[A case of mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN) diagnosed by re-biopsy of the enlarged primary tumor during chemotherapy for gastric adenocarcinoma].

Gastric mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN) is an extremely rare form of gastric neoplasm, and its prognosis is often poor. This is a case report wherein the primary site increased during chemotherapy against gastric adenocarcinoma and was diagnosed with gastric MiNEN after total gastrectomy. A 71-year-old man was diagnosed with gastric adenocarcinoma complicated with liver and para-aortic lymph node metastasis. Chemotherapy with S-1, oxaliplatin, and trastuzumab was initiated. Although the size of metastatic lesions was reduced after six courses of treatment, a part of the primary site of gastric tumor rapidly. Pathological rebiopsy of the primary site suggested a neuroendocrine carcinoma, and he was finally diagnosed with gastric MiNEN after total gastrectomy. Thus, second-line chemotherapy was then initiated showing good response. We herein report a case of MiNEN with a rare diagnostic process.

Resveratrol exhibits diverse anti-cancer activities through epigenetic regulation of E-cadherin and p21 in triple-negative breast cancer cells.

BACKGROUND: Triple-negative breast cancer (TNBC) has an aggressive phenotype and poor outcome, however no specific targeted therapy has been established for TNBC lacking germline BRCA1/2 pathogenic variants. To develop a novel therapeutic strategy, we explored the potential of resveratrol (RSV) for TNBC treatment. METHODS: We investigated the effects of RSV on malignant phenotypes of TNBC cells as well as on apoptosis induced by ABT263, a specific inhibitor of BCL-2 and BCL-xL, using morphological observation, migration assay, ß-galactosidase staining, and Hoechst staining. To elucidate the underlying mechanisms of RSV-mediated effects, expression levels and histone acetylation levels of cadherin 1 (CDH1, E-cadherin) and cyclin dependent kinase inhibitor 1A (CDKN1A, p21) were determined by RT-qPCR, western blotting, and chromatin immunoprecipitation. Furthermore, knockdown analysis was conducted to evaluate the involvement of E-cadherin and/or p21 in RSV potentiation on cytotoxic activity of ABT263. RESULTS: RSV treatment induced epithelial-like cellular morphology and suppressed the migration capacity in MDA-MB-231 and BT-549-Luc TNBC cells. ß-galactosidase-positive cells were increased after RSV treatment, indicating the induction of cellular senescence, in MDA-MB-231 cells but not in BT-549-Luc cells. RSV increased the expression and histone acetylation of CDH1 and CDKN1A in both cells. Interestingly, pre-treatment with RSV enhanced the induction of apoptosis in the ABT263-treated MDA-MB-231 and BT-549-Luc cells, and knockdown of CDKN1A decreased ABT263-induced apoptosis in RSV-treated MDA-MB-231 cells. CONCLUSIONS: RSV represses the metastatic capacity and enhances the cytotoxic activity of ABT263 in TNBC cells. Our results suggested that RSV can potentially be used as a repressor of metastasis or a sensitizer to ABT263 for TNBC treatment via up-regulation of CDH1 and CDKN1A through epigenetic mechanisms.

OLIG2 is an in vivo bookmarking transcription factor in the developing neural tube in mouse.

Cells possess intrinsic features that are inheritable via epigenetic regulation, such as DNA methylation and histone modification. These inheritable features maintain a unique gene expression pattern, underlying cellular memory. Because of the degradation or displacement of mitotic chromosomes, most transcription factors do not contribute to cellular memory. However, accumulating in vitro evidence indicates that some transcription factors can be retained in mitotic chromosomes called as bookmarking. Such transcription factors may contribute to a novel third mechanism of cellular memory. Since most findings of transcription factor bookmarking have been reported in vitro, little is currently known in vivo. In the neural tube of mouse embryos, we discovered that OLIG2, a basic helix loop helix (bHLH) transcription factor that regulates proliferation of neural progenitors and the cell fate of motoneurons and oligodendrocytes, binds to chromatin through every cell cycle including M-phase. OLIG2 chromosomal localization coincides with mitotic cell features such as the phosphorylation of histone H3, KI67, and nuclear membrane breakdown. Chromosomal localization of OLIG2 is regulated by an N-terminus triple serine motif. Photobleaching analysis revealed slow OLIG2 mobility, suggesting a high affinity of OLIG2 to DNA. In Olig2 N-terminal deletion mutant mice, motoneurons and oligodendrocyte progenitor numbers are reduced in the neural tube, suggesting that the bookmarking regulatory domain is important for OLIG2 function. We conclude that OLIG2 is a de novo in vivo bookmarking transcription factor. Our results demonstrate the presence of in vivo bookmarking in a living organism and illustrate a novel function of transcription factors.

Immune profile analysis of peripheral blood and tumors of lung cancer patients treated with immune checkpoint inhibitors.

Background: Immune checkpoint inhibitors (ICIs) have become central to lung cancer drug therapy, and establishing biomarkers that can predict effects and adverse events (AEs) is awaited. We prospectively analyzed the association between the immune-related molecular expression in peripheral blood mononuclear cells (PBMCs) and lung cancer tissues, and the effects of ICI monotherapy. Methods: Twenty-one patients with advanced non-small cell lung cancer (NSCLC) who received ICI monotherapy were included. Changes in the expression of immune-related molecules in PBMCs before and after the administration of ICI were analyzed by flow cytometry. The major histocompatibility complex (MHC) class I and programmed cell death-ligand 1 (PD-L1) expression of cancer cells, and the PD-L1, CD8 and CD103 expression of tumor infiltrating immune cells in lung cancer tissue before the administration of ICI were confirmed by immunohistochemistry (IHC). Results: Twenty-one patients were investigated, including 11 adenocarcinoma and 10 squamous cell carcinoma cases. Anti-programmed cell death protein-1 (PD-1) antibody (n=18) and anti-PD-L1 antibody (n=3) were administered. The clinical responses were graded as follows: complete response (CR) (n=1), partial response (PR) (n=7), stable disease (SD) (n=10) and progressive disease (PD) (n=3). Among immune-related molecules expressed in PBMCs, the CD103+ CD39+ CD8+ T cell change after administration closely correlated with the clinical response. In the univariate analyses of the factors associated with progression-free survival (PFS), CD103+ CD39+ CD8+ cell change after administration was identified as a significant prognostic factor, while the CD103+ CD39+ CD8+ cell change after administration and Brinkman index were independent prognostic factors in a multivariate analysis of the factors associated with PFS. Conclusions: The CD103+ CD39+ CD8+ cell change after administration may predict the efficacy of ICIs.

Establishment of neural stem cell culture from the central nervous system of the Iberian ribbed newt Pleurodeles waltl.

Urodele amphibians have exceptional regeneration ability in various organs. Among these, the Iberian ribbed newt (Pleurodeles waltl) has emerged as a useful model organism for investigating the mechanisms underlying regeneration. Neural stem cells (NSCs) are an important source of regeneration in the central nervous system (CNS) and their culture method in vitro has been well established. NSCs form spherical cell aggregates called neurospheres and their formation has been demonstrated in various vertebrates, including some urodele species, but not in P. waltl. In this study, we reported neurosphere formation in brain- and spinal cord-derived cells of post-metamorphic P. waltl. These neurospheres showed proliferative activity and similar expression of marker proteins. However, the surface morphology was found to vary according to their origin, implying that the characteristics of the neurospheres generated from the brain and spinal cord could be similar but not identical. Subsequent in vitro differentiation analysis demonstrated that spinal cord-derived neurospheres gave rise to neurons and glial cells. We also found that cells in neurospheres from P. waltl differentiated to oligodendrocytes, whereas those from axolotls were reported not to differentiate to this cell type under standard culture conditions. Based on our findings, implantation of genetically modified neurospheres together with associated technical advantages in P. waltl could reveal pivotal gene(s) and/or signaling pathway(s) essential for the complete spinal cord regeneration ability in the future.

Cytoplasmic Polyadenylation Element-Binding Protein 1 Post-transcriptionally Regulates Fragile X Mental Retardation 1 Expression Through 3' Untranslated Region in Central Nervous System Neurons.

Fragile X syndrome (FXS) is an inherited intellectual disability caused by a deficiency in Fragile X mental retardation 1 (Fmr1) gene expression. Recent studies have proposed the importance of cytoplasmic polyadenylation element-binding protein 1 (CPEB1) in FXS pathology; however, the molecular interaction between Fmr1 mRNA and CPEB1 has not been fully investigated. Here, we revealed that CPEB1 co-localized and interacted with Fmr1 mRNA in hippocampal and cerebellar neurons and culture cells. Furthermore, CPEB1 knockdown upregulated Fmr1 mRNA and protein levels and caused aberrant localization of Fragile X mental retardation protein in neurons. In an FXS cell model, CPEB1 knockdown upregulated the mRNA levels of several mitochondria-related genes and rescued the intracellular heat shock protein family A member 9 distribution. These findings suggest that CPEB1 post-transcriptionally regulated Fmr1 expression through the 3' untranslated region, and that CPEB1 knockdown might affect mitochondrial function.

Sulfatide with ceramide composed of phytosphingosine (t18:0) and 2-hydroxy FAs in renal intercalated cells.

Diverse molecular species of sulfatide with differences in FA lengths, unsaturation degrees, and hydroxylation statuses are expressed in the kidneys. However, the physiological functions of specific sulfatide species in the kidneys are unclear. Here, we evaluated the distribution of specific sulfatide species in the kidneys and their physiological functions. Electron microscopic analysis of kidneys of Cst-deficient mice lacking sulfatide showed vacuolar accumulation in the cytoplasm of intercalated cells in the collecting duct, whereas the proximal and distal tubules were unchanged. Immunohistochemical analysis revealed that vacuolar H+-ATPase-positive vesicles were accumulated in intercalated cells in sulfatide-deficient kidneys. Seventeen sulfatide species were detected in the murine kidney by iMScope MALDI-MS analysis. The distribution of the specific sulfatide species was classified into four patterns. Although most sulfatide species were highly expressed in the outer medullary layer, two unique sulfatide species of m/z 896.6 (predicted ceramide structure: t18:0-C22:0h) and m/z 924.6 (predicted ceramide structure: t18:0-C24:0h) were dispersed along the collecting duct, implying expression in intercalated cells. In addition, the intercalated cell-enriched fraction was purified by fluorescence-activated cell sorting using the anti-vacuolar H+-ATPase subunit 6V0A4, which predominantly contained sulfatide species (m/z 896.6 and 924.6). The Degs2 and Fa2h genes, which are responsible for ceramide hydroxylation, were expressed in the purified intercalated cells. These results suggested that sulfatide molecular species with ceramide composed of phytosphingosine (t18:0) and 2-hydroxy FAs, which were characteristically expressed in intercalated cells, were involved in the excretion of NH3 and protons into the urine.

One DNA Methylation Regulates CHIP Gene Expression of Human Breast Cancer and Predicts Recurrence.

BACKGROUND/AIM: Carboxyl terminus of Hsc70-interacting protein (CHIP) is a ubiquitin ligase that induces ubiquitination and degradation of its target proteins including oncoproteins. We reported that its down-regulation is associated with tumor progression and metastasis of breast cancer. However, the mechanism through which CHIP gene affects cancer cells is unclear. MATERIALS AND METHODS: We extracted RNA from 45 primary breast cancer samples and compared CHIP mRNA expression profiles, promoter DNA methylation status, and clinicopathological information. RESULTS: CHIP mRNA expression was significantly correlated with the tumor progression status. In several samples, a pinpoint CpG methylation in the CHIP gene promoter region was significantly correlated with CHIP mRNA expression. When this specific CpG was methylated in estrogen receptor (ER)-positive cases, a significant difference in 5-year recurrence was not found compared with ER-negative cases. CONCLUSION: CpG methylation contributes to the long-term prognosis of ER-positive breast cancer.

Molecular targeted drugs resistance impairs double-strand break repair and sensitizes ER-positive breast cancer to PARP inhibitors.

BACKGROUND: There are various treatments for estrogen-positive breast cancer, mainly hormone therapy and molecular-targeted drugs. Acquiring resistance to these drugs is a major clinical problem. Additionally, little is known about the effect of drug resistance on the DNA repair mechanism. Poly ADP ribose polymerase (PARP) inhibitors currently used for treating HER2-negative metastatic breast cancer with BRCA mutations have been shown to be effective in BRCA-deficient cells with impaired homologous recombination repair. Here, we investigated the effect of drug resistance acquisition on the DNA repair mechanism and the effect of PARP inhibitors on ER (estrogen receptor) -positive breast cancer. METHODS: We investigated changes in the expression of DNA repair mechanism-related factors and repair ability of double-strand breaks (DSB) in various drug-resistant cell lines established in our laboratory. Additionally, PARP inhibitor susceptibility was investigated using olaparib. RESULTS: DSB repairs in MCF-7 and hormone therapy-resistant model cells were normal, and these cells demonstrated low sensitivity to olaparib. The resistant cell lines against CDK4/6 inhibitors, fulvestrant and mTOR/PI3K inhibitors showed decreased DSB repair ability and high olaparib sensitivity. They showed low sensitivity to CDK4/6 inhibitors, a close link between acquiring resistance to CDK4/6 inhibitors and hypersensitivity to olaparib. CONCLUSIONS: Our study suggests some cases of acquiring drug resistance impairs DSB repair ability and sensitizes ER-positive breast cancer to PARP inhibitors.

Cpeb1 expression is post-transcriptionally regulated by AUF1, CPEB1, and microRNAs.

Cytoplasmic polyadenylation element binding protein 1 (CPEB1) regulates the translation of numerous mRNAs. We previously showed that AU-rich binding factor 1 (AUF1) regulates Cpeb1 expression through the 3' untranslated region (3'UTR). To investigate the molecular basis of the regulatory potential of the Cpeb1 3'UTR, here we performed reporter analyses that examined expression levels of Gfp reporter mRNA containing the Cpeb1 3'UTR. Our findings indicate that CPEB1 represses the translation of Cpeb1 mRNA and that miR-145a-5p and let-7b-5p are involved in the reduction in Cpeb1 expression in the absence of AUF1. These results suggest that Cpeb1 expression is post-transcriptionally regulated by AUF1, CPEB1, and microRNAs.

Targeting Amino Acid Metabolic Reprogramming via L-Type Amino Acid Transporter 1 (LAT1) for Endocrine-Resistant Breast Cancer.

The PI3K/Akt/mTOR pathway has been well known to interact with the estrogen receptor (ER)-pathway and to be also frequently upregulated in aromatase inhibitor (AI)-resistant breast cancer patients. Intracellular levels of free amino acids, especially leucine, regulate the mammalian target of rapamycin complex 1 (mTORC1) activation. L-type amino acid transporters such as LAT1 and LAT3 are associated with the uptake of essential amino acids. LAT1 expression could mediate leucine uptake, mTORC1 signaling, and cell proliferation. Therefore, in this study, we explored amino acid metabolism, including LAT1, in breast cancer and clarified the potential roles of LAT1 in the development of therapeutic resistance and the eventual clinical outcome of the patients. We evaluated LAT1 and LAT3 expression before and after neoadjuvant hormone therapy (NAH) and examined LAT1 function and expression in estrogen deprivation-resistant (EDR) breast carcinoma cell lines. Tumors tended to be in advanced stages in the cases whose LAT1 expression was high. LAT1 expression in the EDR cell lines was upregulated. JPH203, a selective LAT1 inhibitor, demonstrated inhibitory effects on cell proliferation in EDR cells. Hormone therapy changed the tumor microenvironment and resulted in metabolic reprogramming through inducing LAT1 expression. LAT1 expression then mediated leucine uptake, enhanced mTORC1 signaling, and eventually resulted in AI resistance. Therefore, LAT1 could be the potential therapeutic target in AI-resistant breast cancer patients.

Distribution, fine structure, and three-dimensional innervation of lamellar corpuscles in rat plantar skin.

Lamellar corpuscles function as mechanoreceptors in the skin, composed of axon terminals and lamellae constructed by terminal Schwann cells. They are classified into Pacinian, Meissner, and simple corpuscles based on histological criteria. Lamellar corpuscles in rat dermal papilla cells have been reported; however, the morphological aspects have yet to be thoroughly investigated. In the present study, we analyzed the enzyme activity, distribution, fine structure, and three-dimensional innervation of lamellar corpuscles in rat plantar skin. The lamellar corpuscles exhibiting non-specific cholinesterase were densely distributed in rat footpads, evident as notable skin elevations, especially at the apex, the highest portion of the ridges in each footpad. In contrast, only a few lamellar corpuscles were found in other plantar skin areas. Lamellar corpuscle was considered composed of a flat axon terminal Schwann cell lamellae, which were roughly concentrically arranged in the dermal papilla. These histological characteristics correspond to those of the simple corpuscle. Moreover, the axon tracing method revealed that one trunk axon innervated several simple corpuscles. The territory of the trunk axons overlapped with each other. Finally, the animals' footprints were analyzed. During the pausing and walking phases, footpads are often in contact with the floor. These results demonstrate that the type of lamellar corpuscles in the dermal papillae of rat plantar skin is a simple corpuscle and implies that their distribution pattern in the plantar skin is convenient for efficient sensing and transmission of mechanical stimuli from the ground.

The nephric mesenchyme lineage of intermediate mesoderm is derived from Tbx6-expressing derivatives of neuro-mesodermal progenitors via BMP-dependent Osr1 function.

In vertebrate embryos, the kidney primordium metanephros is formed from two distinct cell lineages, Wolffian duct and metanephric mesenchyme, which were classically grouped as intermediate mesoderm. Whereas the reciprocal interactions between these two cell populations in kidney development have been studied extensively, the mechanisms generating them remain elusive. Here, we show that the mouse cell lineage that forms nephric mesenchyme develops as a subpopulation of Tbx6-expressing mesodermal precursor derivatives of neuro-mesodermal progenitors (NMPs) under the condition of bone morphogenetic protein (BMP)-signal-dependent Osr1 expression. The Osr1-expressing nephric mesenchyme precursors were confirmed as descendants of NMPs because they were labeled by Sox2 N1 enhancer-EGFP. In Tbx6 mutant embryos, nephric mesenchyme changed its fate into neural tissues, which reflected its NMP origin. In Osr1 mutant embryos, the specific region of the Tbx6-expressing mesoderm precursor, which normally expresses Osr1 and develops into the nephric mesenchyme, instead expressed the somite marker FoxC2. BMP signaling activated Osr1 expression in a region of TBX6-expressing mesoderm and elicited nephric mesenchyme development. This study suggested a new model of cell lineage segregation during gastrulation.

AUF1, an mRNA decay factor, has a discordant role in Cpeb1 expression.

Cytoplasmic polyadenylation element binding protein 1 (CPEB1) regulates polyadenylation and subsequent translation of CPE-containing mRNAs involved in various physiological and pathological phenomena. Although the significance of CPEB1-mediated translational regulation has recently been reported, the detailed regulatory mechanism of Cpeb1 expression remains unclear. To elucidate the post-transcriptional regulatory mechanisms of Cpeb1 expression, we constructed reporter plasmids containing various deletions or mutations in the Cpeb1 mRNA 3' untranslated region (3'UTR). We investigated their expression levels in Neuro2a neuroblastoma cells. We found that Cpeb1 expression is regulated through an AU-rich element in its 3'UTR. Furthermore, the mRNA decay factor AU-rich binding factor 1 (AUF1) regulates Cpeb1 expression, and knockdown of AUF1 upregulates Cpeb1 mRNA expression but results in a decrease in CPEB1 protein levels. These findings indicate that AUF1 has a discordant role in the expression of Cpeb1.

CD4+ Resident Memory T Cells Mediate Long-Term Local Skin Immune Memory of Contact Hypersensitivity in BALB/c Mice.

In allergic contact dermatitis (ACD) and contact hypersensitivity (CHS), the healed skin shows greater swelling than the naïve skin in the same individual upon re-exposure to the same hapten. This "local skin memory" (LSM) in healed skin was maintained for a prolonged period of time and mediated by skin CD8+-resident memory T (TRM) cells in C57BL/6 mice. However, the number of CD4+ T cells is elevated in ACD-healed human skin, and the contribution of CD4+ TRM cells to the formation of LSM currently remains unclear. We herein demonstrated that immediately after CHS subsided, the healed skin in BALB/c mice showed an accumulation of hapten-specific CD4+ and CD8+ TRM cells, with a predominance of CD4+ TRM cells. The presence of CD4+ or CD8+ TRM cells in the healed skin was sufficient for the induction of a flare-up reaction upon a re-challenge. The CD4+ and CD8+ TRM cells both produced interferon-γ and tumor necrosis factor early after the re-challenge. Moreover, while CD8+ TRM cells gradually decreased over time and were eventually lost from the healed skin at 40-51 weeks after the resolution of CHS, the CD4+ TRM cell numbers remained elevated during this period. The present results indicate that the long-term maintenance of LSM is mediated by CD4+ TRM cells, and thus CD4+ TRM cells are an important target for the treatment of recurrent human ACD.

CT and MRI findings of a stromal tumour of uncertain malignant potential of the prostate.

Cystic neoplasms arising from the prostate are rare, and stromal tumours of uncertain malignant potential and the spectrum of cystic epithelial tumours of the prostate are the major differential diagnoses of a cystic prostatic neoplasm. We report a case of a stromal tumour of uncertain malignant potential, which showed a multilocular cystic mass with some solid components. The solid component of the tumour did not show substantial diffusion restriction and uptake of 18F-FDG-PET, and this could be the critical finding suggesting a stromal tumour of uncertain malignant potential rather than a malignant cystic epithelial tumour.

Heregulin controls ERα and HER2 signaling in mammospheres of ERα-positive breast cancer cells and interferes with the efficacy of molecular targeted therapy.

Estrogen receptor (ER)α and the human epidermal growth factor receptor (HER) family are inversely expressed in ERα-positive cancer in association with resistance to hormonal therapy, but the mechanism underlying their relationship remains unknown. We analyzed the effect of HER family ligands on the expression of ER and the HER family in ERα-positive MCF-7 and T47D breast cancer cell lines in 3D spheroid culture. Here, we demonstrated for the first time that heregulin-1ß (HRG), a HER3 and HER4 ligand, most effectively regulated ER/HER family expression by decreasing ERα mRNA expression and increasing HER family mRNA expression. HRG treatment attenuated fulvestrant-mediated growth inhibition, and promoted the migration of MCF-7 cells. Moreover, HRG increased the CD44+/CD24- cell fraction and side population cells, both of which are recognized as prospective breast cancer stem cell markers. HRG activated both phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) and mitogen-activated protein kinase (MAPK) pathways. Inhibitors of these pathways reduced the growth of MCF-7 cells, but the addition of HRG has different effects on these pathways. HRG blocked the inhibitory effect of mTOR inhibitors, such as rapamycin and everolimus, on cell growth but not that of a PI3K inhibitor. Furthermore, HRG slightly decreased the inhibitory effect of an AKT inhibitor on cell growth. In contrast, HRG enhanced the MEK inhibitor-induced inhibition of cell growth. These findings suggest that HRG-stimulated signaling pathways allow ERα-positive breast cancer cells to escape from growth inhibition caused by everolimus, via MAPK signaling and/or other signaling pathways. Everolimus improves progression-free survival in combination with exemestane as second-line therapy for metastatic hormone receptor-positive breast cancer. Our study suggests that HRG is a novel target for ERα-positive breast cancer therapy.

Characterization of a membrane-associated estrogen receptor in breast cancer cells and its contribution to hormone therapy resistance using a novel selective ligand.

The estrogen receptor (ER) plays a role in the progression of hormone-dependent breast cancer and is a hormone therapy target. Estrogen acts as a transcription factor (genomic action) and also produces a quick non-genomic reaction through intracellular signaling pathways. The membrane associated ER (mER) may regulate both these signals and hormone therapy resistance. However, the details remain unclear because a reliable method to distinguish the signals induced by the estradiol (E2)-mER and E2-nuclear ER complex has not been established. In the present study, we prepared the novel ligand Qdot-6-E2, selective for mER, by coupling E2 with insoluble quantum dot nano-beads. We investigated the characteristics of mER signaling pathways and its contribution to hormone therapy resistance using different cell lines including estrogen depletion resistant (EDR) cells with different mechanisms. Qdot-6-E2 stimulated proliferation of nuclear ER-positive cells, but nuclear ER-negative cells showed no response. In addition, Qdot-6-E2 indirectly activated nuclear ER and increased mRNA expression of target genes. We confirmed that E2 was not dissociated from Qdot-6-E2 using a mammalian one-hybrid assay. We visually demonstrated that Qdot-6-E2 acts from the outside of cells. The gene expression profile induced by Qdot-6-E2-mER was different from that induced by E2-nuclear ER. The effect of anti-ER antibody, the GFP-ER fusion protein localization, and the effect of palmitoyl acyltransferase inhibitor also indicated the existence of mER. Regarding intracellular phosphorylation signaling pathways, the MAPK (Erk 1/2) and the PI3K/Akt pathways were both activated by Qdot-6-E2. In EDR cells, only nuclear ER-positive cells showed increased cell proliferation with increased localization of ERα to the membrane fraction. These findings suggested that Qdot-6-E2 reacts with ERα surrounding the cell membrane and that mER signals help the cells to survive under estrogen-depleted conditions by re-localizing the ER to use trace amounts of E2 more effectively. We expect that Qdot-6-E2 is a useful tool for studying the mER.

Decreased ER dependency after acquired resistance to CDK4/6 inhibitors.

BACKGROUND: Cyclin-dependent kinase (CDK) 4/6 inhibitors represent a significant advancement in the treatment of estrogen receptor (ER)-positive human epidermal growth factor receptor 2-negative advanced breast cancer. However, mechanisms of alterations after acquired resistance to CDK4/6 inhibitors and the optimal treatment options are still not established. METHODS: Abemaciclib-resistant cell lines were established from the models of estrogen deprivation-resistant cell lines which retained ER expression and activated ER function derived from MCF-7 breast cancer cell lines. Ribocilib-resistant cell lines were established in the same method as previously reported. RESULTS: Both abemaciclib- and ribociclib-resistant cell lines showed decreased ER expression. ER transcriptional activity was maintained in these cell lines; however, the sensitivity to 4-hydroxytamoxifen and fulvestrant was almost completely lost. These cell lines did not exhibit any ERα gene mutation. Abemaciclib-resistant cell lines demonstrated low sensitivity to other CDK4/6 inhibitors; sensitivities to PI3K inhibitor, mTOR inhibitor, and chemotherapeutic drugs were maintained. CONCLUSIONS: Dependence on ER signaling appears to decrease after the development of acquired resistance to CDK4/6 inhibitors. Further, CDK4/6 inhibitor-resistant cells acquired cross-resistance to other CDK4/6 inhibitors, PI3K/Akt/mTOR inhibitor therapy and chemotherapeutic drugs might serve as optimal treatment options for such breast cancers.