abilities of CA to promote cellular invasion, disrupt stem cell division, drive chromosomal instability (CIN) and perturb tissue architecture, activities that can accelerate tumor progression. Integration of the extant in vitro, in vivo and clinical data suggests that in some tissues CA may be a tumor-initiating event, in others a consequential 'hit' in multistep tumorigenesis, and in some others, non-tumorigenic. However, in vivo data are limited and primarily focus on PLK4 (which has CA-independent mechanisms by which it promotes aggressive cellular phenotypes). In vitro breast cancer models suggest that CA can promote tumorigenesis in breast cancer cells in the setting of p53 loss or mutation, which can both trigger CA and promote cellular tolerance to its tendency to slow proliferation and induce aneuploidy. It is thus our perspective that CA is likely an early hit in multistep breast tumorigenesis that may sometimes be lost to preserve aggressive karyotypes acquired through centrosome clustering-mediated CIN, both numerical and structural. We also envision that the robust link between p53 and CA may underlie, to a considerable degree, racial health disparity in breast cancer outcomes. This question is clinically significant because, if it is true, then analysis of centrosomal profiles and administration of centrosome declustering drugs could prove highly efficacious in risk stratifying breast cancers and treating African American (AA) women with breast cancer.

HER2 in Breast Cancer Stemness: A Negative Feedback Loop towards Trastuzumab Resistance

HER2 receptor tyrosine kinase that is overexpressed in approximately 20% of all breast cancers (BCs) is a poor prognosis factor and a precious target for BC therapy. Trastuzumab is approved by FDA to specifically target HER2 for treating HER2+ BC. However, about 60% of patients with HER2+ breast tumor develop de novo resistance to trastuzumab, partially due to the loss of expression of HER2 extracellular domain on their tumor cells. This is due to shedding/cleavage of HER2 by metalloproteinases (ADAMs and MMPs). HER2 shedding results in the accumulation of intracellular carboxyl-terminal HER2 (p95HER2), which is a common phenomenon in trastuzumab-resistant tumors and is suggested as a predictive marker for trastuzumab resistance. Up-regulation of the metalloproteinases is a poor prognosis factor and is commonly seen in mesenchymal-like cancer stem cells that are risen during epithelial to mesenchymal transition (EMT) of tumor cells. HER2 cleavage during EMT can explain why secondary metastatic tumors with high percentage of mesenchymal-like cancer stem cells are mostly resistant to trastuzumab but still sensitive to lapatinib. Importantly, many studies report HER2 interaction with oncogenic/stemness signaling pathways including TGF-β/Smad, Wnt/β-catenin, Notch, JAK/STAT and Hedgehog. HER2 overexpression promotes EMT and the emergence of cancer stem cell properties in BC. Increased expression and activation of metalloproteinases during EMT leads to proteolytic cleavage and shedding of HER2 receptor, which downregulates HER2 extracellular domain and eventually increases trastuzumab resistance. Here, we review the hypothesis that a negative feedback loop between HER2 and stemness signaling drives resistance of BC to trastuzumab.

The Consequences of Chromosome Segregation Errors in Mitosis and Meiosis

Mistakes during cell division frequently generate changes in chromosome content, producing aneuploid or polyploid progeny cells. Polyploid cells may then undergo abnormal division to generate aneuploid cells. Chromosome segregation errors may also involve fragments of whole chromosomes. A major consequence of segregation defects is change in the relative dosage of products from genes located on the missegregated chromosomes. Abnormal expression of transcriptional regulators can also impact genes on the properly segregated chromosomes. The consequences of these perturbations in gene expression depend on the specific chromosomes affected and on the interplay of the aneuploid phenotype with the environment. Most often, these novel chromosome distributions are detrimental to the health and survival of the organism. However, in a changed environment, alterations in gene copy number may generate a more highly adapted phenotype. Chromosome segregation errors also have important implications in human health. They may promote drug resistance in pathogenic microorganisms. In cancer cells, they are a source for genetic and phenotypic variability that may select for populations with increased malignance and resistance to therapy. Lastly, chromosome segregation errors during gamete formation in meiosis are a primary cause of human birth defects and infertility. This review describes the consequences of mitotic and meiotic errors focusing on novel concepts and human health.

Expression and functionality of TRPV1 in breast cancer cells

Transient receptor potential (TRP) channels contribute to the regulation of intracellular calcium, which can promote cancer hallmarks in cases of dysregulation of gene transcription and calcium-dependent pro-proliferative or anti-apoptotic mechanisms. Several studies have begun to elucidate the roles of TRPV1, TRPV6, TRPM8, and TRPC1 in cancer progression; however, no study has examined the expression profiles of human TRP channels in breast cancer on a large scale. This study focused on the expression and functionality of TRPV1, a nonselective cation channel that was found to be expressed in different carcinoma tissues. Next-generation sequencing analyses revealed the expression of TRPV1 in several native breast cancer tissues, which was subsequently validated via reverse transcriptase-polymerase chain reaction. Activation of TRPV1 by its ligand capsaicin was associated with the growth inhibition of some cancer cell types; however, the signaling components involved are complex. In this study, stimulation by the TRPV1 agonist, capsaicin, of SUM149PT cells, a model system for the most aggressive breast cancer subtype, triple-negative breast cancer, led to intracellular calcium signals that were diminished by the specific TRPV1 antagonist, capsazepin. Activation of TRPV1 by capsaicin caused significant inhibition of cancer cell growth and induced apoptosis and necrosis. In conclusion, the current study revealed the expression profiles of human TRP channels in 60 different breast cancer tissues and cell lines and furthermore validated the antitumor activity of TRPV1 against SUM149PT breast cancer cells, indicating that activation of TRPV1 could be used as a therapeutic target, even in the most aggressive breast cancer types.

Both bulk and cancer stem cell subpopulations in triple-negative breast cancer are susceptible to Wnt, HDAC, and ERα coinhibition

Development of targeted therapies for triple-negative breast cancer (TNBC, a more aggressive subtype) is an unmet medical need. We analyzed data from 887 patients with invasive breast cancer and observed that increased Wnt and histone deacetylase (HDAC) activities are associated with estrogen receptor 1 (ESR1) and progesterone receptor (PGR) repression, poor survival, and increased relapse. The inverse correlation between Wnt signaling and repression of ESR1 and PGR expression was found to be magnified in cancer stem cell (CSC) subpopulations in TNBC cell lines. Cosuppression of Wnt, HDAC, and ESR1 using clinically relevant low-dose inhibitors effectively repressed both bulk and CSC subpopulations and converted CSCs to non-CSCs in TNBC cells without affecting MCF-10A mammary epithelial cells.

Cyclin-Dependent Kinase 2 Promotes Tumor Proliferation and Induces Radio Resistance in Glioblastoma

Accumulating evidence indicates that CDK2 promotes hyperproliferation and is associated to poor prognosis in multiple cancer cells. However, the physiological role of CDK2 in GBM and the biological mechanism still remains unclear. In this study, we identified that CDK2 expression was significantly enriched in GBM tumors compared with normal brain. Additionally, CDK2 was functionally required for tumor proliferation and its expression was associated to poor prognosis in GBM patients. Mechanically, CDK2 induced radio resistance in GBM cells and CDK2 knock down increased cell apoptosis when combined with radiotherapy. Therapeutically, we found that CDK2 inhibitor attenuated tumor growth both in vitro and in vivo. Collectively, CDK2 promotes proliferation, induces radio resistance in GBM, and could become a therapeutic target for GBM.

Roles and targeting of the HAS/hyaluronan/CD44 molecular system in cancer

Synthesis, deposition, and interactions of hyaluronan (HA) with its cellular receptor CD44 are crucial events that regulate the onset and progression of tumors. The intracellular signaling pathways initiated by HA interactions with CD44 leading to tumorigenic responses are complex. Moreover, HA molecules may perform dual functions depending on their concentration and size. Overexpression of variant isoforms of CD44 (CD44v) is most commonly linked to cancer progression, whereas their loss is associated with inhibition of tumor growth. In this review, we highlight that the regulation of HA synthases (HASes) by post-translational modifications, such as O-GlcNAcylation and ubiquitination, environmental factors and the action of microRNAs is important for HA synthesis and secretion in the tumor microenvironment. Moreover, we focus on the roles and interactions of CD44 with various proteins that reside extra- and intracellularly, as well as on cellular membranes with particular reference to the CD44-HA axis in cancer stem cell functions, and the importance of CD44/CD44v6 targeting to inhibit tumorigenesis.

A Novel High-Throughput 3D Screening System for EMT Inhibitors: A Pilot Screening Discovered the EMT Inhibitory Activity of CDK2 Inhibitor SU9516

Epithelial-mesenchymal transition (EMT) is a crucial pathological event in cancer, particularly in tumor cell budding and metastasis. Therefore, control of EMT can represent a novel therapeutic strategy in cancer. Here, we introduce an innovative three-dimensional (3D) high-throughput screening (HTS) system that leads to an identification of EMT inhibitors. For the establishment of the novel 3D-HTS system, we chose NanoCulture Plates (NCP) that provided a gel-free micro-patterned scaffold for cells and were independent of other spheroid formation systems using soft-agar. In the NCP-based 3D cell culture system, A549 lung cancer cells migrated, gathered, and then formed multiple spheroids within 7 days. Live cell imaging experiments showed that an established EMT-inducer TGF-β promoted peripheral cells around the core of spheroids to acquire mesenchymal spindle shapes, loss of intercellular adhesion, and migration from the spheroids. Along with such morphological change, EMT-related gene expression signatures were altered, particularly alteration of mRNA levels of ECAD/CDH1, NCAD/CDH2, VIM and ZEB1/TCF8. These EMT-related phenotypic changes were blocked by SB431542, a TGF-βreceptor I (TGFβR1) inhibitor. Inside of the spheroids were highly hypoxic; in contrast, spheroid-derived peripheral migrating cells were normoxic, revealed by visualization and quantification using Hypoxia Probe. Thus, TGF-β-triggered EMT caused spheroid hypoplasia and loss of hypoxia. Spheroid EMT inhibitory (SEMTIN) activity of SB431542 was calculated from fluorescence intensities of the Hypoxia Probe, and then was utilized in a drug screening of EMT-inhibitory small molecule compounds. In a pilot screening, 9 of 1,330 compounds were above the thresholds of the SEMTIN activity and cell viability. Finally, two compounds SB-525334 and SU9516 showed SEMTIN activities in a dose dependent manner. SB-525334 was a known TGFβR1 inhibitor. SU9516 was a cyclin-dependent kinase 2 (CDK2) inhibitor, which we showed also had an EMT-inhibitory activity. The half maximal inhibitory concentration (IC₅₀) of SB-525334 and SU9516 were 0.31 μM and 1.21 μM, respectively, while IC₅₀ of SB431542 was 2.38 μM. Taken together, it was shown that this 3D NCP-based HTS system was useful for screening of EMT-regulatory drugs.

Genome-wide profiling of long non-coding RNA expression patterns in anthracycline-resistant breast cancer cells

Long non-coding RNAs (lncRNAs) are involved in cancer progression. In the present study, we analyzed the lncRNA profiles in adriamycin-resistant and -sensitive breast cancer cells and found a group of dysregulated lncRNAs in the adriamycin-resistant cells. Expression of the dysregulated lncRNAs was correlated with dysregulated mRNAs, and these were enriched in GO and KEGG pathways associated with cancer progression and chemoresistance development. Among these lncRNA-mRNA interactions, some lncRNAs may cis‑regulate neighboring protein-coding genes and be involved in chemoresistance. We then validated that the lncRNA NONHSAT028712 regulated nearby CDK2 and interfered with the cell cycle and chemoresistance. Furthermore, we identified another group of lncRNAs that trans-regulated genes by interacting with different transcription factors. For example, NONHSAT057282 and NONHSAG023333 modulated chemoresistance and most likely interacted with the transcription factors ELF1 and E2F1, respectively. In conclusion, in the present study, we report for the first time the lncRNA expression patterns in adriamycin-resistant breast cancer cells, and provide a group of novel lncRNA targets that mediate chemoresistance development in both cis- and trans-action modes.

CD44 correlates with clinicopathological characteristics and is upregulated by EGFR in breast cancer

Cluster of differentiation 44 (CD44), a well-known transmembrane glycoprotein, serves as a promoting factor in the carcinogenesis and progression of a variety of neoplasms. Previous studies have demonstrated that aberrant expression of CD44 was associated with the initiation, invasion, metastasis, and therapy-resistance of breast cancer, but whether there was any association between CD44 and pathological characteristics of breast cancer or epidermal growth factor receptor (EGFR) has not been clearly elucidated. In this study, we utilized public microarray data analysis and tissue microarray technologies to display that CD44 level was enhanced in breast cancer and was significantly correlated with histological grade and the status of estrogen receptor, progesterone receptor and human epidermal growth factor receptor-2 (HER2) and EGFR. Furthermore, mRNA expression of CD44 in breast tumors was positively correlated with basal cytokeratin markers KRT5 and KRT17, but inversely associated with luminal marker FOXA1. Besides, Kaplan-Meier analysis showed that high CD44 mRNA level had adverse impact on the progression-free survival of patients with HER2-expressing or basal-like breast cancer. Functionally, inhibition of EGFR activity by erlotinib impaired the invasion and migration ability of breast cancer cell lines. Western blot assays demonstrated that erlotinib treatment decreased the expression of CD44, accompanied with the reduced protein levels of mesenchymal and cancer stem cell markers. Collectively, this study suggested that the expression of CD44 was upregulated by EGFR pathway and CD44 had a robust impact on the development of breast cancer.

Targeting miR-381-NEFL axis sensitizes glioblastoma cells to temozolomide by regulating stemness factors and multidrug resistance factors

MicroRNA-381 (miR-381) is a highly expressed onco-miRNA that is involved in malignant progression and has been suggested to be a good target for glioblastoma multiforme (GBM) therapy. In this study, we employed two-dimensional fluorescence differential gel electrophoresis (2-D DIGE) and MALDI–TOF/TOF-MS/MS to identify 27 differentially expressed proteins, including the significantly upregulated neurofilament light polypeptide (NEFL), in glioblastoma cells in which miR-381 expression was inhibited. We identified NEFL as a novel target molecule of miR-381 and a tumor suppressor gene. In human astrocytoma clinical specimens, NEFL was downregulated with increased levels of miR-381 expression. Either suppressing miR-381 or enforcing NEFL expression dramatically sensitized glioblastoma cells to temozolomide (TMZ), a promising chemotherapeutic agent for treating GBMs. The mechanism by which these cells were sensitized to TMZ was investigated by inhibiting various multidrug resistance factors (ABCG2, ABCC3, and ABCC5) and stemness factors (ALDH1, CD44, CKIT, KLF4, Nanog, Nestin, and SOX2). Our results further demonstrated that miR-381 overexpression reversed the viability of U251 cells exhibiting NEFL-mediated TMZ sensitivity. In addition, NEFL-siRNA also reversed the proliferation rate of U251 cells exhibiting locked nucleic acid (LNA)-anti-miR-381-mediated TMZ sensitivity. Overall, the miR-381-NEFL axis is important for TMZ resistance in GBM and may potentially serve as a novel therapeutic target for glioma.

Cripto-1: an extracellular protein - connecting the sequestered biological dots

Cripto-1 (CR-1) is a multifunctional embryonic protein that is re-expressed during inflammation, wound repair, and malignant transformation. CR-1 can function either as a tethered co-receptor or shed as a free ligand underpinning its flexible role in cell physiology. CR-1 has been shown to mediate cell growth, migration, invasion, and induce epithelial to mesenchymal transition (EMT). The main signaling pathways mediating CR-1 effects include Nodal-dependent (Smad2/3) and Nodal-independent (Src/p44/42/Akt) signaling transduction pathways. In addition, there are several naturally occurring binding partner proteins (BPPs) for CR-1 that can either agonize or antagonize its bioactivity. We will review the collective role of CR-1 as an extracellular protein, discuss caveats to consider in developing a quantitation assay, define possible mechanistic avenues applicable for drug discovery, and report on our experimental approaches to overcome these problematic issues.

Basal Protein Expression Is Associated With Worse Outcome and Trastuzamab Resistance in HER2+ Invasive Breast Cancer

BACKGROUND

We investigated the effect of basal protein expression on trastuzamab response in patients with HER2-positive (HER2(+)) breast cancer who received trastuzamab (T) and in HER2(+) breast cancer cell lines.

PATIENTS AND METHODS

Expression of cytokeratin (CK) 5/6, CK14, and epidermal growth factor receptor (EGFR) was evaluated after immunohistochemical staining in paraffin-embedded tissue of 97 patients with stage I to III HER2(+) breast cancer treated with chemotherapy/T. Groups with and without basal protein expression were compared with respect to clinicopathologic parameters and survival. We treated 4 cell lines (2 basal-HER2 [HCC1569, HCC1954] and 2 nonbasal HER2 [BT474, SKBR3]) each with vehicle, T 20 μg/mL, paclitaxel 0.01 μM (P), and T with P (T + P). Cell viability was assessed and HER2 pathway suppression was compared between groups using immunoblot analysis. Mammosphere formation was used to assess breast cancer stem cell properties.

RESULTS

EGFR expression was significantly associated with cancer-specific survival (CSS) (P = .05). CK5/6 expression strongly correlated with overall and disease-free survival, and CSS (P = .03, P = .04, and P = .03, respectively). Statistical significance was maintained for EGFR and CK5/6 after adjustment for covariates. CK14 was not associated with survival. All cell lines expressed similar levels of HER2. T and P alone inhibited proliferation of nonbasal cell lines; T + P had an additive cytotoxic effect. Basal cells were resistant to T, P inhibited proliferation, but T + P had no additive cytotoxic effect on cell growth in basal cells. Immunoblot analysis showed a significant decrease in phosphorylated Akt levels after treatment with T or T + P in nonbasal cells but not in basal cells. Akt blockade suppressed growth of basal and nonbasal HER2(+) cells. Furthermore, basal HER2 cell lines had increased mammosphere formation, which suggests increased stem cell properties compared with nonbasal HER2 cell lines.

CONCLUSION

CK5/6 and EGFR expression are predictive of worse prognosis in HER2(+) breast cancer patients treated with T. Basal HER2 breast cancer cell lines are resistant to trastuzamab, which is mediated through the Akt pathway; AKT inhibition abrogates this resistance. Basal HER2 cell lines also have increased stem cell properties, which might play a role in the resistance pathway.

Taxane-induced hedgehog signaling is linked to expansion of breast cancer stem-like populations after chemotherapy

Recurrence of breast cancer after chemotherapy is thought to arise from resistant breast cancer stem cells which are eventually able to repopulate the tumor. The Hedgehog (HH) signaling pathway has been shown to regulate the proliferation and survival of breast cancer stem cells, and has been shown to promote resistance to chemotherapy through the activation of multi-drug resistance and pro survival pathways. Here we report that exposure of heterogenous breast cancer cell lines to docetaxel (DOC) resulted in release of Sonic Hedgehog ligand (SHH) and activation of the HH pathway as evidenced by increased expression and nuclear translocation of the downstream effector Gli-1 at 4-24 h after DOC treatment. This activation had little effect on the bulk of the tumor cell population as inhibition of HH signaling failed to increase apoptosis in response to DOC. However, HH pathway activation was required for clonogenic growth of cell lines after DOC. Increases in stemness markers as well as mammosphere formation were observed after treatment with DOC suggesting an increase in the breast cancer stem cell populations. These increases were similar to that of cell lines cultured in the presence of recombinant SHH and could be eliminated by co-treatment with HH inhibitors. These results suggest that HH pathway activation induced by DOC treatment does not have a chemosensitizing effect on the heterogeneous tumor population, but may be required for survival and expansion of breast cancer stem cells after chemotherapy.