Intrinsic Resistance to 5-Fluorouracil in a Brain Metastatic Variant of Human Breast Cancer Cell Line, MDA-MB-231BR

BCL2A1 and CCL18 Are Predictive Biomarkers of Cisplatin Chemotherapy and Immunotherapy in Colon Cancer Patients

Background: Cisplatin enhances the antitumor T cell response, and the combination of PD-L1 blockade produces a synergistic therapeutic effect. However, the clinical correlation between cisplatin and immunotherapy in colon cancer (CC) is unknown.

Methods: Using the “pRRophetic” package, we calculated the IC50 of cisplatin. The correlation between cisplatin IC50, cisplatin resistance–related genes (CCL18 and BCL2A1), and immunotherapy were preliminarily verified in TCGA and further validated in independent cohorts (GSE39582 and GSE17538), cisplatin-resistant CC cell line DLD1, and our own clinical specimens. Classification performance was evaluated using the AUC value of the ROC curve. Scores of immune signatures, autophagy, ferroptosis, and stemness were quantified using the ssGSEA algorithm.

Results: Based on respective medians of three CC cohorts, patients were divided into high- and low-IC50 groups. Compared with the high IC50 group, the low-IC50 group had significantly higher tumor microenvironment (TME) scores and lower tumor purity. Most co-signaling molecules were upregulated in low IC50 group. CC patients with good immunotherapy efficacy (MSI, dMMR, and more TMB) were more attributable to the low-IC50 group. Among seven shared differentially expressed cisplatin resistance–related genes, CCL18 and BCL2A1 had the best predictive efficacy of the above immunotherapy biomarkers. For wet experimental verification, compared with cisplatin-resistant DLD1, similar to PD-L1, CCL18 and BCL2A1 were significantly upregulated in wild-type DLD1. In our own CC tissues, the mRNA expression of CCL18, BCL2A1, and PD-L1 in dMMR were significantly increased. The high group of CCL18 or BCL2A1 had a higher proportion of MSI, dMMR, and more TMB. IC50, CCL18, BCL2A1, and PD-L1 were closely related to scores of immune-related pathways, immune signatures, autophagy, ferroptosis, and stemness. The microRNA shared by BCL2A1 and PD-L1, hsa-miR-137, were significantly associated with CCL18, BCL2A1, and PD-L1, and downregulated in low-IC50 group. The activity of the TOLL-like receptor signaling pathway affected the sensitivity of CC patients to cisplatin and immunotherapy. For subtype analysis, immune C2, immune C6, HM-indel, HM-SNV, C18, and C20 were equally sensitive to cisplatin chemotherapy and immunotherapy.

Conclusions: CC patients sensitive to cisplatin chemotherapy were also sensitive to immunotherapy. CCL18 and BCL2A1 were novel biomarkers for cisplatin and immunotherapy.

The molecular underpinning of geminin-overexpressing triple-negative breast cancer cells homing specifically to lungs

Triple-negative breast cancer (TNBCs) display lung metastasis tropism. However, the mechanisms underlying this organ-specific pattern remains to be elucidated. We sought to evaluate the utility of blocking extravasation to prevent lung metastasis. To identify potential geminin overexpression-controlled genetic drivers that promote TNBC tumor homing to lungs, we used the differential/suppression subtractive chain (D/SSC) technique. A geminin overexpression-induced lung metastasis gene signature consists of 24 genes was discovered. We validated overexpression of five of these genes (LGR5, HAS2, CDH11, NCAM2, and DSC2) in worsening lung metastasis-free survival in TNBC patients. Our data demonstrate that LGR5-induced β-catenin signaling and stemness in TNBC cells are geminin-overexpression dependent. They also demonstrate for the first-time expression of RSPO2 in mouse lung tissue only and exacerbation of its secretion in the circulation of mice that develop geminin overexpressing/LGR5⁺-TNBC lung metastasis. We identified a novel extravasation receptor complex, consists of CDH11, CD44v6, c-Met, and AXL on geminin overexpressing/LGR5⁺-TNBC lung metastatic precursors, inhibition of any of its receptors prevented geminin overexpressing/LGR5⁺-TNBC lung metastasis. Overall, we propose that geminin overexpression in normal mammary epithelial (HME) cells promotes the generation of TNBC metastatic precursors that home specifically to lungs by upregulating LGR5 expression and promoting stemness, intravasation, and extravasation in these precursors. Circulating levels of RSPO2 and OPN can be diagnostic biomarkers to improve risk stratification of metastatic TNBC to lungs, as well as identifying patients who may benefit from therapy targeting geminin alone or in combination with any member of the newly discovered extravasation receptor complex to minimize TNBC lung metastasis.

HIF and COX-2 expression in triple negative breast cancer cells with hypoxia and 5-fluorouracil

Our purpose was to understand the effects of normoxia or hypoxia on 5-fluorouracil (5-FU) treatment in triple negative breast cancer (TNBC) cells, and characterize the molecular changes in hypoxia inducible factors (HIFs) and cyclooxygenase-2 (COX-2) following treatment. Cell viability and protein levels of HIFs and COX-2 were determined after wild type and HIF silenced MDA-MB-231 cells, and wild type SUM-149 cells, were treated with 5-FU under normoxia or hypoxia. 5-FU reduced cell viability to the same levels irrespective of normoxia or hypoxia. HIF silenced MDA-MB-231 cells showed comparable changes in cell viability, supporting observations that hypoxia and the HIF pathways did not significantly influence cell viability reduction by 5-FU. Our data suggest that HIF-2α accumulation may predispose cancer cells to cell death under hypoxia. SUM-149 cells that have higher COX-2 and HIF-2α following 24 h of hypoxia, were more sensitive to 96 h of hypoxia compared to MDA-MB-231 cells, and were more sensitive to 5-FU than MDA-MB-231 cells. COX-2 levels changed with hypoxia and with 5-FU treatment but patterns were different between the two cell lines. At 96 h, COX-2 increased in both untreated and 5-FU treated cells under hypoxia in MDA-MB-231 cells. In SUM-149 cells, only treatment with 5-FU increased COX-2 at 96 h of hypoxia. Cells that survive hypoxia and 5-FU treatment may exhibit a more aggressive phenotype. Our results support understanding interactions between HIF and COX-2 with chemotherapeutic agents under normoxia and hypoxia, and investigating the use of COX-2 inhibitors in these settings.

Role of ARID1A in epithelial‑mesenchymal transition in breast cancer and its effect on cell sensitivity to 5‑FU

The loss of function mutation of AT‑rich interactive domain 1A (ARID1A) often occurs in patients with breast cancer. It has been found that ARID1A knockout can enhance both the migratory activity of renal carcinoma cells and their sensitivity to therapeutic drugs by promoting epithelial-mesenchymal transition (EMT); however, its mechanisms of action in breast cancer remain unclear. In the present study, immunohistochemistry and reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) revealed that the expression of ARID1A in breast cancer tissues was significantly lower than that in paracancerous tissues, and patients with a low ARID1A expression had a lower survival rate. ARID1A was expressed at low levels in breast cancer cells. In addition, siRNA targeting ARID1A (siARID1A) and ARID1A overexpression vector were transfected into MCF7 and MDA‑MB‑231 cells, respectively. Proliferation assay revealed that ARID1A silencing increased cell viability and partially reversed the inhibitory effects of 5‑fluorouracil (5‑FU) on the MCF7 cells, while ARID1A overexpression exerted an opposite effect on the MDA‑MB‑231 cells. ARID1A silencing promoted proliferation, migration, invasion and angiogenesis, and partly reversed the inhibitory effects of 5‑FU on cell biological behaviors, while the overexpression of ARID1A further enhanced the inhibitory effect of 5‑FU on the cells. Furthermore, ARID1A regulated the migration and invasion of breast cancer cells through EMT. On the whole, the findings of the present study demonstrate that ARID1A exerts an antitumor effect on breast cancer, and its overexpression can enhance the sensitivity of breast cancer cells to 5‑FU.

Synergistic Interactions of 5-Fluorouracil with Inhibitors of Protein Kinase CK2 Correlate with p38 MAPK Activation and FAK Inhibition in the Triple-Negative Breast Cancer Cell Line

Background: The combination effect of 5-fluorouracil (5-FU) with either CX-4945 or a new inhibitor of protein kinase CK2, namely 14B (4,5,6,7-tetrabromo-1-(3-bromopropyl)-2-methyl-1H-benzimidazole), on the viability of MCF-7 and triple-negative MDA-MB-231 breast cancer cell lines was studied. Methods: Combination index (CI) values were determined using an MTT-based assay and the Chou-Talalay model. The effect of the tested drug combinations on pro-apoptotic properties and cell cycle progression was examined using flow cytometry. The activation of FAK, p38 MAPK, and ERK1/2 kinases and the expression of selected pro-apoptotic markers in MDA-MB-231 cell line after the combined treatment were evaluated by the western blot method. Confocal microscopy was used to examine actin network in MDA-MB-231. Results: Our results showed that a synergistic effect (CI < 1) occurred in MDA-MB-231 after treatment with both combinations of 5-FU with 14B or CX-4945, whereas the combination of 5-FU and 14B evoked an antagonistic effect in MCF-7. We conclude that the synergistic interactions (CI < 1) observed for both the combinations of 5-FU and 14B or CX-4945 in MDA-MB-231 correlated with an activation of p38 MAPK, inhibition of FAK, increased expression of apoptogenic markers, prolongation of S-phase of cell cycle, and destabilization of actin network. Conclusions: The obtained results support the recent observation that CK2 inhibitors can improve 5-FU-based anticancer therapy and FAK kinase can be an attractive molecular target in breast cancer therapy.

Knockdown delta-5-desaturase in breast cancer cells that overexpress COX-2 results in inhibition of growth, migration and invasion via a dihomo-γ-linolenic acid peroxidation dependent mechanism

Background

Cyclooxygenase-2 (COX-2), the inducible COX form, is a bi-functional membrane-bound enzyme that typically metabolizes arachidonic acid (downstream ω-6 fatty acid) to form 2-series of prostaglandins known to be involved in cancer development. Overexpression of COX-2 has been found in a majority of breast carcinomas, and has also been associated with increased severity and the development of the metastasis. Our lab recently demonstrated that COX-2 can also metabolize dihomo-γ-linolenic acid (DGLA, a precursor of ω-6 arachidonic acid) to produce an anti-cancer byproduct, 8-hydroxyoctanoic acid (8-HOA) that can inhibit growth and migration of colon and pancreatic cancer cells. We thus tested whether our strategy of knocking down delta-5-desaturase (D5D, the key enzyme that converts DGLA to arachidonic acid) in breast cancer cells overexpressing COX-2 can also be used to promote 8-HOA formation, thereby suppressing cancer growth, migration, and invasion.

Methods

SiRNA and shRNA transfection were used to knock down D5D expression in MDA-MB 231 and 4 T1 cells (human and mouse breast cancer cell lines expressing high COX-2, respectively). Colony formation assay, FITC Annexin V/PI double staining, wound healing and transwell assay were used to assess the effect of our strategy on inhibition of cancer growth, migration, and invasion. GC/MS was used to measure endogenous 8-HOA, and western blotting was performed to evaluate the altered key protein expressions upon the treatments.

Results

We demonstrated that D5D knockdown licenses DGLA to inhibit growth of breast cancer cells via promoting formation of 8-HOA that can inhibit histone deacetylase and activate cell apoptotic proteins, such as procaspase 9 and PARP. Our strategy can also significantly inhibit cancer migration and invasion, associated with altered expression of MMP-2/− 9, E-cadherin, vimentin and snail. In addition, D5D knockdown and DGLA supplementation greatly enhanced the efficacy of 5-fluorouracil on breast cancer growth and migration.

Conclusions

Consistent to our previous studies on colon and pancreatic cancer, here we demonstrate again that the high level of COX-2 in breast cancer cells can be capitalized on inhibiting cancer growth and migration. The outcome of this translational research could guide us to develop new anti-cancer strategy and/or to improve current chemotherapy for breast cancer treatment.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4250-8) contains supplementary material, which is available to authorized users.

Assessment of cytosolic free calcium changes during ceramide-induced cell death in MDA-MB-231 breast cancer cells expressing the calcium sensor GCaMP6m

Alterations in Ca²⁺ signaling can regulate key cancer hallmarks such as proliferation, invasiveness and resistance to cell death. Changes in the regulation of intracellular Ca²⁺ and specific components of Ca²⁺ influx are a feature of several cancers and/or cancer subtypes, including the basal-like breast cancer subtype, which has a poor prognosis. The development of genetically encoded calcium indicators, such as GCaMP6, represents an opportunity to measure changes in intracellular free Ca²⁺ during processes relevant to breast cancer progression that occur over long periods (e.g. hours), such as cell death. This study describes the development of a MDA-MB-231 breast cancer cell line stably expressing GCaMP6m. The cell line retained the key features of this aggressive basal-like breast cancer cell line. Using this model, we defined alterations in relative cytosolic free Ca²⁺ ([Ca²⁺]_CYT) when the cells were treated with C2-ceramide. Cell death was measured simultaneously via assessment of propidium iodide permeability. Treatment with ceramide produced delayed and heterogeneous sustained increases in [Ca²⁺]_CYT. Where cell death occurred, [Ca²⁺]_CYT increases preceded cell death. The sustained increases in [Ca²⁺]_CYT were not related to the rapid morphological changes induced by ceramide. Silencing of the plasma membrane Ca²⁺ ATPase isoform 1 (PMCA1) was associated with an augmentation in ceramide-induced increases in [Ca²⁺]_CYT and also cell death. This work demonstrates the utility of GCaMP6 Ca²⁺ indicators for investigating [Ca²⁺]_CYT changes in breast cancer cells during events relevant to tumor progression, which occur over hours rather than minutes.

In-depth phenotypic characterization of multicellular tumor spheroids: Effects of 5-Fluorouracil

MultiCellular Tumor Spheroids (MCTS), which mimic the 3-Dimensional (3D) organization of a tumor, are considered as better models than conventional cultures in 2-Dimensions (2D) to study cancer cell biology and to evaluate the response to chemotherapeutic drugs. A real time and quantitative follow-up of MCTS with simple and robust readouts to evaluate drug efficacy is still missing. Here, we evaluate the chemotherapeutic drug 5-Fluorouracil (5-FU) response on the growth and integrity of MCTS two days after treatment of MCTS and for three colorectal carcinoma cell lines with different cohesive properties (HT29, HCT116 and SW480). We found different sensitivity to 5-FU for the three CRC cell lines, ranging from high (SW480), intermediate (HCT116) and low (HT29) and the same hierarchy of CRC cell lines sensitivity is conserved in 2D. We also evidence that 5-FU has a strong impact on spheroid cohesion, with the apparition of a number of single detaching cells from the spheroid in a 5-FU dose- and cell line-dependent manner. We propose an innovative methodology for the chemosensitivity evaluation in 3D MCTS that recapitulates and regionalizes the 5-FU-induced changes within MCTS over time. These robust phenotypic read-outs could be easily scalable for high-throughput drug screening that may include different types of cancer cells to take into account tumor heterogeneity and resistance to treatment.

pH responsive N-succinyl chitosan/Poly (acrylamide-co-acrylic acid) hydrogels and in vitro release of 5-fluorouracil

There has been significant progress in the last few decades in addressing the biomedical applications of polymer hydrogels. Particularly, stimuli responsive hydrogels have been inspected as elegant drug delivery systems capable to deliver at the appropriate site of action within the specific time. The present work describes the synthesis of pH responsive semi-interpenetrating network (semi-IPN) hydrogels of N-succinyl-chitosan (NSC) via Schiff base mechanism using glutaraldehyde as a crosslinking agent and Poly (acrylamide-co-acrylic acid)(Poly (AAm-co-AA)) was embedded within the N-succinyl chitosan network. The physico-chemical interactions were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and field emission scanning electron microscope (FESEM). The synthesized hydrogels constitute porous structure. The swelling ability was analyzed in physiological mediums of pH 7.4 and pH 1.2 at 37°C. Swelling properties of formulations with various amounts of NSC/ Poly (AAm-co-AA) and crosslinking agent at pH 7.4 and pH 1.2 were investigated. Hydrogels showed higher swelling ratios at pH 7.4 while lower at pH 1.2. Swelling kinetics and diffusion parameters were also determined. Drug loading, encapsulation efficiency, and in vitro release of 5-fluorouracil (5-FU) from the synthesized hydrogels were observed. In vitro release profile revealed the significant influence of pH, amount of NSC, Poly (AAm-co-AA), and crosslinking agent on the release of 5-FU. Accordingly, rapid and large release of drug was observed at pH 7.4 than at pH 1.2. The maximum encapsulation efficiency and release of 5-FU from SP2 were found to be 72.45% and 85.99%, respectively. Kinetics of drug release suggested controlled release mechanism of 5-FU is according to trend of non-Fickian. From the above results, it can be concluded that the synthesized hydrogels have capability to adapt their potential exploitation as targeted oral drug delivery carriers.

Endocan as a prognostic biomarker of triple-negative breast cancer

PURPOSE

Triple-negative breast cancer (TNBC) has aggressive characteristics and fewer treatment options than other subtypes. The purpose of this study was to explore prognostic biomarkers for TNBC that can be easily detected from the blood samples.

METHODS

MDA-MB-231 and MDA-MB-231BR, a brain metastatic variant of the human TNBC cell line MDA-MB-231, were used as less and more aggressive models of TNBC, respectively. The extent to which the candidate gene/protein identified by RNA sequencing correlated well with aggressiveness of TNBC and how much protein was detected from the blood of tumor-bearing mice were evaluated.

RESULTS

Both the in vitro proliferation and in vivo tumor growth of MDA-MB-231BR were more rapid than those of MDA-MB-231. RNA sequencing identified ESM1 as a gene that was expressed significantly more in MDA-MB-231BR than in MDA-MB-231, and qRT-PCR confirmed a significantly higher expression of ESM1 in MDA-MB-231BR xenograft in vivo. Furthermore, Kaplan-Meier analysis of relapse-free survival demonstrated that TNBC patients with high ESM1 expression had clearly worse relapse-free survival than those with low ESM1 expression, which was consistent with our preclinical findings. Endocan, a protein of ESM1 gene product, was successfully detected in both conditioned medium from MDA-MB-231BR and plasma samples from mice bearing MDA-MB-231BR xenograft, which showed a significantly distinct pattern from less aggressive MDA-MB-231. Moreover, bisulfite sequence analysis revealed that overexpression of ESM1 in MDA-MB-231BR might be attributed to DNA demethylation in an upstream region of the ESM1 gene.

CONCLUSION

This study indicates that endocan could be used as a blood-based prognostic biomarker in TNBC patients.