Induction of endoplasmic reticulum stress by sorafenib and activation of NF-κB by lestaurtinib as a novel resistance mechanism in Hodgkin lymphoma cell lines

C/EBPα-p30 confers AML cell susceptibility to the terminal unfolded protein response and resistance to Venetoclax by activating DDIT3 transcription

BACKGROUND

Acute myeloid leukemia (AML) with biallelic (CEBPAbi) as well as single mutations located in the bZIP region is associated with a favorable prognosis, but the underlying mechanisms are still unclear. Here, we propose that two isoforms of C/EBPα regulate DNA damage-inducible transcript 3 (DDIT3) transcription in AML cells corporately, leading to altered susceptibility to endoplasmic reticulum (ER) stress and related drugs.

METHODS

Human AML cell lines and murine myeloid precursor cell line 32Dcl3 cells were infected with recombinant lentiviruses to knock down CEBPA expression or over-express the two isoforms of C/EBPα. Quantitative real-time PCR and western immunoblotting were employed to determine gene expression levels. Cell apoptosis rates were assessed by flow cytometry. CFU assays were utilized to evaluate the differentiation potential of 32Dcl3 cells. Luciferase reporter analysis, ChIP-seq and ChIP-qPCR were used to validate the transcriptional regulatory ability and affinity of each C/EBPα isoform to specific sites at DDIT3 promoter. Finally, an AML xenograft model was generated to evaluate the in vivo therapeutic effect of agents.

RESULTS

We found a negative correlation between CEBPA expression and DDIT3 levels in AML cells. After knockdown of CEBPA, DDIT3 expression was upregulated, resulting in increased apoptotic rate of AML cells induced by ER stress. Cebpa knockdown in mouse 32Dcl3 cells also led to impaired cell viability due to upregulation of Ddit3, thereby preventing leukemogenesis since their differentiation was blocked. Then we discovered that the two isoforms of C/EBPα regulate DDIT3 transcription in the opposite way. C/EBPα-p30 upregulated DDIT3 transcription when C/EBPα-p42 downregulated it instead. Both isoforms directly bound to the promoter region of DDIT3. However, C/EBPα-p30 has a unique binding site with stronger affinity than C/EBPα-p42. These findings indicated that balance of two isoforms of C/EBPα maintains protein homeostasis and surveil leukemia, and at least partially explained why AML cells with disrupted C/EBPα-p42 and/or overexpressed C/EBPα-p30 exhibit better response to chemotherapy stress. Additionally, we found that a low C/EBPα p42/p30 ratio induces resistance in AML cells to the BCL2 inhibitor venetoclax since BCL2 is a major target of DDIT3. This resistance can be overcome by combining ER stress inducers, such as tunicamycin and sorafenib in vitro and in vivo.

CONCLUSION

Our results indicate that AML patients with a low C/EBPα p42/p30 ratio (e.g., CEBPAbi) may not benefit from monotherapy with BCL2 inhibitors. However, this issue can be resolved by combining ER stress inducers.

TrkA Co-Receptors: The Janus Face of TrkA?

Larotrectinib and Entrectinib are specific pan-Trk tyrosine kinase inhibitors (TKIs) approved by the Food and Drug Administration (FDA) in 2018 for cancers with an NTRK fusion. Despite initial enthusiasm for these compounds, the French agency (HAS) recently reported their lack of efficacy. In addition, primary and secondary resistance to these TKIs has been observed in the absence of other mutations in cancers with an NTRK fusion. Furthermore, when TrkA is overexpressed, it promotes ligand-independent activation, bypassing the TKI. All of these clinical and experimental observations show that genetics does not explain all therapeutic failures. It is therefore necessary to explore new hypotheses to explain these failures. This review summarizes the current status of therapeutic strategies with TrkA inhibitors, focusing on the mechanisms potentially involved in these failures and more specifically on the role of TrkA.

CD30L is involved in the regulation of the inflammatory response through inducing homing and differentiation of monocytes via CCL2/CCR2 axis and NF-κB pathway in mice with colitis

The pathogenesis of inflammatory bowel diseases (IBD) is complex, and dysregulated immune responses play a pivotal role in its occurrence and development. Our previous studies indicated that CD30L may participate in monocyte-mediated inflammation in patients with UC through the activation of circulating monocytes. However, it remains unclear how CD30L participates in monocyte-mediated inflammation in IBD by activation of circulating monocytes. In this study, we observed an increase in the expression of CD30L and chemokine receptor type 2 (CCR2) on circulating monocytes and pro-inflammatory monocytes in the colon lamina propria in mice with dextran sulfate sodium salt (DSS)-induced colitis. Moreover, there was a positive correlation between the expression levels of CCR2 and CD30L (r = 0.8817, p = 0.0480) in monocytes. In Cd30l^-/- mice with DSS-induced colitis, the percentage and absolute number of circulating monocytes and pro-inflammatory monocytes decreased with the downregulation of CCR2. Stimulation via CD30L by immobilized anti-CD30L mAb suppressed the expression of pNF-κB p65, pIκBα, p65 and CCR2 and up-regulated the expression of IκBα in the sorted pro-inflammatory monocytes in Cd30l^-/- mice with DSS-induced colitis. The mRNA levels of Ccr2 in the sorted pro-inflammatory monocytes were significantly down-regulated with the presence of immobilized RM153 and inhibitors of NF-κB (BAY 11-7082) in WT mice with DSS-induced colitis. Our results suggested that CD30L could promote the inflammatory response by inducing the homing and differentiation of monocytes via the chemokine ligand 2 (CCL2)/CCR2 axis and NF-κB signaling pathway in mice with colitis. These findings provide a novel target for monocyte-based immunotherapy against IBD.

KRAS and RAS-MAPK Pathway Deregulation in Mature B Cell Lymphoproliferative Disorders

KRAS mutations account for the most frequent mutations in human cancers, and are generally correlated with disease aggressiveness, poor prognosis, and poor response to therapies. KRAS is required for adult hematopoiesis and plays a key role in B cell development and mature B cell proliferation and survival, proved to be critical for B cell receptor-induced ERK pathway activation. In mature B cell neoplasms, commonly seen in adults, KRAS and RAS-MAPK pathway aberrations occur in a relevant fraction of patients, reaching high recurrence in some specific subtypes like multiple myeloma and hairy cell leukemia. As inhibitors targeting the RAS-MAPK pathway are being developed and improved, it is of outmost importance to precisely identify all subgroups of patients that could potentially benefit from their use. Herein, we review the role of KRAS and RAS-MAPK signaling in malignant hematopoiesis, focusing on mature B cell lymphoproliferative disorders. We discuss KRAS and RAS-MAPK pathway aberrations describing type, incidence, mutual exclusion with other genetic abnormalities, and association with prognosis. We review the current therapeutic strategies applied in mature B cell neoplasms to counteract RAS-MAPK signaling in pre-clinical and clinical studies, including most promising combination therapies. We finally present an overview of genetically engineered mouse models bearing KRAS and RAS-MAPK pathway aberrations in the hematopoietic compartment, which are valuable tools in the understanding of cancer biology and etiology.

Mesencephalic Astrocyte-Derived Neurotrophic Factor, a Prognostic Factor of Cholangiocarcinoma, Affects Sorafenib Sensitivity of Cholangiocarcinoma Cells by Deteriorating ER Stress

Purpose

Intrahepatic cholangiocarcinoma (ICC) is an aggressive malignant tumor characterized by high malignancy and poor prognosis. Although the efficacy of sorafenib against cholangiocarcinoma cell lines has been demonstrated in vivo and in vitro, limited clinical data are available on the efficacy of sorafenib in patients with cholangiocarcinoma. Sorafenib can enhance endoplasmic reticulum (ER) stress-mediated apoptosis, and ER stress and unfolded protein response are also the mechanisms by which cancer cells resist drug therapy. Mesencephalic astrocyte-derived neurotrophic factor (MANF), initially identified as a neurotrophic factor, can be regulated by ER stress activation. There are no available studies on the diagnostic value and therapeutic significance of MANF in ICC. Hence, the purpose of this study was to evaluate the role of MANF in cholangiocarcinoma, investigating the possibility of whether sorafenib could become a reliable strategy for cholangiocarcinoma therapy.

Methods

In this study, the expression level of MANF in ICC patients was investigated by bioinformatic analysis and the results were verified by tissue microarray assay. Cholangiocarcinoma cell lines were also used to determine how MANF regulates the therapeutic effect of sorafenib and to identify the underlying mechanisms.

Results

The results showed that MANF was correlated with poor prognosis and MANF knockdown could facilitate sorafenib-mediated apoptosis and increase the sensitivity of sorafenib treatment by activating excessive ER stress.

Conclusion

MANF is a prognostic marker of cholangiocarcinoma. MANF knockdown increases sorafenib-mediated ER stress and apoptosis in the cholangiocarcinoma cell lines. This mechanism may lead to a new therapeutic strategy in cholangiocarcinoma.

Metabolic implication of tigecycline as an efficacious second-line treatment for sorafenib-resistant hepatocellular carcinoma

Sorafenib represents the current standard of care for patients with advanced-stage hepatocellular carcinoma (HCC). However, acquired drug resistance occurs frequently during therapy and is accompanied by rapid tumor regrowth after sorafenib therapy termination. To identify the mechanism of this therapy-limiting growth resumption, we established robust sorafenib resistance HCC cell models that exhibited mitochondrial dysfunction and chemotherapeutic crossresistance. We found a rapid relapse of tumor cell proliferation after sorafenib withdrawal, which was caused by renewal of mitochondrial structures alongside a metabolic switch toward high electron transport system (ETS) activity. The translation-inhibiting antibiotic tigecycline impaired the biogenesis of mitochondrial DNA-encoded ETS subunits and limited the electron acceptor turnover required for glutamine oxidation. Thereby, tigecycline prevented the tumor relapse in vitro and in murine xenografts in vivo. These results offer a promising second-line therapeutic approach for advanced-stage HCC patients with progressive disease undergoing sorafenib therapy or treatment interruption due to severe adverse events.

Hexokinase-II Inhibition Synergistically Augments the Anti-tumor Efficacy of Sorafenib in Hepatocellular Carcinoma

This study aimed to examine whether inhibition of hexokinase (HK)-II activity enhances the efficacy of sorafenib in in-vivo models of hepatocellular carcinoma (HCC), and to evaluate the prognostic implication of HK-II expression in patients with HCC. We used 3-bromopyruvate (3-BP), a HK-II inhibitor to target HK-II. The human HCC cell line was tested as both subcutaneous and orthotopic tumor xenograft models in BALB/c nu/nu mice. The prognostic role of HK-II was evaluated in data from HCC patients in The Cancer Genome Atlas (TCGA) database and validated in patients treated with sorafenib. Quantitative real-time PCR, western blot analysis, and immunohistochemical staining revealed that HK-II expression is upregulated in the presence of sorafenib. Further analysis of the endoplasmic reticulum-stress network model in two different murine HCC models showed that the introduction of additional stress by 3-BP treatment synergistically increased the in vivo/vitro efficacy of sorafenib. We found that HCC patients with increased HK-II expression in the TCGA database showed poor overall survival, and also confirmed similar results for TCGA database HCC patients who had undergone sorafenib treatment. These results suggest that HK-II is a promising therapeutic target to enhance the efficacy of sorafenib and that HK-II expression might be a prognostic factor in HCC.

The Role of the ER-Induced UPR Pathway and the Efficacy of Its Inhibitors and Inducers in the Inhibition of Tumor Progression

Cancer is the second most frequent cause of death worldwide. It is considered to be one of the most dangerous diseases, and there is still no effective treatment for many types of cancer. Since cancerous cells have a high proliferation rate, it is pivotal for their proper functioning to have the well-functioning protein machinery. Correct protein processing and folding are crucial to maintain tumor homeostasis. Endoplasmic reticulum (ER) stress is one of the leading factors that cause disturbances in these processes. It is induced by impaired function of the ER and accumulation of unfolded proteins. Induction of ER stress affects many molecular pathways that cause the unfolded protein response (UPR). This is the way in which cells can adapt to the new conditions, but when ER stress cannot be resolved, the UPR induces cell death. The molecular mechanisms of this double-edged sword process are involved in the transition of the UPR either in a cell protection mechanism or in apoptosis. However, this process remains poorly understood but seems to be crucial in the treatment of many diseases that are related to ER stress. Hence, understanding the ER stress response, especially in the aspect of pathological consequences of UPR, has the potential to allow us to develop novel therapies and new diagnostic and prognostic markers for cancer.

Stressed Out - Therapeutic Implications of ER Stress Related Cancer Research

The unfolded protein response (UPR) is an established and well-studied cellular response to the stress and serves to relieve the stress and reinstate cellular homeostasis. It occurs in the endoplasmic reticulum (ER), responsible of properly folding and processing of secretory and transmembrane proteins. It is extremely sensitive to alteration in homeostasis caused by various internal or external stressors which leads to accumulation of misfolded or unfolded proteins in the ER lumen. The UPR works by restoring protein homeostasis in the ER, either through the boosting of protein-folding and degradation capability or by assuaging the demands for such effects, and can cause the activation of cell death if unable to do so. Cancer cells have adapted to gain advantage from the UPR and keeping the cell away from apoptosis and promoting survival, including survival of the cancer stem cells and evading the immune system. Several components of the UPR are overexpressed in a malignant cell and are responsible for resistance from various chemotherapy options and radiotherapy, which are also responsible for causing ER stress and activating the UPR. In this review, we discuss the various ways in which UPR can aid different cancers to survive and evade therapy and highlight recent research, which exploits the UPR to confer sensitivity to these cancer cells against various drugs and radiation.

The interaction of sorafenib and regorafenib with membranes is modulated by their lipid composition

Sorafenib and regorafenib are small-molecule kinase inhibitors approved for the treatment of locally recurrent or metastatic, progressive, differentiated thyroid carcinoma, renal cell carcinoma, and hepatocellular carcinoma (sorafenib) and of colorectal cancer (regorafenib). As of now, the mechanisms, which are responsible for their antitumor activities, are not completely understood. Given the lipophilic nature of the molecules, it can be hypothesized that the pharmacological impact is mediated by the interaction with cellular membranes as it is true for many pharmacologically active molecules. However, an interaction of sorafenib or regorafenib with lipid membranes has not yet been investigated in detail. Here, we characterized the interaction of both drugs with lipid membranes by applying a variety of biophysical approaches including nuclear magnetic resonance, electron spin resonance, and fluorescence spectroscopy. We found that sorafenib and regorafenib bind to lipid membranes by inserting into the lipid-water interface of the bilayer. This membrane embedding causes a disturbance of bilayer structure leading to an increased permeability of the membrane for polar molecules. One approach shows that the extent of the effects depends on the membrane lipid composition underlining a particular role of phosphatidylcholine and cholesterol. Our data for the first time characterize the impact of sorafenib and regorafenib on the lipid membrane structure and dynamics, which may contribute to a better understanding of their effectiveness in the treatment of malignancies as well as of their side effects.

Aberrant Lipid Metabolism Promotes Prostate Cancer: Role in Cell Survival under Hypoxia and Extracellular Vesicles Biogenesis

Prostate cancer (PCa) is the leading malignancy among men in United States. Recent studies have focused on the identification of novel metabolic characteristics of PCa, aimed at devising better preventive and therapeutic approaches. PCa cells have revealed unique metabolic features such as higher expression of several enzymes associated with de novo lipogenesis, fatty acid up-take and β-oxidation. This aberrant lipid metabolism has been reported to be important for PCa growth, hormone-refractory progression and treatment resistance. Furthermore, PCa cells effectively use lipid metabolism under adverse environmental conditions for their survival advantage. Specifically, hypoxic cancer cells accumulate higher amount of lipids through a combination of metabolic alterations including high glutamine and fatty acid uptake, as well as decreased fatty acid oxidation. These stored lipids serve to protect cancer cells from oxidative and endoplasmic reticulum stress, and play important roles in fueling cancer cell proliferation following re-oxygenation. Lastly, cellular lipids have also been implicated in extracellular vesicle biogenesis, which play a vital role in intercellular communication. Overall, the new understanding of lipid metabolism in recent years has offered several novel targets to better target and manage clinical PCa.

NUPR1, a new target in liver cancer: implication in controlling cell growth, migration, invasion and sorafenib resistance

Sorafenib, an oral multikinase inhibitor, is the only approved agent for the treatment of advanced hepatocellular carcinoma (HCC). However, its benefits are modest, and as its mechanisms of action remain elusive, a better understanding of its anticancer effects is needed. Based on our previous study results, we investigated here the implication of the nuclear protein 1 (NUPR1) in HCC and its role in sorafenib treatment. NUPR1 is a stress-inducible protein that is overexpressed in various malignancies, but its role in HCC is not yet fully understood. We found that NUPR1 expression was significantly higher in primary human HCC samples than in the normal liver. Knockdown of NUPR1 significantly increased cell sensitivity to sorafenib and inhibited the cell growth, migration and invasion of HCC cells, both in vitro and in vivo. Moreover, NUPR1 silencing influenced the expression of RELB and IER3 genes. Unsurprisingly, RELB and IER3 knockdown also inhibited HCC cell viability, growth and migration. Using gene expression profiling of HCC cells following stable NUPR1 knockdown, we found that genes functionally involved in cell death and survival, cellular response to therapies, lipid metabolism, cell growth and proliferation, molecular transport and cellular movement were mostly suppressed. Network analysis of dynamic gene expression identified NF-κB and ERK as downregulated gene nodes, and several HCC-related oncogenes were also suppressed. We identified Runt-related transcription factor 2 (RUNX2) gene as a NUPR1-regulated gene and demonstrated that RUNX2 gene silencing inhibits HCC cell viability, growth, migration and increased cell sensitivity to sorafenib. We propose that the NUPR1/RELB/IER3/RUNX2 pathway has a pivotal role in hepatocarcinogenesis. The identification of the NUPR1/RELB/IER3/RUNX2 pathway as a potential therapeutic target may contribute to the development of new treatment strategies for HCC management.

Modulation of Autophagy by Sorafenib: Effects on Treatment Response

The multikinase inhibitor sorafenib is, at present, the only drug approved for the treatment of hepatocellular carcinoma (HCC), one of the most lethal types of cancer worldwide. However, the increase in the number of sorafenib tumor resistant cells reduces efficiency. A better knowledge of the intracellular mechanism of the drug leading to reduced cell survival could help to improve the benefits of sorafenib therapy. Autophagy is a bulk cellular degradation process activated in a broad range of stress situations, which allows cells to degrade misfolded proteins or dysfunctional organelles. This cellular route can induce survival or death, depending on cell status and media signals. Sorafenib, alone or in combination with other drugs is able to induce autophagy, but cell response to the drug depends on the complex integrative crosstalk of different intracellular signals. In cancerous cells, autophagy can be regulated by different cellular pathways (Akt-related mammalian target of rapamycin (mTOR) inhibition, 5′ AMP-activated protein kinase (AMPK) induction, dissociation of B-cell lymphoma 2 (Bcl-2) family proteins from Beclin-1), or effects of some miRNAs. Inhibition of mTOR signaling by sorafenib and diminished interaction between Beclin-1 and myeloid cell leukemia 1 (Mcl-1) have been related to induction of autophagy in HCC. Furthermore, changes in some miRNAs, such as miR-30α, are able to modulate autophagy and modify sensitivity in sorafenib-resistant cells. However, although AMPK phosphorylation by sorafenib seems to play a role in the antiproliferative action of the drug, it does not relate with modulation of autophagy. In this review, we present an updated overview of the effects of sorafenib on autophagy and its related activation pathways, analyzing in detail the involvement of autophagy on sorafenib sensitivity and resistance.

NGF-induced TrkA/CD44 association is involved in tumor aggressiveness and resistance to lestaurtinib

There is accumulating evidence that TrkA and its ligand Nerve Growth Factor (NGF) are involved in cancer development. Staurosporine derivatives such as K252a and lestaurtinib have been developed to block TrkA kinase signaling, but no clinical trial has fully demonstrated their therapeutic efficacy. Therapeutic failures are likely due to the existence of intrinsic signaling pathways in cancer cells that impede or bypass the effects of TrkA tyrosine kinase inhibitors. To verify this hypothesis, we combined different approaches including mass spectrometry proteomics, co-immunoprecipitation and proximity ligation assays. We found that NGF treatment induced CD44 binding to TrkA at the plasma membrane and subsequent activation of the p115RhoGEF/RhoA/ROCK1 pathway to stimulate breast cancer cell invasion. The NGF-induced CD44 signaling was independent of TrkA kinase activity. Moreover, both TrkA tyrosine kinase inhibition with lestaurtinib and CD44 silencing with siRNA inhibited cell growth in vitro as well as tumor development in mouse xenograft model; combined treatment significantly enhanced the antineoplastic effects of either treatment alone. Altogether, our results demonstrate that NGF-induced tyrosine kinase independent TrkA signaling through CD44 was sufficient to maintain tumor aggressiveness. Our findings provide an alternative mechanism of cancer resistance to lestaurtinib and indicate that dual inhibition of CD44 and TrkA tyrosine kinase activity may represent a novel therapeutic strategy.

Bufalin Reverses Resistance to Sorafenib by Inhibiting Akt Activation in Hepatocellular Carcinoma: The Role of Endoplasmic Reticulum Stress

Sorafenib is the standard first-line therapeutic treatment for patients with advanced hepatocellular carcinoma (HCC), but its use is hampered by the development of drug resistance. The activation of Akt by sorafenib is thought to be responsible for this resistance. Bufalin is the major active ingredient of the traditional Chinese medicine Chan su, which inhibits Akt activation; therefore, Chan su is currently used in the clinic to treat cancer. The present study aimed to investigate the ability of bufalin to reverse both inherent and acquired resistance to sorafenib. Bufalin synergized with sorafenib to inhibit tumor cell proliferation and induce apoptosis. This effect was at least partially due to the ability of bufalin to inhibit Akt activation by sorafenib. Moreover, the ability of bufalin to inactivate Akt depended on endoplasmic reticulum (ER) stress mediated by inositol-requiring enzyme 1 (IRE1). Silencing IRE1 with siRNA blocked the bufalin-induced Akt inactivation, but silencing eukaryotic initiation factor 2 (eIF2) or C/EBP-homologous protein (CHOP) did not have the same effect. Additionally, silencing Akt did not influence IRE1, CHOP or phosphorylated eIF2α expression. Two sorafenib-resistant HCC cell lines, which were established from human HCC HepG2 and Huh7 cells, were refractory to sorafenib-induced growth inhibition but were sensitive to bufalin. Thus, Bufalin reversed acquired resistance to sorafenib by downregulating phosphorylated Akt in an ER-stress-dependent manner via the IRE1 pathway. These findings warrant further studies to examine the utility of bufalin alone or in combination with sorafenib as a first- or second-line treatment after sorafenib failure for advanced HCC.

ATF4 Gene Network Mediates Cellular Response to the Anticancer PAD Inhibitor YW3-56 in Triple-Negative Breast Cancer Cells

We previously reported that a pan-PAD inhibitor, YW3-56, activates p53 target genes to inhibit cancer growth. However, the p53-independent anticancer activity and molecular mechanisms of YW3-56 remain largely elusive. Here, gene expression analyses found that ATF4 target genes involved in endoplasmic reticulum (ER) stress response were activated by YW3-56. Depletion of ATF4 greatly attenuated YW3-56-mediated activation of the mTORC1 regulatory genes SESN2 and DDIT4. Using the ChIP-exo method, high-resolution genomic binding sites of ATF4 and CEBPB responsive to YW3-56 treatment were generated. In human breast cancer cells, YW3-56-mediated cell death features mitochondria depletion and autophagy perturbation. Moreover, YW3-56 treatment effectively inhibits the growth of triple-negative breast cancer xenograft tumors in nude mice. Taken together, we unveiled the anticancer mechanisms and therapeutic potentials of the pan-PAD inhibitor YW3-56.

Induction of endoplasmic reticulum stress as a strategy for melanoma therapy: is there a future?

Melanoma cells employ several survival strategies, including induction of the unfolded protein response, which mediates resistance to endoplasmic reticulum (ER) stress-induced apoptosis. Activation of oncogenes specifically suppresses ER stress-induced apoptosis, while upregulation of ER chaperone proteins and antiapoptotic BCL-2 family members increases the protein folding capacity of the cell and the threshold for the induction of ER stress-induced apoptosis, respectively. Modulation of unfolded protein response signaling, inhibition of the protein folding machinery and/or active induction of ER stress may thus represent potential strategies for the therapeutic management of melanoma. To this aim, the present article focuses on the current understanding of how melanoma cells avoid or overcome ER stress-induced apoptosis, as well as therapeutic strategies through which to harness ER stress for therapeutic benefit.