Combined Targeting of Estrogen Receptor Alpha and XPO1 Prevent Akt Activation, Remodel Metabolic Pathways and Induce Autophagy to Overcome Tamoxifen Resistance

Targeting systemic and gut microbial metabolism in ER+ breast cancer

Estrogen receptor-positive (ER+) breast tumors have a better overall prognosis than ER- tumors; however, there is a sustained risk of recurrence. Mounting evidence indicates that genetic and epigenetic changes associated with resistance impact critical signaling pathways governing cell metabolism. This review delves into recent literature concerning the metabolic pathways regulated in ER+ breast tumors by the availability of nutrients and endocrine therapies and summarizes research on how changes in systemic and gut microbial metabolism can affect ER activity and responsiveness to endocrine therapy. As targeting of metabolic pathways using dietary or pharmacological approaches enters the clinic, we provide an overview of the supporting literature and suggest future directions.

XPO1 inhibition displays anti-leukemia efficacy against DNMT3A-mutant acute myeloid leukemia via downregulating glutathione pathway

Acute myeloid leukemia (AML) patients with DNA methyltransferase 3A (DNMT3A) mutation display poor prognosis, and targeted therapy is not available currently. Our previous study identified increased expression of Exportin1 (XPO1) in DNMT3AR882H AML patients. Therefore, we further investigated the therapeutic effect of XPO1 inhibition on DNMT3AR882H AML. Three types of DNMT3AR882H AML cell lines were generated, and XPO1 was significantly upregulated in all DNMT3AR882H cells compared with the wild-type (WT) cells. The XPO1 inhibitor selinexor displayed higher potential in the inhibition of proliferation, promotion of apoptosis, and blockage of the cell cycle in DNMT3AR882H cells than WT cells. Selinexor also significantly inhibited the proliferation of subcutaneous tumors in DNMT3AR882H AML model mice. Primary cells with DNMT3A mutations were more sensitive to selinexor in chemotherapy-naive AML patients. RNA sequencing of selinexor treated AML cells revealed that the majority of metabolic pathways were downregulated after selinexor treatment, with the most significant change in the glutathione metabolic pathway. Glutathione inhibitor L-Buthionine-(S, R)-sulfoximine (BSO) significantly enhanced the apoptosis-inducing effect of selinexor in DNMT3AWT/DNMT3AR882H AML cells. In conclusion, our work reveals that selinexor displays anti-leukemia efficacy against DNMT3AR882H AML via downregulating glutathione pathway. Combination of selinexor and BSO provides novel therapeutic strategy for AML treatment.

Estrogen Receptor Signaling in Breast Cancer

Estrogen receptor (ER) signaling is a critical regulator of cell proliferation, differentiation, and survival in breast cancer (BC) and other hormone-sensitive cancers. In this review, we explore the mechanism of ER-dependent downstream signaling in BC and the role of estrogens as growth factors necessary for cancer invasion and dissemination. The significance of the clinical implications of ER signaling in BC, including the potential of endocrine therapies that target estrogens' synthesis and ER-dependent signal transmission, such as aromatase inhibitors or selective estrogen receptor modulators, is discussed. As a consequence, the challenges associated with the resistance to these therapies resulting from acquired ER mutations and potential strategies to overcome them are the critical point for the new treatment strategies' development.

The role of lncRNA H19 in tumorigenesis and drug resistance of human Cancers

Systemic therapy is one of the most significant cancer treatments. However, drug resistance often appears and has become the primary cause of cancer therapy failure. Regulation of drug target, drug metabolism and drug efflux, cell death escape (apoptosis, autophagy, et al.), epigenetic changes, and many other variables are complicatedly involved in the mechanisms of drug resistance. In various types of cancers, long non-coding RNA H19 (lncRNA H19) has been shown to play critical roles in tumor development, proliferation, metastasis, and multiple drug resistance as well. The efficacy of chemotherapy, endocrine therapy, and targeted therapy are all influenced by the expression of H19, especially in breast cancer, liver cancer, lung cancer and colorectal cancer. Here, we summarize the relationship between lncRNA H19 and tumorigenesis, and illustrate the drug resistance mechanisms caused by lncRNA H19 as well. This review may provide more therapeutic potential targets for future cancer treatments.

The efficacy of selinexor (KPT-330), an XPO1 inhibitor, on non-hematologic cancers: a comprehensive review

PURPOSE

Selinexor is a novel XPO1 inhibitor which inhibits the export of tumor suppressor proteins and oncoprotein mRNAs, leading to cell-cycle arrest and apoptosis in cancer cells. While selinexor is currently FDA approved to treat multiple myeloma, compelling preclinical and early clinical studies reveal selinexor's efficacy in treating hematologic and non-hematologic malignancies, including sarcoma, gastric, bladder, prostate, breast, ovarian, skin, lung, and brain cancers. Current reviews of selinexor primarily highlight its use in hematologic malignancies; however, this review seeks to summarize the recent evidence of selinexor treatment in solid tumors.

METHODS

Pertinent literature searches in PubMed and the Karyopharm Therapeutics website for selinexor and non-hematologic malignancies preclinical and clinical trials.

RESULTS

This review provides evidence that selinexor is a promising agent used alone or in combination with other anticancer medications in non-hematologic malignancies.

CONCLUSION

Further clinical investigation of selinexor treatment for solid malignancies is warranted.

Targeting metabolic adaptations in the breast cancer-liver metastatic niche using dietary approaches to improve endocrine therapy efficacy

Estrogen receptor-positive (ER+) metastatic tumors contribute to nearly 70% of breast cancer-related deaths. Most patients with ER+ metastatic breast cancer (MBC) undergo treatment with the estrogen receptor antagonist fulvestrant (Fulv) as standard-of-care. Yet, among such patients, metastasis in the liver is associated with reduced overall survival compared to other metastasis sites. The factors underlying the reduced responsiveness of liver metastases to ER-targeting agents remain unknown, impeding the development of more effective treatment approaches to improve outcomes for patients with ER+ liver metastases. We therefore evaluated site-specific changes in MBC cells and determined the mechanisms through which the liver metastatic niche specifically influences ER+ tumor metabolism and drug resistance. We characterized ER activity of MBC cells both in vitro, using a novel system of tissue-specific extracellular matrix hydrogels representing the stroma of ER+ tumor metastatic sites (liver, lung and bone), and in vivo, in liver and lung metastasis mouse models. ER+ metastatic liver tumors and MBC cells grown in liver hydrogels displayed upregulated expression of glucose metabolism enzymes in response to Fulv. Furthermore, differential ERα activity, but not expression, was detected in liver hydrogels. In vivo, increased glucose metabolism led to increased glycogen deposition in liver metastatic tumors, while a fasting-mimicking diet increased efficacy of Fulv treatment to reduce the metastatic burden. Our findings identify a novel mechanism of endocrine resistance driven by the liver tumor microenvironment. Implications: These results may guide the development of dietary strategies to circumvent drug resistance in liver metastasis, with potential applicability in other metastatic diseases.

Targeting XPO1-Dependent Nuclear Export in Cancer

Nucleocytoplasmic transport of macromolecules is tightly regulated in eukaryotic cells. XPO1 is a transport factor responsible for the nuclear export of several hundred protein and RNA substrates. Elevated levels of XPO1 and recurrent mutations have been reported in multiple cancers and linked to advanced disease stage and poor survival. In recent years, several novel small-molecule inhibitors of XPO1 were developed and extensively tested in preclinical cancer models and eventually in clinical trials. In this brief review, we summarize the functions of XPO1, its role in cancer, and the latest results of clinical trials of XPO1 inhibitors.

Endocrine resistance in breast cancer: from molecular mechanisms to therapeutic strategies

Estrogen receptor-positive (ER +) breast cancer accounts for approximately 75% of all breast cancers. Endocrine therapies, including selective ER modulators (SERMs), aromatase inhibitors (AIs), and selective ER down-regulators (SERDs) provide substantial clinical benefit by reducing the risk of disease recurrence and mortality. However, resistance to endocrine therapies represents a major challenge, limiting the success of ER + breast cancer treatment. Mechanisms of endocrine resistance involve alterations in ER signaling via modulation of ER (e.g., ER downregulation, ESR1 mutations or fusions); alterations in ER coactivators/corepressors, transcription factors (TFs), nuclear receptors and epigenetic modulators; regulation of signaling pathways; modulation of cell cycle regulators; stress signaling; and alterations in tumor microenvironment, nutrient stress, and metabolic regulation. Current therapeutic strategies to improve outcome of endocrine-resistant patients in clinics include inhibitors against mechanistic target of rapamycin (mTOR), cyclin-dependent kinase (CDK) 4/6, and the phosphoinositide 3-kinase (PI3K) subunit, p110α. Preclinical studies reveal novel therapeutic targets, some of which are currently tested in clinical trials as single agents or in combination with endocrine therapies, such as ER partial agonists, ER proteolysis targeting chimeras (PROTACs), next-generation SERDs, AKT inhibitors, epidermal growth factor receptor 1 and 2 (EGFR/HER2) dual inhibitors, HER2 targeting antibody-drug conjugates (ADCs) and histone deacetylase (HDAC) inhibitors. In this review, we summarize the established and emerging mechanisms of endocrine resistance, alterations during metastatic recurrence, and discuss the approved therapies and ongoing clinical trials testing the combination of novel targeted therapies with endocrine therapy in endocrine-resistant ER + breast cancer patients.

Per- and Polyfluoroalkyl Substance Exposure Combined with High-Fat Diet Supports Prostate Cancer Progression

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals utilized in various industrial settings and include products such as flame retardants, artificial film-forming foams, cosmetics, and non-stick cookware, among others. Epidemiological studies suggest a link between increased blood PFAS levels and prostate cancer incidence, but the mechanism through which PFAS impact cancer development is unclear. To investigate the link between PFAS and prostate cancer, we evaluated the impact of metabolic alterations resulting from a high-fat diet combined with PFAS exposure on prostate tumor progression. We evaluated in vivo prostate cancer xenograft models exposed to perfluorooctane sulfonate (PFOS), a type of PFAS compound, and different diets to study the effects of PFAS on prostate cancer progression and metabolic activity. Metabolomics and transcriptomics were used to understand the metabolic landscape shifts upon PFAS exposure. We evaluated metabolic changes in benign or tumor cells that lead to epigenomic reprogramming and altered signaling, which ultimately increase tumorigenic risk and tumor aggressiveness. Our studies are the first in the field to provide new and clinically relevant insights regarding novel metabolic and epigenetic states as well as to support the future development of effective preventative and therapeutic strategies for PFAS-induced prostate cancers. Our findings enhance understanding of how PFAS synergize with high-fat diets to contribute to prostate cancer development and establish an important basis to mitigate PFAS exposure.

XPO1/CRM1 is a promising prognostic indicator for neuroblastoma and represented a therapeutic target by selective inhibitor verdinexor

BACKGROUND

High-risk neuroblastoma patients have a 5-year survival rate of less than 50%. It's an urgent need to identify new therapeutic targets and the appropriate drugs. Exportin-1 (XPO1), also known as chromosomal region maintenance 1, plays important roles in the progression of tumorigenesis. However, the prognostic and therapeutic values of XPO1 in neuroblastoma have not been reported.

METHODS

Correlations between XPO1 expression level and clinical characteristics were analyzed using the Neuroblastoma Research Consortium (NRC) dataset and tissue microarray analysis. Cell proliferation assays, colony formation assays, apoptosis assays, cell cycle analysis were performed to analyze the anti-tumor effects of verdinexor (KPT-335) in vitro. Western blot and mRNA sequencing were performed to explore underlying mechanism. In vivo anti-tumor effects of verdinexor were studied in a neuroblastoma xenograft model.

RESULTS

Higher XPO1 levels were associated with advanced stage and poor prognosis in neuroblastoma patients. The specific inhibitor of XPO1 verdinexor suppressed the neuroblastoma cell growth both in vitro and in vivo. Specifically, inhibition of XPO1 suppressed the neuroblastoma cell proliferation and induced cell apoptosis by nuclear accumulation of FOXO1 and RB1 in the neuroblastoma due to the inhibition of the PI3K/AKT pathway, and induced G0/G1 phase cell cycle arrest by activation of P53 function.

CONCLUSIONS

XPO1 is a promising prognostic indicator for neuroblastoma and a novel target for antitumor treatment with selective inhibitor verdinexor.

Progress in the Understanding of the Mechanism of Tamoxifen Resistance in Breast Cancer

Tamoxifen is a drug commonly used in the treatment of breast cancer, especially for postmenopausal patients. However, its efficacy is limited by the development of drug resistance. Downregulation of estrogen receptor alpha (ERα) is an important mechanism of tamoxifen resistance. In recent years, with progress in research into the protective autophagy of drug-resistant cells and cell cycle regulators, major breakthroughs have been made in research on tamoxifen resistance. For a better understanding of the mechanism of tamoxifen resistance, protective autophagy, cell cycle regulators, and some transcription factors and enzymes regulating the expression of the estrogen receptor are summarized in this review. In addition, recent progress in reducing resistance to tamoxifen is reviewed. Finally, we discuss the possible research directions into tamoxifen resistance in the future to provide assistance for the clinical treatment of breast cancer.

Combined Targeting of Estrogen Receptor Alpha and Exportin 1 in Metastatic Breast Cancers

The majority of breast cancer specific deaths in women with estrogen receptor positive (ER+) tumors occur due to metastases that are resistant to therapy. There is a critical need for novel therapeutic approaches to achieve tumor regression and/or maintain therapy responsiveness in metastatic ER+ tumors. The objective of this study was to elucidate the role of metabolic pathways that undermine therapy efficacy in ER+ breast cancers. Our previous studies identified Exportin 1 (XPO1), a nuclear export protein, as an important player in endocrine resistance progression and showed that combining selinexor (SEL), an FDA-approved XPO1 antagonist, synergized with endocrine agents and provided sustained tumor regression. In the current study, using a combination of transcriptomics, metabolomics and metabolic flux experiments, we identified certain mitochondrial pathways to be upregulated during endocrine resistance. When endocrine resistant cells were treated with single agents in media conditions that mimic a nutrient deprived tumor microenvironment, their glutamine dependence for continuation of mitochondrial respiration increased. The effect of glutamine was dependent on conversion of the glutamine to glutamate, and generation of NAD+. PGC1α, a key regulator of metabolism, was the main driver of the rewired metabolic phenotype. Remodeling metabolic pathways to regenerate new vulnerabilities in endocrine resistant breast tumors is novel, and our findings reveal a critical role that ERα-XPO1 crosstalk plays in reducing cancer recurrences. Combining SEL with current therapies used in clinical management of ER+ metastatic breast cancer shows promise for treating and keeping these cancers responsive to therapies in already metastasized patients.

[Interaction between PSF and cytokeratin 18 mediates PSF relocation to cell membrane and maintains chemosensitivity of myeloid leukemia]

OBJECTIVE

To identify the chaperone of polypyrimidine tractor-binding protein-associated splicing factor (PSF) in myeloid leukemia cells, and to explore the mechanism and redistributive pattern to cell surface of PSF in chemo-sensitive HL60 cells and resistant HL60/DOX cells.

METHODS

The eukaryotic expression vector of PSF was transfected with liposomes transiently, then flow cytometry was used to detect the expression level of PSF on the cell surface 24 h, 48 h and 72 h after vector transfections. We constructed a chimeric expression vector, streptavidin binding peptide (SBP)-PSF, meanwhile this vector was transfected and made SBP-PSF fusion protein overexpress. In addition, we used streptavidin magnetic beads to precipitate the cellular chaperonin of PSF and then identified its chaperonin by mass spectrometry (MS). Lentiviral vectors containing cytokeratin18 (K18) interference sequences were transfected into 293T cells to prepare lentivirus. HL60 and HL60/DOX cells were infected with lentivirus to obtain stable interfering K18 cell lines. Next, flow cytometry was used to test the membrane relocation level of PSF. Together, these methods confirmed the similar or different mechanisms of the PSF redistributing to membrane synergistically mediated by K18 in HL60 and HL60/DOX cells.

RESULTS

The expression of membrane relocated PSF was detected every day for three days (at the end of 24 h, 48 h and 72 h) after transient overexpression. The expressing rate of PSF on the cell surface was 22.4%±3.5%, 37.9%±6.0%, 58.3%±8.8%, respectively in sensitive HL60 cells, while that was 4.7%±0.5%, 3.9%±0.6%, 2.9%±0.6% , respectively in resistant HL60/DOX cells. The difference of expressing rate on each day was significant, P<0.01. We identified K18 detected by co-immunoprecipitation and mass spectrum assay which was the cellular chaperone of PSF. We found that K18 knockdown decreased the PSF expression level which redistributed on cell surface from 48.9%±5.4% to 6.2%±1.0% in sensitive HL60 cells, and from 9.11%±1.2% to 2.21%±0.51% in resistant HL60/DOX cells, respectively.

CONCLUSION

K18 is the intracellular chaperonin of PSF. The interaction of PSF and K18 mediates its redistribution to cell membrane in sensitive cells. While in resistant cells, PSF failed to relocate at the cell surface and accumulated in cells, which mediated resistance to chemotherapeutics.

XPO1 is a critical player for bortezomib resistance in multiple myeloma: A quantitative proteomic approach

Among the blood cancers, 13% mortality is caused by Multiple myeloma (MM) type of hematological malignancy. In spite of therapeutic advances in chemotherapy treatment, still MM remains an incurable disease is mainly due to emergence of chemoresistance. At present time, FDA approved bortezomib is the first line drug for MM treatment. However, like other chemotherapy, MM patients are acquiring resistance against bortezomib. The present study aims to identify and validate bortezomib resistant protein targets in MM using iTRAQ and label free quantitative proteomic approaches. 112 differentially expressed proteins were commonly found in both approaches with similar differential expression pattern. Exportin-1 (XPO1) protein was selected for further validation as its significant high expression was observed in both iTRAQ and label free analysis. Bioinformatic analysis of these common differentially expressed proteins showed a clear cluster of proteins such as SMC1A, RCC2, CSE1, NUP88, NUP50, TPR, HSPA14, DYNLL1, RAD21 and RANBP2 being associated with XPO1. Functional studies like cell count assay, flow cytometry assay and soft agar assay proved that XPO1 knock down in RPMI 8226R cell line results in re-sensitization to bortezomib drug. The mass spectrometry data are available via ProteomeXchange with identifier PXD013859. BIOLOGICAL SIGNIFICANCE: Multiple myeloma (MM) is a type of hematological malignancy which constitutes about 13% of all blood cell related malignancies. Chemoresistance is one of the major obstacles for the successful treatment for MM. Bortezomib is a first proteasome inhibitor drug, widely used in MM treatment. The present study aims to identify and validate bortezomib resistant protein targets in MM. Here, we identified 112 candidate proteins to be associated with bortezomib resistance using global quantitative proteomic analysis. Among these candidate proteins, we show that XPO1 plays crucial role in emerging bortezomib resistance using functional studies like cell count assay, flow cytometry assay and soft agar assay. XPO1 could be a potential therapeutic target for MM and development of inhibitors of XPO1 might help to cure MM.