Resistance to Taxanes in Triple-Negative Breast Cancer Associates with the Dynamics of a CD49f+ Tumor-Initiating Population

The SRC-family serves as a therapeutic target in triple negative breast cancer with acquired resistance to chemotherapy

BACKGROUND

Resistance to chemotherapy, combined with heterogeneity among resistant tumors, represents a significant challenge in the clinical management of triple negative breast cancer (TNBC). By dissecting molecular pathways associated with treatment resistance, we sought to define patient sub-groups and actionable targets for next-line treatment.

METHODS

Bulk RNA sequencing and reverse phase protein array profiling were performed on isogenic patient-derived xenografts (PDX) representing paclitaxel-sensitive and -resistant tumors. Pathways identified as upregulated in the resistant model were further explored as targets in PDX explants. Their clinical relevance was assessed in two distinct patient cohorts (NeoAva and MET500).

RESULTS

Increased activity in signaling pathways involving SRC-family kinases (SFKs)- and MAPK/ERK was found in treatment resistant PDX, with targeted inhibitors being significantly more potent in resistant tumors. Up-regulation of SFKs- and MAPK/ERK-pathways was also detected in a sub-group of chemoresistant patients after neoadjuvant treatment. Furthermore, High SFK expression (of either SRC, FYN and/or YES1) was detected in metastatic lesions of TNBC patients with fast progressing disease (median disease-free interval 27 vs 105 months).

CONCLUSIONS

Upregulation of SFK-signaling is found in a subset of chemoresistant tumors and is persistent in metastatic lesions. Based on pre-clinical results, these patients may respond favorably to treatment targeting SFKs.

Exploiting Matrix Stiffness to Overcome Drug Resistance

Drug resistance is arguably one of the biggest challenges facing cancer research today. Understanding the underlying mechanisms of drug resistance in tumor progression and metastasis are essential in developing better treatment modalities. Given the matrix stiffness affecting the mechanotransduction capabilities of cancer cells, characterization of the related signal transduction pathways can provide a better understanding for developing novel therapeutic strategies. In this review, we aimed to summarize the recent advancements in tumor matrix biology in parallel to therapeutic approaches targeting matrix stiffness and its consequences in cellular processes in tumor progression and metastasis. The cellular processes governed by signal transduction pathways and their aberrant activation may result in activating the epithelial-to-mesenchymal transition, cancer stemness, and autophagy, which can be attributed to drug resistance. Developing therapeutic strategies to target these cellular processes in cancer biology will offer novel therapeutic approaches to tailor better personalized treatment modalities for clinical studies.

An Investigation into the In Vitro Targeted Killing of CD44-Expressing Triple-Negative Breast Cancer Cells Using Recombinant Photoimmunotherapeutics Compared to Auristatin-F-Based Antibody-Drug Conjugates

Triple-negative breast cancer (TNBC) is the deadliest form of breast cancer with limited treatment options. The persistence of highly tumorigenic CD44-expressing subpopulation referred to as cancer stem cells (CSCs), endowed with the self-renewal capacity, has been associated with therapeutic resistance, hence clinical relapses. To mitigate these undesired events, targeted immunotherapies using antibody-photoconjugate (APC) or antibody-drug conjugate (ADC), were developed to specifically release cytotoxic payloads within targeted cells overexpressing cognate antigen receptors. Therefore, an αCD44(scFv)-SNAP-tag antibody fusion protein was engineered through genetic fusion of a single-chain antibody fragment (scFv) to a SNAPf-tag fusion protein, capable of self-conjugating with benzylguanine-modified light-sensitive near-infrared (NIR) phthalocyanine dye IRDye700DX (BG-IR700) or the small molecule toxin auristatin-F (BG-AURIF). Binding of the αCD44(scFv)-SNAPf-IR700 photoimmunoconjugate to antigen-positive cells was demonstrated by confocal microscopy and flow cytometry. By switching to NIR irradiation, CD44-expressing TNBC was selectively killed through induced phototoxic activities. Likewise, the αCD44(scFv)-SNAPf-AURIF immunoconjugate was able to selectively accumulate within targeted cells and significantly reduced cell viability through antimitotic activities at nano- to micromolar drug concentrations. This study provides an in vitro proof-of-concept for a future strategy to selectively destroy light-accessible superficial CD44-expressing TNBC tumors and their metastatic lesions which are inaccessible to therapeutic light.

Impact of brain organoid-derived sEVs on metastatic adaptation and invasion of breast carcinoma cells through a microphysiological system

Brain metastases are common in triple-negative breast cancer (TNBC), suggesting a complex process of cancer spread. The mechanisms enabling TNBC cell adaptation and proliferation in the brain remain unclear. Small extracellular vesicles (sEVs) play a crucial role in communication between breast carcinoma cells and the brain. However, the lack of relevant models hinders understanding of sEV-mediated communication. The present study assesses the impact of brain organoid-derived sEVs (BO-sEVs) on various behaviours of the MDA-MB-231 cell line, chosen as a representative of TNBC in a 3D microfluidic model. Our results demonstrate that 150-200 nm sEVs expressing CD63, CD9, and CD81 from brain organoid media decrease MDA-MB-231 cell proliferation, enhance their wound-healing capacity, alter their morphology into more mesenchymal mode, and increase their stemness. BO-sEVs led to heightened PD-L1, CD49f, and vimentin levels of expression in MDA-MB-231 cells, suggesting an amplified immunosuppressive, stem-like, and mesenchymal phenotype. Furthermore, these sEVs also induced the expression of neural markers such as GFAP in carcinoma cells. The cytokine antibody profiling array also showed that BO-sEVs enhanced the secretion of MCP-1, IL-6, and IL-8 by MDA-MB-231 cells. Moreover, sEVs significantly enhance the migration and invasion of carcinoma cells toward brain organoids in a 3D organoid-on-a-chip system. Our findings emphasize the potential significance of metastatic site-derived sEVs as pivotal mediators in carcinoma progression and adaptation to the brain microenvironment, thereby unveiling novel therapeutic avenues.

Bcl-2 Up-Regulation Mediates Taxane Resistance Downstream of APC Loss

Triple-negative breast cancer (TNBC) patients are treated with traditional chemotherapy, such as the taxane class of drugs. One such drug, paclitaxel (PTX), can be effective in treating TNBC; however, many tumors will develop drug resistance, which can lead to recurrence. In order to improve patient outcomes and survival, there lies a critical need to understand the mechanism behind drug resistance. Our lab made the novel observation that decreased expression of the Adenomatous Polyposis Coli (APC) tumor suppressor using shRNA caused PTX resistance in the human TNBC cell line MDA-MB-157. In cells lacking APC, induction of apoptosis by PTX was decreased, which was measured through cleaved caspase 3 and annexin/PI staining. The current study demonstrates that CRISPR-mediated APC knockout in two other TNBC lines, MDA-MB-231 and SUM159, leads to PTX resistance. In addition, the cellular consequences and molecular mechanisms behind APC-mediated PTX response have been investigated through analysis of the BCL-2 family of proteins. We found a significant increase in the tumor-initiating cell population and increased expression of the pro-survival family member Bcl-2, which is widely known for its oncogenic behavior. ABT-199 (Venetoclax), is a BH3 mimetic that specifically targets Bcl-2. ABT-199 has been used as a single or combination therapy in multiple hematologic malignancies and has shown promise in multiple subtypes of breast cancer. To address the hypothesis that APC-induced Bcl-2 increase is responsible for PTX resistance, we combined treatment of PTX and ABT-199. This combination treatment of CRISPR-mediated APC knockout MDA-MB-231 cells resulted in alterations in apoptosis, suggesting that Bcl-2 inhibition restores PTX sensitivity in APC knockout breast cancer cells. Our studies are the first to show that Bcl-2 functional inhibition restores PTX sensitivity in APC mutant breast cancer cells. These studies are critical to advance better treatment regimens in patients with TNBC.

Efficacy and safety of veliparib combined with traditional chemotherapy for treating patients with lung cancer: a comprehensive review and meta-analysis

Objective

Lung cancer, originating from bronchial mucosa or lung glands, poses significant health risks due to its rising incidence and mortality. This study aimed to assess the efficacy and safety of Veliparib combined with chemotherapy versus pharmacotherapy alone for lung cancer treatment, guiding clinical approaches for this severe disease.

Methods

Comprehensive searches in PubMed, EMBASE, Cochrane, and Web of Science were conducted to identify randomized controlled trials (RCTs) comparing Veliparib combined with standard chemotherapy to chemotherapy alone in lung cancer treatment, up until December 28, 2022. Two reviewers meticulously selected literature based on inclusion and exclusion criteria. The Cochrane tool was used to assess the bias risk of the included studies, and meta-analysis was performed using Stata 15.0.

Results

Five RCTs (1,010 participants) were included. The analysis results showed that only Veliparib combinedwith chemotherapy prolonged the progression-free survival (PFS) in small cell lung cancer (SCLC) patients [HR = 0.72, 95% CI = (0.57, 0.90)]. No significant differences were observed in overall survival (OS) and objective response rate (ORR). Veliparib and combined chemotherapy caused some side effects in patients with lung cancer, including leukopenia [RR = 2.12, 95% CI = (1.27, 3.55)], neutropenia [RR = 1.51, 95% CI = (1.01, 2.26)], anemia [RR = 1.71, 95% CI = (1.07, 3.07)], and thrombocytopenia [RR = 3.33, 95% CI = (1.19, 9.30)]. For non-small cell lung cancer (NSCLC) patients, there were no statistically significant differences in PFS, OS, or ORR between the experimental and control groups [HR = 0.97, 95% CI = (0.75, 1.27)].

Conclusion

The strategy of combining Veliparib with chemotherapy may, to some extent, prolong the PFS in lung cancer patients. However, this benefit is not observed in OS or ORR. Additionally, there are evident adverse reactions. Due to a limited number of the included studies, additional extensive multicenter RCTs are required to validate these results. PROSPERO registration number: CRD42023411510.

RANK is a poor prognosis marker and a therapeutic target in ER-negative postmenopausal breast cancer

Despite strong preclinical data, the therapeutic benefit of the RANKL inhibitor, denosumab, in breast cancer patients, beyond the bone, is unclear. Aiming to select patients who may benefit from denosumab, we hereby analyzed RANK and RANKL protein expression in more than 2,000 breast tumors (777 estrogen receptor-negative, ER- ) from four independent cohorts. RANK protein expression was more frequent in ER- tumors, where it associated with poor outcome and poor response to chemotherapy. In ER- breast cancer patient-derived orthoxenografts (PDXs), RANKL inhibition reduced tumor cell proliferation and stemness, regulated tumor immunity and metabolism, and improved response to chemotherapy. Intriguingly, tumor RANK protein expression associated with poor prognosis in postmenopausal breast cancer patients, activation of NFKB signaling, and modulation of immune and metabolic pathways, suggesting that RANK signaling increases after menopause. Our results demonstrate that RANK protein expression is an independent biomarker of poor prognosis in postmenopausal and ER- breast cancer patients and support the therapeutic benefit of RANK pathway inhibitors, such as denosumab, in breast cancer patients with RANK+ ER- tumors after menopause.

Surface roughness modulates EGFR signaling and stemness of triple-negative breast cancer cells

Introduction: Cancer stem cells (CSC), a major culprit of drug-resistant phenotypes and tumor relapse, represent less than 2 % of the bulk of TNBC cells, making them difficult to isolate, study, and thus, limiting our understanding of the pathogenesis of the disease. Current methods for CSC enrichment, such as 3D spheroid culture, genetic modification, and stem cell conditioning, are time consuming, expensive, and unsuitable for high-throughput assays. One way to address these limitations is to use topographical stimuli to enhance CSC populations in planar culture. Physical cues in the breast tumor microenvironment can influence cell behavior through changes in the mechanical properties of the extracellular matrix (ECM). In this study, we used topographical cues on polystyrene films to investigate their effect on the proteome and stemness of standard TNBC cell lines. Methods: The topographical polystyrene-based array was generated using razor printing and polishing methods. Proteome data were analyzed and enriched bioprocesses were identified using R software. Stemness was assessed measuring CD44, CD24 and ALDH markers using flow cytometry, immunofluorescence, detection assays, and further validated with mammosphere assay. EGF/EGFR expression and activity was evaluated using enzyme-linked immunosorbent assay (ELISA), immunofluorescence and antibody membrane array. A dose-response assay was performed to further investigate the effect of surface topography on the sensitivity of cells to the EGFR inhibitor. Results: Surface roughness enriched the CSC population and modulated epidermal growth factor receptor (EGFR) signaling activity in TNBC cells. Enhanced proliferation of MDA-MB-468 cells in roughness correlated with upregulation of the epidermal growth factor (EGF) ligand, which in turn corresponded with a 3-fold increase in the expression of EGFR and a 42% increase in its phosphorylation compared to standard smooth culture surfaces. The results also demonstrated that phenotypic changes associated with topographical (roughness) stimuli significantly decreased the drug sensitivity to the EGFR inhibitor gefitinib. In addition, the proportion of CD44+/CD24-/ALDH+ was enhanced on surface roughness in both MDA-MB-231 and MDA-MB-468 cell lines. We also demonstrated that YAP/TAZ activation decreased in a roughness-dependent manner, confirming the mechanosensing effect of the topographies on the oncogenic activity of the cells. Discussion: Overall, this study demonstrates the potential of surface roughness as a culture strategy to influence oncogenic activity in TNBC cells and enrich CSC populations in planar cultures. Such a culture strategy may benefit high-throughput screening studies seeking to identify compounds with broader tumor efficacy.

The Role of Cancer Stem Cells and Their Extracellular Vesicles in the Modulation of the Antitumor Immunity

Cancer stem cells (CSCs) are a population of tumor cells that share similar properties to normal stem cells. CSCs are able to promote tumor progression and recurrence due to their resistance to chemotherapy and ability to stimulate angiogenesis and differentiate into non-CSCs. Cancer stem cells can also create a significant immunosuppressive environment around themselves by suppressing the activity of effector immune cells and recruiting cells that support tumor escape from immune response. The immunosuppressive effect of CSCs can be mediated by receptors located on their surface, as well as by secreted molecules, which transfer immunosuppressive signals to the cells of tumor microenvironment. In this article, the ability of CSCs to regulate the antitumor immune response and a contribution of CSC-derived EVs into the avoidance of the immune response are discussed.

Gypensapogenin I Suppresses Cell Proliferation in Triple-Negative Breast Cancer Via Triggering the Closure of AKT/GSK3β/β-Catenin and Notch-1 Signaling Pathways

Jiaogulan (Gynostemma pentaphyllum) tea is a functional food that is commercially available worldwide. Gypensapogenin I (Gyp I), which is a natural damarane-type saponin, was obtained from the hydrolysates of total gypenosides. The present research was performed to investigate the potential antiproliferation effect of Gyp I in MDA-MB-231 cells and the underlying mechanisms. Here, we found that Gyp I attenuated survival, inhibited proliferation, and induced apoptosis in MDA-MB-231 cells. Target prediction by binding molecule docking and western blot assays confirmed the mechanism by which Gyp I inhibited the proliferation of breast cancer cells via the AKT/GSK3β/β-catenin signaling pathway. We also showed that Gyp I exhibited superior in vivo efficacy that was dose dependent. Tumor tissue transcriptome analysis indicated that Gyp I could decrease the expression levels of NOTCH1 and HES1, which was in contrast to the effect on MAML and NUMBL, indicating that our compound hindered the activation of the Notch-1 signaling pathway. In summary, we report for the first time that Gyp I shows excellent anti-breast cancer activity in vivo and in vitro and that its pathway of action is related to the AKT/GSK3β/β-catenin and Notch-1 signaling pathways. Therefore, Jiaogulan tea can not only be used as a health food but also possesses the possibility to treat triple-negative breast cancer (TNBC).

Mechanisms of cancer stem cells drug resistance and the pivotal role of HMGA2

Nowadays, the focus of researchers is on perceiving the heterogeneity observed in a tumor. The researchers studied the role of a specific subset of cancer cells with high resistance to traditional treatments, recurrence, and unregulated metastasis. This small population of tumor cells that have stem-cell-like specifications was named Cancer Stem Cells (CSCs). The unique features that distinguish this type of cancer cell are self-renewing, generating clones of the tumor, plasticity, recurrence, and resistance to therapies. There are various mechanisms that contribute to the drug resistance of CSCs, such as CSCs markers, Epithelial mesenchymal transition, hypoxia, other cells, inflammation, and signaling pathways. Recent investigations have revealed the primary role of HMGA2 in the development and invasion of cancer cells. Importantly, HMGA2 also plays a key role in resistance to treatment through their function in the drug resistance mechanisms of CSCs and challenge it. Therefore, a deep understanding of this issue can provide a clearer perspective for researchers in the face of this problem.

miR-1205/DNAJB1 reverses docetaxel chemoresistance in human triple negative breast carcinoma cells via regulation of mutp53/TAp63 signaling

Chemoresistance is the major cause of therapeutic failure in human triple negative breast carcinoma (TNBC). Docetaxel (DOC), a first-line therapeutic drug in TNBC treatment, is limited for long-term use due to the development of chemoresistance. Thus, overcoming chemoresistance of DOC remains an important challenge to improve patient's outcome of TNBC. In this study, we aimed to investigate the molecular mechanism behind DOC chemoresistance and the possible therapeutic effects of miRNAs. Utilizing qRT-PCR analysis, we discovered that miR-1205 is gradually downregulated in human triple negative breast carcinoma MDA-MB-231 and docetaxel-resistant MDA-MB-231 (MDA-MB-231/DOC) cells compared with Hs 578Bst normal human breast fibroblasts. Cell viability, cell cycle and apoptosis assays in MDA-MB-231/DOC cells indicated that miR-1205 overexpression enhances docetaxel sensitivity by reducing cell viability as well as inducing G2/M cell cycle arrest and cell apoptosis. Western blot analysis, dual-luciferase reporter assay, co-immunoprecipitation assay and chromatin immunoprecipitation assay revealed that miR-1205 overexpression disrupts the stable complex formation of DNAJB1, mutp53 and TAp63 by directly reducing DNAJB1 expression, which abates the sequestrating effect of mutp53 on TAp63, thereby leading to the enhanced DOC sensitivity in MDA-MB-231/DOC cells. Our findings demonstrate the role of the miR-1205/DNAJB1 axis in the docetaxel resistance of TNBC, which may offer a promising therapeutic approach to resolve docetaxel resistance in TNBC.

AZD4547 targets the FGFR/Akt/SOX2 axis to overcome paclitaxel resistance in head and neck cancer

PURPOSE

Development of chemoresistance is one of the major obstacles to the treatment of head and neck squamous cell carcinoma (HNSCC). The PI3K/Akt pathway, involved in drug resistance, has been found to be overactivated in > 90% of HNSCCs. Aberrant activation of the FGF receptors (FGFRs) has been reported to cause overactivation of the PI3K/Akt pathway and to be associated with the maintenance of stem cell features, which is controlled via SOX2 expression. In this study, we aimed at investigating the potential of using AZD4547, an orally bioavailable FGFR inhibitor, to overcome taxol-resistance by targeting the FGFR/Akt/SOX2 axis in HNSCC.

METHODS

We initially evaluated FGFR2 and SOX2 expression using in silico tools. We analyzed the FGFR/Akt/SOX2 axis in normal/tumor tissue pairs and in recombinant FGF2 treated HNSCC cells. Next, we explored the effects of AZD4547 alone and in combination with taxol on the proliferation, migration and colony forming capacities of parental/taxol-resistant cells using in vitro models.

RESULTS

We found that the p-FGFR, p-AKT, p-GSK-3β and SOX2 expression levels were higher in tumor tissues than in its corresponding normal tissues, and that AZD4547 effectively suppressed the expression of FGFR and its downstream targets in recombinant FGF2 treated HNSCC cells. We also found that AZD4547 diminished the viability, migration and colony forming capacity of HNSCC cells, and that co-treatment with taxol potentiated the impact of taxol on these cells. Finally, we found that AZD4547 inhibited the overexpressed FGFR/Akt/SOX2 axis and profoundly suppressed cancer-related phenotypes in taxol-resistant HNSCC cells.

CONCLUSION

From our data we conclude that AZD4547 may increase the impact of taxol during HNSCC treatment. We suggest AZD4547 as a therapeutic agent to overcome taxol-resistance.

Chemoresistance in breast cancer: PI3K/Akt pathway inhibitors vs the current chemotherapy

Breast cancer is the most prevalent type of cancer among women. Several types of drugs, targeting the specific proteins expressed on the breast cancer cell surface (such as receptor tyrosine kinases and immune checkpoint regulators) and proteins involved in cell cycle and motility (including cyclin-dependent kinases, DNA stabilisers, and cytoskeleton modulators) are approved for different subtypes of breast cancer. However, breast cancer also has a poor response to conventional chemotherapy due to intrinsic and acquired resistance, and an Akt fingerprint is detectable in most drug-resistant cases. Overactivation of Akt and its upstream and downstream regulators in resistant breast cancer cells is considered a major potential target for novel anti-cancer therapies, suggesting that Akt signalling acts as a cellular mechanism against chemotherapy. The present review has shown that sustained activation of Akt results in resistance to different types of chemotherapy. Akt signalling plays a cellular defence role against chemotherapy and (1) enhances multi-drug resistance, (2) increases reactive oxygen species at breast tumor microenvironment, (3) enhances anaerobic metabolism, (4) inhibits the tricarboxylic cycle, (5) promotes PD-L1 upregulation, (6) inhibits apoptosis, (7) increases glucose uptake, and more importantly (8) recruits and interconnects the plasma membrane, nucleus, endoplasmic reticulum, and mitochondria to hijack breast cancer cells and rescue these cells from chemotherapy. Therefore, Akt signalling is considered a cellular defence mechanism employed against chemotherapeutic effects. In addition, interfering roles of PI3K/Akt signalling on the current cytotoxic and molecularly targeted therapy as well as immunotherapy of breast cancer are discussed with a clinical approach. Although, alpelisib, a PIK3CA inhibitor, is the only PI3K/Akt pathway inhibitor approved for breast cancer, we also highlight well-evaluated inhibitors of PI3K/Akt signalling based on different subtypes of breast cancer, which are under clinical trials whether as monotherapy or in combination with other types of chemotherapy.

BMP4 enhances anoikis resistance and chemoresistance of breast cancer cells through canonical BMP signaling

Bone morphogenetic proteins (BMPs) regulate cell fate during development and mediate cancer progression. In this study, we investigated the role of BMP4 in proliferation, anoikis resistance, metastatic migration, and drug resistance of breast cancer cells. We utilized breast cancer cell lines and clinical samples representing different subtypes to understand the functional effect of BMP4 on breast cancer. The BMP pathway was inhibited with the small molecule inhibitor LDN193189 hydrochloride (LDN). BMP4 signaling enhanced the expression of stem cell genes CD44, ALDH1A3, anti-apoptotic gene BCL2 and promoted anoikis resistance in MDA-MB-231 breast cancer cells. BMP4 enhanced self-renewal and chemoresistance in MDA-MB-231 by upregulating Notch signaling while LDN treatment abrogated anoikis resistance and proliferation of anoikis resistant breast cancer cells in the osteogenic microenvironment. Conversely, BMP4 downregulated proliferation, colony-forming ability, and suppressed anoikis resistance in MCF7 and SkBR3 cells, while LDN treatment promoted tumor spheroid formation and growth. These findings indicate that BMP4 has a context-dependent role in breast cancer. Further, our data with MDA-MB-231 cells representing triple-negative breast cancer suggest that BMP inhibition might impair its metastatic spread and colonization.

Molecular mechanisms of chemo- and radiotherapy resistance and the potential implications for cancer treatment

Cancer is a leading cause of death worldwide. Surgery is the primary treatment approach for cancer, but the survival rate is very low due to the rapid progression of the disease and presence of local and distant metastasis at diagnosis. Adjuvant chemotherapy and radiotherapy are important components of the multidisciplinary approaches for cancer treatment. However, resistance to radiotherapy and chemotherapy may result in treatment failure or even cancer recurrence. Radioresistance in cancer is often caused by the repair response to radiation-induced DNA damage, cell cycle dysregulation, cancer stem cells (CSCs) resilience, and epithelial-mesenchymal transition (EMT). Understanding the molecular alterations that lead to radioresistance may provide new diagnostic markers and therapeutic targets to improve radiotherapy efficacy. Patients who develop resistance to chemotherapy drugs cannot benefit from the cytotoxicity induced by the prescribed drug and will likely have a poor outcome with these treatments. Chemotherapy often shows a low response rate due to various drug resistance mechanisms. This review focuses on the molecular mechanisms of radioresistance and chemoresistance in cancer and discusses recent developments in therapeutic strategies targeting chemoradiotherapy resistance to improve treatment outcomes.

Vimentin Promotes the Aggressiveness of Triple Negative Breast Cancer Cells Surviving Chemotherapeutic Treatment

Tremendous data have been accumulated in the effort to understand chemoresistance of triple negative breast cancer (TNBC). However, modifications in cancer cells surviving combined and sequential treatment still remain poorly described. In order to mimic clinical neoadjuvant treatment, we first treated MDA-MB-231 and SUM159-PT TNBC cell lines with epirubicin and cyclophosphamide for 2 days, and then with paclitaxel for another 2 days. After 4 days of recovery, persistent cells surviving the treatment were characterized at both cellular and molecular level. Persistent cells exhibited increased growth and were more invasive in vitro and in zebrafish model. Persistent cells were enriched for vimentin^high sub-population, vimentin knockdown using siRNA approach decreased the invasive and sphere forming capacities as well as Akt phosphorylation in persistent cells, indicating that vimentin is involved in chemotherapeutic treatment-induced enhancement of TNBC aggressiveness. Interestingly, ectopic vimentin overexpression in native cells increased cell invasion and sphere formation as well as Akt phosphorylation. Furthermore, vimentin overexpression alone rendered the native cells resistant to the drugs, while vimentin knockdown rendered them more sensitive to the drugs. Together, our data suggest that vimentin could be considered as a new targetable player in the ever-elusive status of drug resistance and recurrence of TNBC.

Epigenetic Awakening of Viral Mimicry in Cancer

In this issue, Deblois and colleagues show how taxane-resistant triple-negative breast cancer cells evade viral mimicry response as a result of metabolic alteration, DNA hypomethylation, and relocation of histone H3K27 trimethylation (H3K27me3). This adaptation confers a therapeutic vulnerability to the inhibition of the H3K27me3 methyltransferase EZH2 in resistant cells, leading to tumor growth inhibition by viral mimicry reactivation.See related article by Deblois et al., p. 1312.

A Novel Thienopyrimidine Analog, TPH104, Mediates Immunogenic Cell Death in Triple-Negative Breast Cancer Cells

Simple Summary

Triple-negative breast cancer (TNBC) is the most lethal and aggressive subtype of breast cancer that lacks an estrogen receptor, the progesterone receptor and the human epidermal growth factor receptor 2 (HER2), making it unsuitable for hormonal- or HER2-based therapy. TNBC is known for its higher relapse rate, poorer prognosis and higher rate of metastasis compared to non-TNBC because although patients initially respond to chemotherapy that kills cancer cells through a form of programmed cell death called apoptosis, they later develop chemoresistance and stop responding to the treatment, accounting for one fourth of all breast cancer deaths. In this study, we report a novel compound, TPH104, that elicits a unique, non-apoptotic cell death in TNBC cells. Upon treatment with TPH104, TNBC cells swell and burst, releasing immunogenic markers that alert and activate the immune system to further recognize and attack the neighboring breast cancer cells.

Abstract

Enhancing the tumor immunogenic microenvironment has been suggested to circumvent triple-negative breast cancer (TNBC) resistance and increase the efficacy of conventional chemotherapy. Here, we report a novel chemotherapeutic compound, TPH104, which induces immunogenic cell death in the TNBC cell line MDA-MB-231, by increasing the stimulatory capacity of dendritic cells (DCs), with an IC₅₀ value of 140 nM. TPH104 (5 µM) significantly increased ATP levels in the supernatant and mobilized intracellular calreticulin to the plasma membrane in MDA-MB-231 cells, compared to cells incubated with the vehicle. Incubating MDA-MB-231 cells for 12 h with TPH104 (1–5 µM) significantly increased TNF-α mRNA levels. The supernatants of dying MDAMB-231 cells incubated with TPH104 increased mouse bone marrow-derived DC maturation, the expression of MHC-II and CD86 and the mRNA expression of TNF-α, IL-6 and IL-12. Overall, these results indicate that TPH104 induces immunogenic cell death in TNBC cells, in part, by activating DCs.

Antitumor Activity of Pulvomycin via Targeting Activated-STAT3 Signaling in Docetaxel-Resistant Triple-Negative Breast Cancer Cells

Although docetaxel-based regimens are common and effective for early-stage triple-negative breast cancer (TNBC) treatment, acquired drug resistance frequently occurs. Therefore, a novel therapeutic strategy for docetaxel-resistant TNBC is urgently required. Signal transducer and activator of transcription 3 (STAT3) plays a pivotal role in the tumorigenesis and metastasis of numerous cancers, and STAT3 signaling is aberrantly activated in TNBC cells. In this study, a docetaxel-resistant TNBC cell line (MDA-MB-231-DTR) was established, and mechanisms for the antitumor activity of pulvomycin, a novel STAT3 inhibitor isolated from marine-derived actinomycete, were investigated. Levels of activated STAT3 (p-STAT3 (Y705)) increased in docetaxel-resistant cells, and knockdown of STAT3 recovered the sensitivity to docetaxel in MDA-MB-231-DTR cells. Pulvomycin effectively inhibited the proliferation of both cell lines. In addition, pulvomycin suppressed the activation of STAT3 and subsequently induced G0/G1 cell cycle arrest and apoptosis. Pulvomycin also significantly inhibited the invasion and migration of MDA-MB-231-DTR cells through the modulation of epithelial-mesenchymal transition markers. In an MDA-MB-231-DTR-bearing xenograft mouse model, the combination of pulvomycin and docetaxel effectively inhibited tumor growth through STAT3 regulation. Thus, our findings demonstrate that the combination of docetaxel and STAT3 inhibitors is an effective strategy for overcoming docetaxel resistance in TNBC.

Laboratory Models for Investigating Breast Cancer Therapy Resistance and Metastasis

While numerous therapies are highly efficacious in early-stage breast cancers and in particular subsets of breast cancers, therapeutic resistance and metastasis unfortunately arise in many patients. In many cases, tumors that are resistant to standard of care therapies, as well as tumors that have metastasized, are treatable but incurable with existing clinical strategies. Both therapy resistance and metastasis are multi-step processes during which tumor cells must overcome diverse environmental and selective hurdles. Mechanisms by which tumor cells achieve this are numerous and include acquisition of invasive and migratory capabilities, cell-intrinsic genetic and/or epigenetic adaptations, clonal selection, immune evasion, interactions with stromal cells, entering a state of dormancy or senescence, and maintaining self-renewal capacity. To overcome therapy resistance and metastasis in breast cancer, the ability to effectively model each of these mechanisms in the laboratory is essential. Herein we review historic and the current state-of-the-art laboratory model systems and experimental approaches used to investigate breast cancer metastasis and resistance to standard of care therapeutics. While each model system has inherent limitations, they have provided invaluable insights, many of which have translated into regimens undergoing clinical evaluation. We will discuss the limitations and advantages of a variety of model systems that have been used to investigate breast cancer metastasis and therapy resistance and outline potential strategies to improve experimental modeling to further our knowledge of these processes, which will be crucial for the continued development of effective breast cancer treatments.

Drug resistance and Cancer stem cells

Therapy resistance is a major problem when treating cancer patients as cancer cells develop mechanisms that counteract the effect of therapeutic compounds, leading to fit and more aggressive clones that contribute to poor prognosis. Therapy resistance can be both intrinsic and/or acquired. These are multifactorial events, and some are related to factors including adaptations in cancer stem cells (CSCs), epithelial-mesenchymal transition (EMT), deregulation of key signaling pathways, drug efflux through ABC transporters, acquired mutations, evading apoptosis, and activation of DNA damage response among others. Among these factors, CSCs represent the major source of therapy resistance. CSCs are a subset of tumor cells that are capable of self-renewal and multilineage progenitor expansion that are known to be intrinsically resistant to anticancer treatments. Multiple clones of CSCs pre-exist, and some can adopt and expand easily to changes in the tumor microenvironment (TME) and/or in response to radio- and chemotherapy. A combination of both intrinsic and extrinsic factors contributes to CSC-mediated therapy resistance. In this review, we will focus on CSCs and therapy resistance as well as suggest strategies to eliminate CSCs and, therefore, overcome resistance. Video abstract.

LDH-doped electrospun short fibers enable dual drug loading and multistage release for chemotherapy of drug-resistant cancer cells

LDH-incorporated PLGA short nanofibers can be loaded with dual drugs for multistage release and chemotherapy of drug-resistant cancer cells.

Evaluation of chemotherapy and P2Et extract combination in ex-vivo derived tumor mammospheres from breast cancer patients

The main cause of death by cancer is metastasis rather than local complications of primary tumors. Recent studies suggest that breast cancer stem cells (BCSCs), retains the ability to self-renew and differentiate to repopulate the entire tumor, also, they have been associated with resistance to chemotherapy and tumor recurrence, even after tumor resection. Chemotherapy has been implicated in the induction of resistant phenotypes with highly metastatic potential. Naturally occurring compounds, especially phytochemicals such as P2Et, can target different populations of cancer cells as well as BCSC, favoring the activation of immune response via immunogenic tumor death. Here, we evaluated the presence of BCSC as well as markers related to drug resistance in tumors obtained from 78 patients who had received (or not) chemotherapy before surgery. We evaluated the ex vivo response of patient tumor-derived organoids (or mammospheres) to chemotherapy alone or in combination with P2Et. A xenotransplant model engrafted with MDA-MB-468 was used to evaluate in vivo the activity of P2Et, in this model P2Et delay tumor growth. We show that patients with luminal and TNBC, and those who received neoadjuvant therapy before surgery have a higher frequency of BCSC. Further, the treatment with P2Et in mammospheres and human breast cancer cell lines improve the in vitro tumor death and decrease its viability and proliferation together with the release of immunogenic signals. P2Et could be a good co-adjuvant in antitumor therapy in patients, retarding the tumor growth by enabling the activation of the immune response.

Mechanisms of Taxane Resistance

The taxane family of chemotherapy drugs has been used to treat a variety of mostly epithelial-derived tumors and remain the first-line treatment for some cancers. Despite the improved survival time and reduction of tumor size observed in some patients, many have no response to the drugs or develop resistance over time. Taxane resistance is multi-faceted and involves multiple pathways in proliferation, apoptosis, metabolism, and the transport of foreign substances. In this review, we dive deeper into hypothesized resistance mechanisms from research during the last decade, with a focus on the cancer types that use taxanes as first-line treatment but frequently develop resistance to them. Furthermore, we will discuss current clinical inhibitors and those yet to be approved that target key pathways or proteins and aim to reverse resistance in combination with taxanes or individually. Lastly, we will highlight taxane response biomarkers, specific genes with monitored expression and correlated with response to taxanes, mentioning those currently being used and those that should be adopted. The future directions of taxanes involve more personalized approaches to treatment by tailoring drug-inhibitor combinations or alternatives depending on levels of resistance biomarkers. We hope that this review will identify gaps in knowledge surrounding taxane resistance that future research or clinical trials can overcome.

High accuracy gene expression profiling of sorted cell subpopulations from breast cancer PDX model tissue

Intratumor Heterogeneity (ITH) is a functionally important property of tumor tissue and may be involved in drug resistance mechanisms. Although descriptions of ITH can be traced back to very early reports about cancer tissue, mechanistic investigations are still limited by the precision of analysis methods and access to relevant tissue sources. PDX models have provided a reproducible source of tissue with at least a partial representation of naturally occurring ITH. We investigated the properties of phenotypically distinct cell populations by Fluorescence activated cell sorting (FACS) tissue derived cells from multiple tumors from a triple negative breast cancer patient derived xenograft (PDX) model. We subsequently subjected each population to in depth gene expression analysis. Our findings suggest that process related gene expression changes (caused by tissue dissociation and FACS sorting) are restricted to Immediate Early Genes (IEGs). This allowed us to discover highly reproducible gene expression profiles of distinct cellular compartments identifiable by cell surface markers in this particular tumor model. Within the context of data from a previously published model our work suggests that gene expression profiles associated with hypoxia, stemness and drug resistance may reside in tumor subpopulations predictably growing in PDX models. This approach provides a novel opportunity for prospective mechanistic studies of ITH.

Cancer Stem Cells-Origins and Biomarkers: Perspectives for Targeted Personalized Therapies

The use of biomarkers in diagnosis, therapy and prognosis has gained increasing interest over the last decades. In particular, the analysis of biomarkers in cancer patients within the pre- and post-therapeutic period is required to identify several types of cells, which carry a risk for a disease progression and subsequent post-therapeutic relapse. Cancer stem cells (CSCs) are a subpopulation of tumor cells that can drive tumor initiation and can cause relapses. At the time point of tumor initiation, CSCs originate from either differentiated cells or adult tissue resident stem cells. Due to their importance, several biomarkers that characterize CSCs have been identified and correlated to diagnosis, therapy and prognosis. However, CSCs have been shown to display a high plasticity, which changes their phenotypic and functional appearance. Such changes are induced by chemo- and radiotherapeutics as well as senescent tumor cells, which cause alterations in the tumor microenvironment. Induction of senescence causes tumor shrinkage by modulating an anti-tumorigenic environment in which tumor cells undergo growth arrest and immune cells are attracted. Besides these positive effects after therapy, senescence can also have negative effects displayed post-therapeutically. These unfavorable effects can directly promote cancer stemness by increasing CSC plasticity phenotypes, by activating stemness pathways in non-CSCs, as well as by promoting senescence escape and subsequent activation of stemness pathways. At the end, all these effects can lead to tumor relapse and metastasis. This review provides an overview of the most frequently used CSC markers and their implementation as biomarkers by focussing on deadliest solid (lung, stomach, liver, breast and colorectal cancers) and hematological (acute myeloid leukemia, chronic myeloid leukemia) cancers. Furthermore, it gives examples on how the CSC markers might be influenced by therapeutics, such as chemo- and radiotherapy, and the tumor microenvironment. It points out, that it is crucial to identify and monitor residual CSCs, senescent tumor cells, and the pro-tumorigenic senescence-associated secretory phenotype in a therapy follow-up using specific biomarkers. As a future perspective, a targeted immune-mediated strategy using chimeric antigen receptor based approaches for the removal of remaining chemotherapy-resistant cells as well as CSCs in a personalized therapeutic approach are discussed.

Mechanistic Involvement of Long Non-Coding RNAs in Oncotherapeutics Resistance in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is one of the most lethal forms of breast cancer (BC), with a significant disease burden worldwide. Chemoresistance and lack of targeted therapeutics are major hindrances to effective treatments in the clinic and are crucial causes of a worse prognosis and high rate of relapse/recurrence in patients diagnosed with TNBC. In the last decade, long non-coding RNAs (lncRNAs) have been found to perform a pivotal role in most cellular functions. The aberrant functional expression of lncRNAs plays an ever-increasing role in the progression of diverse malignancies, including TNBC. Therefore, lncRNAs have been recently studied as predictors and modifiers of chemoresistance. Our review discusses the potential involvement of lncRNAs in drug-resistant mechanisms commonly found in TNBC and highlights various therapeutic strategies to target lncRNAs in this malignancy.

Sorafenib Inhibits Proliferation, Migration and Invasion of Breast Cancer Cells

INTRODUCTION

Metastatic breast cancer has poor prognosis due to limited therapeutic options. Protein kinase dysregulations have a major role in breast cancer progression and metastasis. In this study, we investigated the anti-cancer activity of sorafenib, a multikinase inhibitor, which targets receptor tyrosine kinases in breast cancer. Although treatment with sorafenib has increased the patient survival and inhibited metastatic migration in hepatocellular carcinoma, its role in breast cancer migration, metastasis, and intracellular signaling modulation is unknown.

METHODS

Breast cancer cell lines MCF7 and MDA-MB-231 were treated with sorafenib and its effect on proliferation, migration, invasion and gene expression was analyzed.

RESULTS

We found that sorafenib has an anti-proliferative and cytotoxic effect on breast cancer cells. Importantly, sorafenib inhibited the migration and invasion of breast cancer cells in vitro. Mechanistically, sorafenib increased mitochondrial superoxide production, suppressed breast cancer stem cell self-renewal, inhibited epithelial mesenchymal transition and ERK signaling.

CONCLUSION

Thus, sorafenib has anti-cancer activity against breast cancer cells and could improve the survival of breast cancer patients by inhibiting their invasive and metastatic properties.

The Missing Lnc: The Potential of Targeting Triple-Negative Breast Cancer and Cancer Stem Cells by Inhibiting Long Non-Coding RNAs

Treatment decisions for breast cancer are based on staging and hormone receptor expression and include chemotherapies and endocrine therapy. While effective in many cases, some breast cancers are resistant to therapy, metastasize and recur, leading to eventual death. Higher percentages of tumor-initiating cancer stem cells (CSCs) may contribute to the increased aggressiveness, chemoresistance, and worse outcomes among breast cancer. This may be particularly true in triple-negative breast cancers (TNBCs) which have higher percentages of CSCs and are associated with worse outcomes. In recent years, increasing numbers of long non-coding RNAs (lncRNAs) have been identified as playing an important role in breast cancer progression and some of these have been specifically associated within the CSC populations of breast cancers. LncRNAs are non-protein-coding transcripts greater than 200 nucleotides which can have critical functions in gene expression regulation. The preclinical evidence regarding lncRNA antagonists for the treatment of cancer is promising and therefore, presents a potential novel approach for treating breast cancer and targeting therapy-resistant CSCs within these tumors. Herein, we summarize the lncRNAs that have been identified as functionally relevant in breast CSCs. Furthermore, our review of the literature and analysis of patient datasets has revealed that many of these breast CSC-associated lncRNAs are also enriched in TNBC. Together, this suggests that these lncRNAs may be playing a particularly important role in TNBC. Thus, certain breast cancer-promoting/CSC-associated lncRNAs could be targeted in the treatment of TNBCs and the CSCs within these tumors should be susceptible to anti-lncRNA therapy.

Clinical Evolution of Epithelial-Mesenchymal Transition in Human Carcinomas

The significance of the phenotypic plasticity afforded by epithelial-mesenchymal transition (EMT) for cancer progression and drug resistance remains to be fully elucidated in the clinic. We evaluated epithelial-mesenchymal phenotypic characteristics across a range of tumor histologies using a validated, high-resolution digital microscopic immunofluorescence assay (IFA) that incorporates β-catenin detection and cellular morphology to delineate carcinoma cells from stromal fibroblasts and that quantitates the individual and colocalized expression of the epithelial marker E-cadherin (E) and the mesenchymal marker vimentin (V) at subcellular resolution ("EMT-IFA"). We report the discovery of β-catenin+ cancer cells that coexpress E-cadherin and vimentin in core-needle biopsies from patients with various advanced metastatic carcinomas, wherein these cells are transitioning between strongly epithelial and strongly mesenchymal-like phenotypes. Treatment of carcinoma models with anticancer drugs that differ in their mechanism of action (the tyrosine kinase inhibitor pazopanib in MKN45 gastric carcinoma xenografts and the combination of tubulin-targeting agent paclitaxel with the BCR-ABL inhibitor nilotinib in MDA-MB-468 breast cancer xenografts) caused changes in the tumor epithelial-mesenchymal character. Moreover, the appearance of partial EMT or mesenchymal-like carcinoma cells in MDA-MB-468 tumors treated with the paclitaxel-nilotinib combination resulted in upregulation of cancer stem cell (CSC) markers and susceptibility to FAK inhibitor. A metastatic prostate cancer patient treated with the PARP inhibitor talazoparib exhibited similar CSC marker upregulation. Therefore, the phenotypic plasticity conferred on carcinoma cells by EMT allows for rapid adaptation to cytotoxic or molecularly targeted therapy and could create a form of acquired drug resistance that is transient in nature. SIGNIFICANCE: Despite the role of EMT in metastasis and drug resistance, no standardized assessment of EMT phenotypic heterogeneity in human carcinomas exists; the EMT-IFA allows for clinical monitoring of tumor adaptation to therapy.

B7-H3-targeted Radioimmunotherapy of Human Cancer

BACKGROUND

Targeted Radioimmunotherapy (RIT) is an attractive approach to selectively localize therapeutic radionuclides to malignant cells within primary and metastatic tumors while sparing normal tissues from the effects of radiation. Many human malignancies express B7-H3 on the tumor cell surface, while expression on the majority of normal tissues is limited, presenting B7-H3 as a candidate target for RIT. This review provides an overview of the general principles of targeted RIT and discusses publications that have used radiolabeled B7-H3-targeted antibodies for RIT of cancer in preclinical or clinical studies.

METHODS

Databases including PubMed, Scopus, and Google Scholar were searched for publications through June 2018 using a combination of terms including "B7-H3", "radioimmunotherapy", "targeted", "radiotherapy", and "cancer". After screening search results for relevancy, ten publications were included for discussion.

RESULTS

B7-H3-targeted RIT studies to date range from antibody development and assessment of novel Radioimmunoconjugates (RICs) in animal models of human cancer to phase II/III trials in humans. The majority of clinical studies have used B7-H3-targeted RICs for intra- compartment RIT of central nervous system malignancies. The results of these studies have indicated high tolerability and favorable efficacy outcomes, supporting further assessment of B7-H3-targeted RIT in larger trials. Preclinical B7-H3-targeted RIT studies have also shown encouraging therapeutic outcomes in a variety of solid malignancies.

CONCLUSION

B7-H3-targeted RIT studies over the last 15 years have demonstrated feasibility for clinical development and support future assessment in a broader array of human malignancies. Future directions worthy of exploration include strategies that combine B7-H3- targeted RIT with chemotherapy or immunotherapy.

Schlafen12 Reduces the Aggressiveness of Triple Negative Breast Cancer through Post-Transcriptional Regulation of ZEB1 That Drives Stem Cell Differentiation

BACKGROUND/AIMS

Schlafen12 (SLFN12) promotes human intestinal and prostatic epithelial differentiation. We sought to determine whether SLFN12 reduces triple-negative breast cancer (TNBC) aggressiveness.

METHODS

We validated bioinformatics analyses of publicly available databases by staining human TNBC. After virally overexpressing or siRNA-reducing SLFN12 in TNBC cell lines, we measured proliferation by CCK-8 assay, invasion into basement-membrane-coated pores, mRNA by q-RT-PCR and protein by Western blotting. Flow cytometry assessed proliferation and stem cell marker expression, and sorted CD44+/CD24- cells. Stemness was also assessed by mammosphere formation, and translation by click-it-AHA chemistry.

RESULTS

SLFN12 expression was lower in TNBC tumors and correlated with survival. SLFN12 overexpression reduced TNBC MDA-MB-231, BT549, and Hs578T proliferation. In MDA-MB-231 cells, AdSLFN12 reduced invasion, promoted cell cycle arrest, increased E-cadherin promoter activity, mRNA, and protein, and reduced vimentin expression and protein. SLFN12 knockdown increased vimentin. AdSLFN12 reduced the proportion of MDA-MB-231 CD44⁺CD24^- cells, with parallel differentiation changes. SLFN12 overexpression reduced MDA-MB-231 mammosphere formation. SLFN12 overexpression decreased ZEB1 and Slug protein despite increased ZEB1 and Slug mRNA in all three lines. SLFN12 overexpression accelerated MDA-MB-231 ZEB1 proteasomal degradation and slowed ZEB1 translation. SLFN12 knockdown increased ZEB1 protein. Coexpressing ZEB1 attenuated the SLFN12 effect on E-cadherin mRNA and proliferation in all three lines.

CONCLUSION

SLFN12 may reduce TNBC aggressiveness and improve survival in part by a post-transcriptional decrease in ZEB1 that promotes TNBC cancer stem cell differentiation.

Targeting Breast Cancer Stem Cells: A Methodological Perspective

Cancer Stem Cells (CSCs) constitute a subpopulation at the top of the tumor cell hierarchy that contributes to tumor heterogeneity and is uniquely capable of seeding new tumors. Because of their biological properties, CSCs have been pointed out as therapeutic targets for the development of new therapies against breast cancer. The identification of drugs that selectively target breast CSCs requires a clear understanding of their biological functions and the experimental methods to evaluate such hallmarks. Herein, we review the methods to study breast CSCs properties and discuss their value in the preclinical evaluation of CSC-targeting drugs.

The GEF-H1/PKD3 signaling pathway promotes the maintenance of triple-negative breast cancer stem cells

Protein kinase D3 (PKD3) is upregulated in triple-negative breast cancer (TNBC) and associated with cell proliferation and metastasis development but its precise pro-oncogenic function is unknown. Here we show that PKD3 is required for the maintenance of the TNBC stem cell population. The depletion of PKD3 in MDA-MB-231 cells reduced the cancer stem cell frequency in vitro and tumor initiation potential in vivo. We further provide evidence that the RhoGEF GEF-H1 is upstream of PKD3 activation in TNBC stem cells. Most importantly, pharmacological PKD inhibition in combination with paclitaxel synergistically decreased oncosphere and colony formation efficiency in vitro and tumor recurrence in vivo. Based on our results we propose that targeting the GEF-H1/PKD3 signaling pathway in combination with chemotherapy might provide an effective therapeutic option for TNBC.

Identification of FOXE3 transcription factor as a potent oncogenic factor in triple-negative breast cancer

Triple-negative breast cancer (TNBC) represents a unique subgroup of breast cancers (BCa) with potential to be highly proliferative and invasive. Patient with TNBC are prone to developing resistance to chemotherapy. Therefore, TNBC usually has a poor clinical outcome. The key factors driving these malignant features remain poorly understood. In this study, we report for the first time that expression levels of FOXE3, a recently identified lens-specific transcription factor, were preferentially upregulated in TNBC tissues compared to non-TNBC tissues, and this upregulation correlated well to a poor overall/recurrence-free survival in patients. Depletion of FOXE3 in TNBC cell lines promoted cell death, cell cycle arrest, and potentiated sensitivity to docetaxel (DTX), a first-line chemotherapeutic drug for TNBC treatment. These alterations in cell growth/survival properties were accompanied by induction of CDKN1B, a gene encoding the tumor suppressor p27. We further provided the molecular evidence that FOXE3 could directly bind to the CDKN1B promoter and negatively regulate its transcription in TNBC cells. Importantly, knockdown of combined p27 and FOXE3 reversed the DTX-induced cell growth inhibition observed upon FOXE3 knockdown, indicating that the FOXE3's effects on TNBC progression were mediated mainly through transcriptional regulation of the p27 signaling. Together, our findings suggest that FOXE3 may function as a potent oncogene during the progression of TNBC, likely affecting cell proliferation, invasion and chemosensitivity, and functioning at least in part through transcriptional repression of p27 signaling.

Novel and Alternative Targets Against Breast Cancer Stemness to Combat Chemoresistance

Breast cancer stem cells (BCSCs) play a vital role in tumor progression and metastasis. They are heterogeneous and inherently radio- and chemoresistant. They have the ability to self-renew and differentiate into non-BCSCs. These determinants of BCSCs including the plasticity between the mesenchymal and epithelial phenotypes often leads to minimal residual disease (MRD), tumor relapse, and therapy failure. By studying the resistance mechanisms in BCSCs, a combinatorial therapy can be formulated to co-target BCSCs and bulk tumor cells. This review addresses breast cancer stemness and molecular underpinnings of how the cancer stemness can lead to pharmacological resistance. This might occur through rewiring of signaling pathways and modulated expression of various targets that support survival and self-renewal, clonogenicity, and multi-lineage differentiation into heterogeneous bulk tumor cells following chemotherapy. We explore emerging novel and alternative molecular targets against BC stemness and chemoresistance involving survival, drug efflux, metabolism, proliferation, cell migration, invasion, and metastasis. Strategic targeting of such vulnerabilities in BCSCs may overcome the chemoresistance and increase the longevity of the metastatic breast cancer patients.

Chromosome 12p Amplification in Triple-Negative/BRCA1-Mutated Breast Cancer Associates with Emergence of Docetaxel Resistance and Carboplatin Sensitivity

Taxanes are the mainstay of treatment in triple-negative breast cancer (TNBC), with de novo and acquired resistance limiting patient's survival. To investigate the genetic basis of docetaxel resistance in TNBC, exome sequencing was performed on matched TNBC patient-derived xenografts (PDX) sensitive to docetaxel and their counterparts that developed resistance in vivo upon continuous drug exposure. Most mutations, small insertions/deletions, and copy number alterations detected in the initial TNBC human metastatic samples were maintained after serial passages in mice and emergence of resistance. We identified a chromosomal amplification of chr12p in a human BRCA1-mutated metastatic sample and the derived chemoresistant PDX, but not in the matched docetaxel-sensitive PDX tumor. Chr12p amplification was validated in a second pair of docetaxel-sensitive/resistant BRCA1-mutated PDXs and after short-term docetaxel treatment in several TNBC/BRCA1-mutated PDXs and cell lines, as well as during metastatic recurrence in a patient with BRCA1-mutated breast cancer who had progressed on docetaxel treatment. Analysis of clinical data indicates an association between chr12p amplification and patients with TNBC/basal-like breast cancer, a BRCA1 mutational signature, and poor survival after chemotherapy. Detection of chr12p amplification in a cohort of TNBC PDX models was associated with an improved response to carboplatin. Our findings reveal tumor clonal dynamics during chemotherapy treatments and suggest that a preexisting population harboring chr12p amplification is associated with the emergence of docetaxel resistance and carboplatin responsiveness in TNBC/BRCA1-mutated tumors. SIGNIFICANCE: Chr12p copy number gains indicate rapid emergence of resistance to docetaxel and increased sensitivity to carboplatin, therefore sequential docetaxel/carboplatin treatment could improve survival in TNBC/BRCA1 patients. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/79/16/4258/F1.large.jpg.

The Altered Transcriptome and DNA Methylation Profiles of Docetaxel Resistance in Breast Cancer PDX Models

Taxanes are standard therapy in clinical practice for metastatic breast cancer; however, primary or acquired chemoresistance are a common cause of mortality. Breast cancer patient-derived xenografts (PDX) are powerful tools for the study of cancer biology and drug treatment response. Specific DNA methylation patterns have been associated to different breast cancer subtypes but its association with chemoresistance remains unstudied. Aiming to elucidate docetaxel resistance mechanisms, we performed genome-wide DNA methylation in breast cancer PDX models, including luminal and triple-negative breast cancer (TNBC) models sensitive to docetaxel, their matched models after emergence of chemoresistance and residual disease after short-term docetaxel treatment. We found that DNA methylation profiles from breast cancer PDX models maintain the subtype-specific methylation patterns of clinical samples. Two main DNA methylation clusters were found in TNBC PDX and remain stable during the emergence of docetaxel resistance; however, some genes/pathways were differentially methylated according to docetaxel response. A DNA methylation signature of resistance able to segregate TNBC based on chemotherapy response was identified. Transcriptomic profiling of selected sensitive/resistant pairs and integrative analysis with methylation data demonstrated correlation between some differentially methylated and expressed genes in docetaxel-resistant TNBC PDX models. Multiple gene expression changes were found after the emergence of docetaxel resistance in TNBC. DNA methylation and transcriptional changes identified between docetaxel-sensitive and -resistant TNBC PDX models or residual disease may have predictive value for chemotherapy response in TNBC. IMPLICATIONS: Subtype-specific DNA methylation patterns are maintained in breast cancer PDX models. While no global methylation changes were found, we uncovered differentially DNA methylated and expressed genes/pathways associated with the emergence of docetaxel resistance in TNBC.

Results of switchback from ranibizumab to aflibercept in patients with exudative age-related macular degeneration

Purpose

Intravitreal injection of anti-VEGF drugs has become standard therapy for patients with exudative age-related macular degeneration (AMD). However, some patients do not exhibit sufficient response to the drugs for suppression of choroidal neovascularization activity. We investigated the efficacy of switchback from ranibizumab to aflibercept in patients with AMD who could not achieve further benefit beyond initial therapy of aflibercept injection.

Methods

Eleven eyes of eleven patients were included in this study. Two patients were nonresponders, and nine exhibited tachyphylaxis to aflibercept. All patients received three monthly injections of ranibizumab as an initial phase of switching and received aflibercept as a switchback drug. We investigated changes in injection interval, visual acuity, and central retinal thickness.

Results

In four patients (36.4%), injection interval was extended. The interval was 6.73 weeks before switch and 9.27 weeks after switchback (P=0.96). LogMAR visual acuity was 0.22 before switch and 0.24 after switchback (P=0.62). Central retinal thickness was 306.8 µm before switch and 256.1 after switchback (P=0.13). In all patients who were nonresponders to aflibercept, injection interval could not be extended.

Conclusion

A switchback from ranibizumab to aflibercept may be beneficial in some patients with AMD who exhibit tachyphylaxis to aflibercept.

Chemoresistance in the Human Triple-Negative Breast Cancer Cell Line MDA-MB-231 Induced by Doxorubicin Gradient Is Associated with Epigenetic Alterations in Histone Deacetylase

Chemoresistance is one of the major causes of therapeutic failure in breast cancer patients. In this study, the mechanism of chemoresistance in human triple-negative breast cancer (TNBC) cells (MDA-MB-231) induced by doxorubicin (DOX) gradient was investigated. These DOX-resistant cells showed higher drug efflux rate, increased anchorage-independent growth when cultured in suspension, and increased tumor-forming ability in nude mice, compared to the wild-type MDA-MB-231 cells. RNA sequencing analysis showed an increase in the expression of genes involved in membrane transport, antiapoptosis, and histone regulation. Kaplan-Meier plot analysis of TNBC patients who underwent preoperative chemotherapy showed that the relapse free survival (RFS) of patients with high HIST1H2BK (histone cluster 1 H2B family member k) expression was significantly lower than that of patients with low HIST1H2BK expression. Quantitative real-time PCR confirmed that the level of HIST1H2BK expression was increased in resistant cells. The cytotoxicity analysis showed that the DOX resistance of resistant cells was reduced by treatment with a histone deacetylase (HDAC) inhibitor. Our results suggest that, in DOX-resistant cells, HIST1H2BK expression can be rapidly induced by the high expression of genes involved in membrane transport, antiapoptosis, and histone regulation. In conclusion, chemoresistance in MDA-MB-231 cells can occur in a relatively short period by DOX gradient via this previously known mechanism of resistance, and DOX resistance is dependent on the specificity of resistant cells to HDAC.

Triple-hit therapeutic approach for triple negative breast cancers using docetaxel nanoparticles, EN1-iPeps and RGD peptides

Triple negative breast cancers (TNBC) are aggressive malignancies for which chemotherapy is the only treatment option. Many TNBC acquire chemotherapy resistance, notably docetaxel, which has been associated with the overexpression of transcription factors (TFs), such as ENGRAILED1 (EN1). Here, we have developed a tumor delivery system for docetaxel-PGMA-PAA-nanoparticles and interference peptides designed to specifically inhibit EN1 (EN1-iPeps). To promote tumor specific targeting, we functionalized these nanoparticles with EN1-iPeps engineered with RGD sequences. We found that these peptides reduce cell viability and induce apoptosis in TNBC cells with negligible effects on normal cells (EN1^-). Moreover, EN1-RGD-iPeps-mediated nanoparticle internalization into breast cancer cells was via integrins and intravenous injection of this nanoformulation increased tumor accumulation. Furthermore, docetaxel nanoparticles functionalized with EN1-RGD-iPeps significantly reduced TNBC growth both in vitro and in vivo without showing toxicity. Our results suggest that this targeted nanoformulation represents a new and safe therapeutic approach for chemoresistant TNBCs.

Drug resistance profiling of a new triple negative breast cancer patient-derived xenograft model

Background

Triple-negative breast cancer (TNBC) represents an aggressive subtype with limited therapeutic options. Experimental preclinical models that recapitulate their tumors of origin can accelerate target identification, thereby potentially improving therapeutic efficacy. Patient-derived xenografts (PDXs), due to their genomic and transcriptomic fidelity to the tumors from which they are derived, are poised to improve the preclinical testing of drug-target combinations in translational models. Despite the previous development of breast and TNBC PDX models, those derived from patients with demonstrated health-disparities are lacking.

Methods

We use an aggressive TNBC PDX model propagated in SCID/Beige mice that was established from an African-American woman, TU-BcX-2 K1, and assess its metastatic potential and drug sensitivities under distinct in vitro conditions. Cellular derivatives of the primary tumor or the PDX were grown in 2D culture conditions or grown in mammospheres 3D culture. Flow cytometry and fluorescence staining was used to quantify cancer stem cell-like populations. qRT-PCR was used to describe the mesenchymal gene signature of the tumor. The sensitivity of TU-BcX-2 K1-derived cells to anti-neoplastic oncology drugs was compared in adherent cells and mammospheres. Drug response was evaluated using a live/dead staining kit and crystal violet staining.

Results

TU-BcX-2 K1 has a low propensity for metastasis, reflects a mesenchymal state, and contains a large burden of cancer stem cells. We show that TU-BcX-2 K1 cells have differential responses to cytotoxic and targeted therapies in 2D compared to 3D culture conditions insofar as several drug classes conferred sensitivity in 2D but not in 3D culture, or cells grown as mammospheres.

Conclusions

Here we introduce a new TNBC PDX model and demonstrate the differences in evaluating drug sensitivity in adherent cells compared to mammosphere, or suspension, culture.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5401-2) contains supplementary material, which is available to authorized users.

Novel and Alternative Targets Against Breast Cancer Stemness to Combat Chemoresistance

Breast cancer stem cells (BCSCs) play a vital role in tumor progression and metastasis. They are heterogeneous and inherently radio- and chemoresistant. They have the ability to self-renew and differentiate into non-BCSCs. These determinants of BCSCs including the plasticity between the mesenchymal and epithelial phenotypes often leads to minimal residual disease (MRD), tumor relapse, and therapy failure. By studying the resistance mechanisms in BCSCs, a combinatorial therapy can be formulated to co-target BCSCs and bulk tumor cells. This review addresses breast cancer stemness and molecular underpinnings of how the cancer stemness can lead to pharmacological resistance. This might occur through rewiring of signaling pathways and modulated expression of various targets that support survival and self-renewal, clonogenicity, and multi-lineage differentiation into heterogeneous bulk tumor cells following chemotherapy. We explore emerging novel and alternative molecular targets against BC stemness and chemoresistance involving survival, drug efflux, metabolism, proliferation, cell migration, invasion, and metastasis. Strategic targeting of such vulnerabilities in BCSCs may overcome the chemoresistance and increase the longevity of the metastatic breast cancer patients.