ERK/BCL-2 pathway in the resistance of pancreatic cancer to anoikis

Comprehensive review of Bcl-2 family proteins in cancer apoptosis: Therapeutic strategies and promising updates of natural bioactive compounds and small molecules

Cancer has a considerably higher fatality rate than other diseases globally and is one of the most lethal and profoundly disruptive ailments. The increasing incidence of cancer among humans is one of the greatest challenges in the field of healthcare. A significant factor in the initiation and progression of tumorigenesis is the dysregulation of physiological processes governing cell death, which results in the survival of cancerous cells. B-cell lymphoma 2 (Bcl-2) family members play important roles in several cancer-related processes. Drug research and development have identified various promising natural compounds that demonstrate potent anticancer effects by specifically targeting Bcl-2 family proteins and their associated signaling pathways. This comprehensive review highlights the substantial roles of Bcl-2 family proteins in regulating apoptosis, including the intricate signaling pathways governing the activity of these proteins, the impact of reactive oxygen species, and the crucial involvement of proteasome degradation and the stress response. Furthermore, this review discusses advances in the exploration and potential therapeutic applications of natural compounds and small molecules targeting Bcl-2 family proteins and thus provides substantial scientific information and therapeutic strategies for cancer management.

Host-derived growth factors drive ERK phosphorylation and MCL1 expression to promote osteosarcoma cell survival during metastatic lung colonization

PURPOSE

For patients with osteosarcoma, disease-related mortality most often results from lung metastasis-a phenomenon shared with many solid tumors. While established metastatic lesions behave aggressively, very few of the tumor cells that reach the lung will survive. By identifying mechanisms that facilitate survival of disseminated tumor cells, we can develop therapeutic strategies that prevent and treat metastasis.

METHODS

We analyzed single cell RNA-sequencing (scRNAseq) data from murine metastasis-bearing lungs to interrogate changes in both host and tumor cells during colonization. We used these data to elucidate pathways that become activated in cells that survive dissemination and identify candidate host-derived signals that drive activation. We validated these findings through live cell reporter systems, immunocytochemistry, and fluorescent immunohistochemistry. We then validated the functional relevance of key candidates using pharmacologic inhibition in models of metastatic osteosarcoma.

RESULTS

Expression patterns suggest that the MAPK pathway is significantly elevated in early and established metastases. MAPK activity correlates with expression of anti-apoptotic genes, especially MCL1. Niche cells produce growth factors that increase ERK phosphorylation and MCL1 expression in tumor cells. Both early and established metastases are vulnerable to MCL1 inhibition, but not MEK inhibition in vivo. Combining MCL1 inhibition with chemotherapy both prevented colonization and eliminated established metastases in murine models of osteosarcoma.

CONCLUSION

Niche-derived growth factors drive MAPK activity and MCL1 expression in osteosarcoma, promoting metastatic colonization. Although later metastases produce less MCL1, they remain dependent on it. MCL1 is a promising target for clinical trials in both human and canine patients.

Isoliensinine augments the therapeutic potential of paclitaxel in multidrug-resistant colon cancer stem cells and induced mitochondria-mediated cell death

Previously we have reported the isoliensinine (ISO) potentates the therapeutic potential of cisplatin in cisplatin resistant colorectal cancer stem cells. The present study evaluates the chemo-sensitizing potential of the combinatorial regimen of ISO and Paclitaxcel (PTX) on multidrug-resistant (MDR)-HCT-15 cells to reduce the dose requirement of both ISO and PTX. The results of the present study suggest that treatment with the combinatorial regimen of ISO and PTX enhanced the cytotoxic effect with resultant increase in apoptosis in MDR-HCT-15 cells as evident from the altered cellular morphology, G2/M cell cycle arrest, propidium iodide uptake, Annexin V, increased intracellular Ca2+ accumulation, decreased mitochondrial membrane potential, diminished ATP production, PARP-1 cleavage, altered expression of ERK1/2, and apoptotic proteins. Treatment with combinatorial regimen of ISO and PTX also modulated the expression of the transcription factors SOX2, OCT4 which determine the stemness of cancer cells. Thus, results of the present study suggest that ISO and PTX combination regimen induces apoptosis in MDR-HCT-15 in a synergistic manner.

Identification and characterization of a first-generation inhibitor of claudin-1 in colon cancer progression and metastasis

Colorectal cancer (CRC) is a leading cause of the cancer-related deaths worldwide. Thus, developing novel and targeted therapies for inhibiting CRC progression and metastasis is urgent. Several studies, including ours, have reported a causal role for an upregulated claudin-1 expression in promoting CRC metastasis through the activation of the Src and β-catenin-signaling. In murine models of colon tumorigenesis, claudin-1 overexpression promotes oncogenic properties such as transformation and invasiveness. Conversely, the downregulation of claudin-1 inhibits colon tumorigenesis. Despite being a desirable target for cancer treatment, there are currently no known claudin-1 inhibitors with antitumor efficacy. Using a rigorous analytical design and implementing in- vitro and in-vivo testing and a brief medicinal chemistry campaign, we identified a claudin-1-specific inhibitor and named it I-6. Despite its high potency, I-6 was rapidly cleared in human liver microsomes. We, therefore, synthesized I-6 analogs and discovered a novel small molecule, PDS-0330. We determined that PDS0330 inhibits claudin-1-dependent CRC progression without exhibiting toxicity in in-vitro and in-vivo models of CRC and that it binds directly and specifically to claudin-1 with micromolar affinity. Further analyses revealed that PDS-0330 exhibits antitumor and chemosensitizer activities with favorable pharmacokinetic properties by inhibiting the association with metastatic oncogene Src. Overall, our data propose that PDS-0330 interferes with claudin-1/Src association to inhibit CRC progression and metastasis. Our findings are of direct clinical relevance and may open new therapeutic opportunities in colon cancer treatment and/or management by targeting claudin-1.

GSNOR deficiency promotes tumor growth via FAK1 S-nitrosylation

Nitric oxide (NO) production in the tumor microenvironment is a common element in cancer. S-nitrosylation, the post-translational modification of cysteines by NO, is emerging as a key transduction mechanism sustaining tumorigenesis. However, most oncoproteins that are regulated by S-nitrosylation are still unknown. Here we show that S-nitrosoglutathione reductase (GSNOR), the enzyme that deactivates S-nitrosylation, is hypo-expressed in several human malignancies. Using multiple tumor models, we demonstrate that GSNOR deficiency induces S-nitrosylation of focal adhesion kinase 1 (FAK1) at C658. This event enhances FAK1 autophosphorylation and sustains tumorigenicity by providing cancer cells with the ability to survive in suspension (evade anoikis). In line with these results, GSNOR-deficient tumor models are highly susceptible to treatment with FAK1 inhibitors. Altogether, our findings advance our understanding of the oncogenic role of S-nitrosylation, define GSNOR as a tumor suppressor, and point to GSNOR hypo-expression as a therapeutically exploitable vulnerability in cancer.

Expression of plant-produced anti-PD-L1 antibody with anoikis sensitizing activity in human lung cancer cells via., suppression on epithelial-mesenchymal transition

Immune checkpoint antibodies in cancer treatment are receptor-ligand pairs that modulate cancer immunity. PD-1/PD-L1 pathway has emerged as one of the major targets in cancer immunotherapy. Atezolizumab, the first anti-PD-L1 antibody approved for the treatment of metastatic urothelial, non-small cell lung, small cell lung and triple-negative breast cancers, is produced in Chinese Hamster Ovary (CHO) cells with several limitations i.e., high-production costs, low-capacity yields, and contamination risks. Due to the rapid scalability and low production costs, the transient expression in Nicotiana benthamiana leaves was investigated by co-infiltration of Agrobacterium tumefaciens GV3101 cultures harboring the nucleic acid sequences encoding for Atezolizumab heavy chain and light chain in this study. The transient expression of Atezolizumab in transformed N. benthamiana accumulated up to 86.76 μg/g fresh leaf weight after 6 days of agroinfiltration (OD 600 nm: 0.4) with 1:1 ratio of heavy chain to light chain. The structural and functional characteristics of plant-produced Atezolizumab was compared with commercially available Tecentriq^® from CHO cells with similar binding efficacies to PD-L1 receptor. The direct anti-cancer effect of plant-produced anti-PD-L1 was further performed in human lung metastatic cancer cells H460 cultured under detachment condition, demonstrating the activity of anti-PD-L1-antibody on sensitizing anoikis as well as the suppression on anti-apoptosis proteins (Bcl-2 and Mcl-1) and modulation of epithelial to mesenchymal regulating proteins (E-cadherin, N-cadherin, Snail and Slug). In conclusion, this study manifests plants as an alternative cost-effective platform for the production of functional monoclonal antibodies for use in cancer therapy.

Understanding the cell survival mechanism of anoikis-resistant cancer cells during different steps of metastasis

Anchorage-independent survival of cancer cells is associated with metastasis as it enables cells to travel to secondary target sites. Tissue integrity is generally maintained by detachment-induced cell death called 'anoikis', but cancer cells undergoing the multistep metastatic process show resistance to anoikis. Anoikis resistance enables these cells to survive through the extracellular matrix (ECM) deprived phase, which starts when cancer cells detach and move into the circulation till cells reach to the secondary target site. Comprehensive analysis of the molecular and functional biology of anoikis resistance in cancer cells will provide crucial details about cancer metastasis, enabling us to identify novel therapeutic targets against cancer cell dissemination and ultimately secondary tumor formation. This review broadly summarizes recent advances in the understanding of cellular and molecular events leading to anoikis and anoikis resistance. It further elaborates more about the signaling cross-talk in anoikis resistance and its regulation during metastasis.

Exploration of the System-Level Mechanisms of the Herbal Drug FDY003 for Pancreatic Cancer Treatment: A Network Pharmacological Investigation

Pancreatic cancer (PC) is the most lethal cancer with the lowest survival rate globally. Although the prescription of herbal drugs against PC is gaining increasing attention, their polypharmacological therapeutic mechanisms are yet to be fully understood. Based on network pharmacology, we explored the anti-PC properties and system-level mechanisms of the herbal drug FDY003. FDY003 decreased the viability of human PC cells and strengthened their chemosensitivity. Network pharmacological analysis of FDY003 indicated the presence of 16 active phytochemical components and 123 PC-related pharmacological targets. Functional enrichment analysis revealed that the PC-related targets of FDY003 participate in the regulation of cell growth and proliferation, cell cycle process, cell survival, and cell death. In addition, FDY003 was shown to target diverse key pathways associated with PC pathophysiology, namely, the PIK3-Akt, MAPK, FoxO, focal adhesion, TNF, p53, HIF-1, and Ras pathways. Our network pharmacological findings advance the mechanistic understanding of the anti-PC properties of FDY003 from a system perspective.

Spred1 deficit promotes treatment resistance and transformation of chronic phase CML

Spred1 is highly expressed in normal hematopoietic stem cells (HSCs). Lack of Spred1 function has been associated with aberrant hematopoiesis and acute leukemias. In chronic myelogenous leukemia (CML), Spred1 is reduced in patients with accelerated phase (AP) or blast crisis (BC) CML, thereby suggesting that deficit of this protein may contribute to disease transformation. In fact, Spred1 knockout (KO) in SCLtTA/BCR-ABL CML mice either globally, or restricted to hematopoietic cells (i.e., HSCs) or to endothelial cells (ECs), led to transformation of chronic phase (CP) CML into AP/BC CML. Upon BCR-ABL induction, all three Spred1 KO CML models showed AP/BC features. However, compared with global Spred1 KO, the AP/BC phenotypes of HSC-Spred1 KO and EC-Spred1 KO CML models were attenuated, suggesting a concurrent contribution of Spred1 deficit in multiple compartments of the leukemic bone marrow niche to the CML transformation. Spred1 KO, regardless if occurred in HSCs or in ECs, increased miR-126 in LSKs (Lin-Sca-1+c-Kit+), a population enriched in leukemic stem cells (LSCs), resulting in expansion of LSCs, likely through hyperactivation of the MAPK/ERK pathway that augmented Bcl-2 expression and stability. This ultimately led to enhancement of Bcl-2-dependent oxidative phosphorylation that supported homeostasis, survival and activity of LSCs and drove AP/BC transformation.

Targeted silencing of TEM8 suppresses non‑small cell lung cancer tumor growth via the ERK/Bcl‑2 signaling pathway

Non-small cell lung cancer (NSCLC) is one of the most common malignancies with high rates of mortality. Although great progress has been made with the development of novel immunotherapies and targeted therapeutic strategies, the 5-year total survival rate of lung cancer has remained unchanged over the past few decades. Therefore, more effective therapeutics are urgently needed. Tumor endothelial marker 8 (TEM8) is an integrin-like cell surface transmembrane protein that has been demonstrated to be upregulated in numerous cancer types and previously showed promise for targeted cancer therapy. However, the role of TEM8 in NSCLC remains poorly understood. The present study aimed to investigate the effects of silencing TEM8 on expression and regulation of extracellular signal-regulated kinase (ERK)1/2 signaling pathways in NSCLC. In the present study, a lentiviral vector that encoded a short hairpin RNA targeting TEM8 was designed and transfected into Xuanwei Lung Cancer (XWLC)-05 lung cancer cells to silence TEM8 expression. Male BALB/c-nu/nu mice were then given subcutaneous injections in the right dorsal flank with XWLC-05 cells. Microvessel density was measured using an anti-CD34 antibody. The mRNA and protein levels of ERK1/2 and Bcl-2 in XWLC-05 cells or xenograft tumor tissues were detected by reverse transcription-quantitative polymerase chain reaction and western blotting. TEM8 knockdown was found to significantly inhibit tumor growth and conferred an anti-angiogenic ability in vivo. Furthermore, TEM8 knockdown suppressed the expression of Bcl-2 mediated by ERK1/2 activity in XWLC-05 cells or tissues from mice with NSCLC. To conclude, these results suggest that the targeted silencing of TEM8 may serve as an effective method of treating NSCLC.

Angiopoietin-like protein 2 decreases peritoneal metastasis of ovarian cancer cells by suppressing anoikis resistance

Peritoneal metastasis is a common mode of spread of ovarian cancer. Despite therapeutic advances, some patients have intractable peritoneal metastasis. Therefore, in-depth characterization of the molecular mechanism of peritoneal metastasis is a key imperative. Angiopoietin-like protein 2 (ANGPTL2) is an inflammatory factor which activates NF-κB signaling and plays an important role in the pathogenesis of various inflammatory diseases including cancers, such as lung and breast cancer. In this study, we examined the role of ANGPTL2 in ovarian cancer peritoneal metastasis. We observed no difference of cell proliferation between ANGPTL2-expressing and control cells. In the mouse intraperitoneal xenograft model, formation of peritoneal metastasis by ANGPTL2-expressing cells was significantly decreased compared to control. In the in vitro analysis, the expressions of integrin α5β1, α6, and β4, but not those of αvβ3, α3, α4, and β1, were significantly decreased in ANGPTL2-expressing cells compared to control cells. ANGPTL2-expressing cells showed significantly inhibited adherence to laminin compared to control. In addition, we observed upregulation of anoikis (a form of programmed cell death occurring under an anchorage-independent condition) and significant decrease in the expression of Bcl-2 in ANGPTL2-expressing cells as compared to control cells. These results suggest that ANGPTL2 expression in ovarian cancer cells represses peritoneal metastasis by suppressing anoikis resistance.

Dual Effects of Non-Coding RNAs (ncRNAs) in Cancer Stem Cell Biology

The identification of cancer stem cells (CSCs) as initiators of carcinogenesis has revolutionized the era of cancer research and our perception for the disease treatment options. Additional CSC features, including self-renewal and migratory and invasive capabilities, have further justified these cells as putative diagnostic, prognostic, and therapeutic targets. Given the CSC plasticity, the identification of CSC-related biomarkers has been a serious burden in CSC characterization and therapeutic targeting. Over the past decades, a compelling amount of evidence has demonstrated critical regulatory functions of non-coding RNAs (ncRNAs) on the exclusive features of CSCs. We now know that ncRNAs may interfere with signaling pathways, vital for CSC phenotype maintenance, such as Notch, Wnt, and Hedgehog. Here, we discuss the multifaceted contribution of microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), as representative ncRNA classes, in sustaining the CSC-like traits, as well as the underlying molecular mechanisms of their action in various CSC types. We further discuss the use of CSC-related ncRNAs as putative biomarkers of high diagnostic, prognostic, and therapeutic value.

Integrin-EGFR interaction regulates anoikis resistance in colon cancer cells

Anoikis resistance is an essential property of cancer cells that allow the extra-cellular matrix-detached cells to survive in a suspended state in body fluid in order to metastasize and invade to distant organs. It is known that integrins play an important role in anoikis resistance, but detailed mechanisms are not well understood. Here we report that highly metastatic colon cancer cells showed a higher degree of anoikis resistance than the normal intestinal epithelial cells. These anoikis-resistant cancer cells express high-levels of integrin-α2, β1, and activated EGFR in the anchorage-independent state than the anchorage-dependent state. In contrast, normal intestinal epithelial cells failed to elevate these proteins. Interestingly, a higher co-association of EGFR with integrin-α2β1/-α5β1 was observed on the surface of anoikis-resistant cells. Thus, in the absence of extra-cellular matrix, integrins in association with EGFR activates downstream effectors ERK and AKT and suppress Caspase-3 activation to induce anoikis resistance as was confirmed from the gene-ablation and pharmacological inhibitor studies. Interestingly, these anoikis-resistant cancer cells express high-level of cancer stem cell signatures (CD24, CD44, CD133, EpCAM) and pluripotent stem cell markers (OCT-4, SOX-2, Nanog) as well as drug-resistant pumps (ABCG2, MDR1, MRP1). Altogether, our findings unravel the interplay between integrin-α2β1/-α5β1 and EGFR in anoikis resistance and suggest that the resistant cells are cancer initiating or cancer stem cells, which may serve as a promising target to combat metastasis of cancer.

Functional Significance and Therapeutic Potential of miR-15a Mimic in Pancreatic Ductal Adenocarcinoma

Treatment of pancreatic ductal adenocarcinoma (PDAC) remains a clinical challenge. There is an urgent need to develop novel strategies to enhance survival and improve patient prognosis. MicroRNAs (miRNAs) play critical roles as oncogenes or tumor suppressors in the regulation of cancer development and progression. In this study, we demonstrate that low expression of miR-15a is associated with poor prognosis of PDAC patients. miR-15a expression is reduced in PDAC while closely related miR-16 expression remains relatively unchanged. miR-15a suppresses several important targets such as Wee1, Chk1, Yap-1, and BMI-1, causing cell cycle arrest and inhibiting cell proliferation. Ectopic expression of miR-15a sensitizes PDAC cells to gemcitabine reducing the half maximal inhibitory concentration (IC₅₀) more than 6.5-fold. To investigate the therapeutic potential of miR-15a, we used a modified miR-15a (5-FU-miR-15a) with uracil (U) residues in the guide strand replaced with 5-fluorouracil (5-FU). We demonstrated enhanced inhibition of PDAC cell proliferation by 5-FU-miR-15a compared to native miR-15a. In vivo we showed the therapeutic power of 5-FU-miR-15a alone or in combination with gemcitabine with near complete elimination of PDAC lung metastatic tumor growth. These results support the future development of 5-FU-miR-15a as a novel therapeutic agent as well as a prognostic biomarker in the clinical management of PDAC.

High Expression of Plakoglobin Promotes Metastasis in Invasive Micropapillary Carcinoma of the Breast via Tumor Cluster Formation

Invasive micropapillary carcinoma of the breast (IMPC) is a rare subtype of breast cancer that has a high frequency of lymph node (LN) involvement and metastasis to distant organs. IMPC is characterized by distinct histomorphology and unfavorable prognosis when compared with invasive ductal carcinoma no special type (IDC-NST). However, the underlying molecular mechanisms remain unclear. We reported here that plakoglobin, as a key component in cell adhesion, can promote collective metastasis through facilitating IMPC clusters formation. In comparing the clinicopathological features of 451 IMPC patients and 282 IDC-NST patients, our results showed that tumor emboli were significantly higher in IMPC patients and were associated with a high frequency of metastasis. Both in vitro and in vivo data showed overexpression of plakoglobin in both the cell membrane and the cytoplasm of IMPC clusters. When plakoglobin was knocked down in IMPC cell models, the tumor cell clusters were depolymerized. Using mouse models, we validated the metastatic potential of tumor clusters was higher than single cells in vivo. Further analysis showed that higher expression of plakoglobin was able to promote activation of the PI3K/Akt/Bcl-2 pathway, which might protect the clusters from anoikis. Our data indicate that plakoglobin promotes tumor cluster formation in IMPC and downregulates apoptosis in the cell clusters through activation of PI3K/Akt/Bcl-2 signaling. These results provide a convincing rationale for the high metastatic propensity seen in IMPC.

Metastasis inhibition in breast cancer by targeting cancer cell extravasation

The spread of cells from primary tumors toward distant tissues and organs, also known as metastasis, is responsible for most cancer-associated deaths. The metastasis cascade comprises a series of events, characterized by the displacement of tumor cells (TCs) from the primary tumor to distant organs by traveling through the bloodstream, and their subsequent colonization. The first step in metastasis involves loss of cell-cell and cell-matrix adhesions, increased invasiveness and migratory abilities, leading to intravasation of TCs into the blood or lymphatic vessels. Stationary TCs must undergo the process of epithelial-mesenchymal transition in order to achieve this migratory and invasive phenotype. Circulating tumor cells that have survived in the circulation and left the blood or lymphatic vessels will reach distant sites where they may stay dormant for many years or grow to form secondary tumors. To do this, cells need to go through the mesenchymal-epithelial transition to revert the phenotype in order to regain epithelial cell-to-cell junctions, grow and become a clinically relevant and detectable tumor mass. This work will review the main steps of the metastatic cascade and describe some strategies to inhibit metastasis by reducing cancer cell extravasation presenting recent studies in the context of breast cancer.

Antitumor Efficacy of Huqizhengxiao (HQZX) Decoction Based on Inhibition of Telomerase Activity in Nude Mice of Hepatocarcinoma Xenograft

Objective: Huqizhengxiao (HQZX) decoction is a mixture of traditional Chinese medicines comprising 10 herbs, with inhibitory effects on hepatocarcinoma. The aim of the study is to observe the antitumor efficacy and mechanism of HQZX decoction in nude mice with hepatocellular carcinoma xenografts. Methods: HepG2-luc subcutaneous hepatocarcinoma was established in nude mice. The mice were divided into 5 groups: control, cinobufagin, HQZXS, HQZXM, and HQZXH with doses 13.52, 27.03, and 54.06 g/kg, respectively. HQZX decoction was prepared for intraperitoneal intragastric administration for 3 weeks. Tumor growth was measured with Vernier calipers and in vivo imaging system. α-Fetoprotein (AFP) was determined by radioimmunoassay. Tumor necrosis factor–α (TNF-α) was measured with enzyme-linked immunosorbent assay (ELISA) assay. Telomerase activity was measured with polymerase chain reaction–ELISA. Nuclear mitosis and necrosis were observed with hematoxylin-eosin stain. Apoptotic proteins of caspase-3, Bcl-2, and Bax were examined by Western blot. Signaling molecules of ERK, mTOR, and STAT3 were measured with Luminex assay. Results: HQZX decoction showed good inhibition of HepG2-luc xenografts. Compared with control group, the relative tumor proliferation rate was less than 60% in the HQZXH and HQZXS. The tumor inhibition rate of HQZXH group reached 52% ± 15%. Relative average optical density values of the HQZXS and HQZXH groups decreased significantly. The mitotic index in HQZXS, HQZXM, and HQZXH groups decreased greatly. Telomerase activity of HQZXS was clearly reduced, and, the caspase-3 expression upregulated in HQZXH group. Bcl-2 expression was downregulated in HQZXS and HQZXH. The ratios of p-ERK/ERK and p-STAT3/STAT3 in HQZXS group were significantly downregulated. Conclusion: HQZX decoction can clearly inhibit the growth of hepatocellular carcinoma and induce tumor apoptosis. Its antitumor mechanism may be related to reducing telomerase activity and regulating the STAT3 and ERK signal pathway.

Bone marrow niche trafficking of miR-126 controls the self-renewal of leukemia stem cells in chronic myelogenous leukemia

Leukemia stem cells (LSCs) in individuals with chronic myelogenous leukemia (CML) (hereafter referred to as CML LSCs) are responsible for initiating and maintaining clonal hematopoiesis. These cells persist in the bone marrow (BM) despite effective inhibition of BCR-ABL kinase activity by tyrosine kinase inhibitors (TKIs). Here we show that although the microRNA (miRNA) miR-126 supported the quiescence, self-renewal and engraftment capacity of CML LSCs, miR-126 levels were lower in CML LSCs than in long-term hematopoietic stem cells (LT-HSCs) from healthy individuals. Downregulation of miR-126 levels in CML LSCs was due to phosphorylation of Sprouty-related EVH1-domain-containing 1 (SPRED1) by BCR-ABL, which led to inhibition of the RAN-exportin-5-RCC1 complex that mediates miRNA maturation. Endothelial cells (ECs) in the BM supply miR-126 to CML LSCs to support quiescence and leukemia growth, as shown using mouse models of CML in which Mir126a (encoding miR-126) was conditionally knocked out in ECs and/or LSCs. Inhibition of BCR-ABL by TKI treatment caused an undesired increase in endogenous miR-126 levels, which enhanced LSC quiescence and persistence. Mir126a knockout in LSCs and/or ECs, or treatment with a miR-126 inhibitor that targets miR-126 expression in both LSCs and ECs, enhanced the in vivo anti-leukemic effects of TKI treatment and strongly diminished LSC leukemia-initiating capacity, providing a new strategy for the elimination of LSCs in individuals with CML.

MEK inhibitor, PD98059, promotes breast cancer cell migration by inducing β-catenin nuclear accumulation

Abnormal activation of the RAF/MEK/ERK signaling pathway has been observed in breast cancer. Thus, a number of MEK inhibitors have been designed as one treatment option for breast cancer. Although some studies have found that these MEK inhibitors inhibit the growth of a variety of human cancer cells, some trials have shown that the use of MEK inhibitors as a treatment for breast cancer does not adequately improve survival for unknown reasons. In the present study, MEK inhibitor PD98059 was used to evaluate its anticancer effects on human breast cancer MCF-7 and MDA-MB-231 cells and to explore the possible mechanism of action. Our results revealed that MEK inhibitor PD98059 exhibited antiproliferative effects in a dose- and time-dependent manner in MCF-7 and MDA-MB-231 breast cancer cells. Conversely, incubation of MCF-7 and MDA-MB-231 cells with PD98059 promoted their migration. Further investigation disclosed that the enhanced ability of migration promoted by PD98059 was dependent on β-catenin nuclear translocation in the MCF-7 and MDA-MB‑231 cells. Subsequent experiments documented that activation of EGFR signaling induced by PD98059 increased the amount of β-catenin in the nucleus. Taken together, our findings may elucidate a possible mechanism explaining the ineffectiveness of MEK inhibitors in breast cancer treatment and improve our understanding of the role of MEK in cancer.

Expression and functions of the STAT3-SCLIP pathway in chronic myeloid leukemia cells

Chronic myeloid leukemia (CML) is a blood cell cancer with increased proliferation of granulocytes. Signal transducers and activators of transcription 3 (STAT3) is an important regulator of CML. To investigate the possible downstream factors of STAT3 and gain more insight into CML-related pathways, this study focused on the superior cervical ganglia protein 10-like protein (SCLIP, or SCG 10-like protein) and analyzed the functions of the STAT3-SCLIP pathway. The effects of STAT3 phosphorylation on SCLIP expression were examined by western blotting. Specific small interfering RNA (siRNA) was then used to knockdown SCLIP in the CML cell line K562 and the expression changes of STAT3 and factors further downstream, namely Bcl-2 and cyclin E1, were detected by RT-qPCR. Cell viability and apoptosis were also analyzed following the knockdown of SCLIP. Results showed a positive association between the phosphorylation of STAT3 and the expression of SCLIP. Knockdown of SCLIP inhibited the viability and induced the apoptosis of K562 cells. Knockdown of SCLIP did not affect the expression of STAT3 mRNA but downregulated the mRNA levels of Bcl-2 and cyclin E1. In conclusion, the results indicate that SCLIP is a direct downstream factor of STAT3, regulates Bcl-2 and cyclin E1 and mediates the viability and apoptosis of CML cells. Consisting of at least these four factors, the STAT3-SCLIP pathway might play critical roles in the regulation of CML. These data provided a more profound understanding of CML-related pathways.

MiR-449a regulates autophagy to inhibit silica-induced pulmonary fibrosis through targeting Bcl2

Silicosis is a fatal pulmonary fibrotic disorder characterized by accumulation of fibroblasts and myofibroblasts and deposition of extracellular matrix proteins. MiR-449a is a potential mediator of many cellular processes, including cell proliferation, differentiation, and apoptosis. We hypothesized that miR-449a may play a crucial role in the progression of pulmonary fibrogenesis. Here, we described miR-449a as a new autophagy-regulated miRNA. Importantly, miR-449a expression was significantly decreased in lung tissues of mice with silica treatment, and it was similarly expressed in NIH-3T3 and MRC-5 cells stimulated with TGF-β1. The activity of autophagy was inhibited in fibrotic lung tissues and TGF-β1-treated fibroblasts. To investigate the potential effect of miR-449a, we overexpressed miR-449a in mouse models and found that miR-449a significantly reduced both the distribution and severity of lung lesions induced by silica. In addition, miR-449a was observed to induce the activity of autophagy in vivo and in vitro. Notably, Bcl2 was identified as a target of miR-449a. Bcl2 levels were decreased in NIH-3T3 cells upon miR-449a overexpression. Indeed, the Bcl2 3' UTR contained functional miR-449a responsive sequences. Furthermore, TGF-β1 was observed to increase the expression of Bcl2 via the MAPK/ERK pathway. These results suggest that miR-449a is an important regulator of autophagy, as well as a novel endogenous suppressor of pulmonary fibrosis.

KEY MESSAGE

MiR-449a expression was decreased in fibrotic lungs and activated fibroblasts. Autophagy was inhibited in fibrotic lung tissues and TGF-β1-treated fibroblasts. MiR-449a had an antifibrotic effect in silica-induced lung fibrosis. MiR-449a upregulated autophagic activity in vitro. Bcl2 is the autophagy-related target of miR-449a.

An Automated High-throughput Array Microscope for Cancer Cell Mechanics

Changes in cellular mechanical properties correlate with the progression of metastatic cancer along the epithelial-to-mesenchymal transition (EMT). Few high-throughput methodologies exist that measure cell compliance, which can be used to understand the impact of genetic alterations or to screen the efficacy of chemotherapeutic agents. We have developed a novel array high-throughput microscope (AHTM) system that combines the convenience of the standard 96-well plate with the ability to image cultured cells and membrane-bound microbeads in twelve independently-focusing channels simultaneously, visiting all wells in eight steps. We use the AHTM and passive bead rheology techniques to determine the relative compliance of human pancreatic ductal epithelial (HPDE) cells, h-TERT transformed HPDE cells (HPNE), and four gain-of-function constructs related to EMT. The AHTM found HPNE, H-ras, Myr-AKT, and Bcl2 transfected cells more compliant relative to controls, consistent with parallel tests using atomic force microscopy and invasion assays, proving the AHTM capable of screening for changes in mechanical phenotype.

Protein Kinase A Activation Promotes Cancer Cell Resistance to Glucose Starvation and Anoikis

Cancer cells often rely on glycolysis to obtain energy and support anabolic growth. Several studies showed that glycolytic cells are susceptible to cell death when subjected to low glucose availability or to lack of glucose. However, some cancer cells, including glycolytic ones, can efficiently acquire higher tolerance to glucose depletion, leading to their survival and aggressiveness. Although increased resistance to glucose starvation has been shown to be a consequence of signaling pathways and compensatory metabolic routes activation, the full repertoire of the underlying molecular alterations remain elusive. Using omics and computational analyses, we found that cyclic adenosine monophosphate-Protein Kinase A (cAMP-PKA) axis activation is fundamental for cancer cell resistance to glucose starvation and anoikis. Notably, here we show that such a PKA-dependent survival is mediated by parallel activation of autophagy and glutamine utilization that in concert concur to attenuate the endoplasmic reticulum (ER) stress and to sustain cell anabolism. Indeed, the inhibition of PKA-mediated autophagy or glutamine metabolism increased the level of cell death, suggesting that the induction of autophagy and metabolic rewiring by PKA is important for cancer cellular survival under glucose starvation. Importantly, both processes actively participate to cancer cell survival mediated by suspension-activated PKA as well. In addition we identify also a PKA/Src mechanism capable to protect cancer cells from anoikis. Our results reveal for the first time the role of the versatile PKA in cancer cells survival under chronic glucose starvation and anoikis and may be a novel potential target for cancer treatment.

Tumor heterogeneity exists in many human cancers, and it has been shown that it can play a role in tumor progression. Indeed, cell diversity may be critically important when tumors experience selective pressures, like nutrient deprivation, hypoxia, chemotherapy. PKA, through incompletely understood mechanisms, controls several cellular processes like cell growth, cell differentiation, cell metabolism, cell migration and, as more recently observed, also cancer progression. In this work, we show that activation of PKA induces the ability of a cancer cell sub-population to survive under strong stress conditions namely nutrient deprivation and cell detachment. Indeed, PKA activation in these cells results in autophagy induction, and at the same time, in activation of glutamine metabolism and Src kinase. Importantly, blocking directly the PKA pathway, as well as the autophagy, the glutamine metabolism or the Src pathway by inhibitory drugs, almost completely prevents cell growth of this sub-population of resistant cancer cells. These results suggest that drugs, targeting especially PKA pathway as well as downstream processes like autophagy, glutamine metabolism and Src signaling, may specifically inhibit cancer cells ability to survive under selective pressure favoring cancer resistance.

CXCL8, overexpressed in colorectal cancer, enhances the resistance of colorectal cancer cells to anoikis

Anoikis is a form of apoptosis which occurs when anchorage-dependent cells either show loss of adhesion or inappropriate adhesion. Only a few cancer cells that detach from the primary site of the tumor acquire the ability to resist anoikis and form metastasis. The mechanism underlying the resistance of colorectal cancer (CRC) cells to anoikis remains unclear. Interleukin-8 (alternatively known as CXCL8) is associated with CRC angiogenesis and progression. Here, we found that a high abundance of CXCL8 or TOPK strongly correlated with poor overall and disease-free survival of 186 patients with CRC. A combination of high CXCL8 and high TOPK expressions had the worst prognosis. We showed that CXCL8 expression was negatively correlated with anoikis in CRC cells. CXCL8 treatment enhanced the resistance of CRC cells to apoptosis, which was accompanied by the increase of TOPK, and the activation of AKT and ERK. Moreover, we demonstrated that the inhibition of either ERK or AKT by specific chemical inhibitors attenuated the CXCL8-mediated resistance to anoikis. Treatment with AKT inhibitor abolished the effects of CXCL8 on TOPK expression, suggesting that TOPK was downstream of AKT in the process of anoikis. Taken together, we demonstrated that CXCL8 is strongly implicated in the resistance of CRC cells to anoikis, and that the AKT, TOPK and ERK pathway may be a potential therapeutic target for CRC.

Resistance to BH3 mimetic S1 in SCLC cells that up-regulate and phosphorylate Bcl-2 through ERK1/2

BACKGROUND AND PURPOSE

B cell lymphoma 2 (Bcl-2) is a central regulator of cell survival that is overexpressed in the majority of small-cell lung cancers (SCLC) and contributes to both malignant transformation and therapeutic resistance. The purpose of this work was to study the key factors that determine the sensitivity of SCLC cells to Bcl-2 homology domain-3 (BH3) mimetic S1 and the mechanism underlying the resistance of BH3 mimetics.

EXPERIMENTAL APPROACHES

Western blot was used to evaluate the contribution of Bcl-2 family members to the cellular response of SCLC cell lines to S1. Acquired resistant cells were derived from initially sensitive H1688 cells. Quantitative PCR and gene silencing were performed to investigate Bcl-2 up-regulation.

KEY RESULTS

A progressive increase in the relative levels of Bcl-2 and phosphorylated Bcl-2 (pBcl-2) characterized the increased de novo and acquired resistance of SCLC cell lines. Furthermore, acute treatment of S1 induced Bcl-2 expression and phosphorylation. We showed that BH3 mimetics, including S1 and ABT-737, induced endoplasmic reticulum (ER) stress and then activated MAPK/ERK pathway. The dual function of MAPK/ERK pathway in defining BH3 mimetics was illustrated; ERK1/2 activation leaded to Bcl-2 transcriptional up-regulation and sustained phosphorylation in naïve and acquired resistant SCLC cells. pBcl-2 played a key role in creating resistance of S1 and ABT-737 not only by sequestrating pro-apoptotic proteins, but also sequestrating a positive feedback to promote ERK1/2 activation.

CONCLUSIONS AND IMPLICATIONS

These results provide significant novel insights into the molecular mechanisms for crosstalk between ER stress and endogenously apoptotic pathways in SCLC following BH3 mimetics treatment.

Involvement of the ERK pathway in the protective effects of glycyrrhizic acid against the MPP+-induced apoptosis of dopaminergic neuronal cells

Glycyrrhizic acid (GA), a major compound separated from Radix Glycyrrhizae, has been shwon to exert various biochemical effects, including neuroprotective effects. In the present study, we investigated the protective effects of GA against 1-methyl-4-phenylpyridinium (MPP+)‑induced damage to differentiated PC12 (DPC12) cells. Compared with the MPP+-treated cells, GA markedly improved cell viability, restored mitochondrial dysfunction, suppressed the overexpression of cleaved poly(ADP-ribose) polymerase (PARP), and suppressed the overproduction of lactate dehydrogenase (LDH) and intracellular Ca2+ overload. The protective effects of GA on cell survival were further confirmed in primary cortical neurons. GA markedly increased the expression of phosphorylated extracellular signal-regulated kinase (p-ERK), as well as its migration from the cytoplasm to nucleus. PD98059, an inhibitor of ERK, blocked GA-enhanced ERK activation and reduced cell viability. However, pre-treatment with GA had no effects on the expression of phosphorylated AKT (p-AKT) and total AKT (t-AKT). These results indicate that the GA-mediated neuroprotective effects are associated with its modulation of multiple anti-apoptotic and pro-apoptotic factors, particularly the ERK signaling pathway. This study provides evidence supporting the use of GA as a potential therapeutic agent for the treatment of neurodegenerative diseases and neuronal injury.

Sigma receptor 1 modulates ER stress and Bcl2 in murine retina

Sigma receptor 1 (σR1), a non-opiate transmembrane protein located on endoplasmic reticulum (ER) and mitochondrial membranes, is considered to be a molecular chaperone. Marked protection against cell death has been observed when ligands for σR1 have been used in in vitro and in vivo models of retinal cell death. Mice lacking σR1 (σR1(-/-)) manifest late-onset loss of retinal ganglion cells and retinal electrophysiological changes (after many months). The role of σR1 in the retina and the mechanisms by which its ligands afford neuroprotection are unclear. We therefore used σR1(-/-) mice to investigate the expression of ER stress genes (BiP/GRP78, Atf6, Atf4, Ire1α) and proteins involved in apoptosis (BCL2, BAX) and to examine the retinal transcriptome at young ages. Whereas no significant changes occurred in the expression of major ER stress genes (over a period of a year) in neural retina, marked changes were observed in these genes, especially Atf6, in isolated retinal Müller glial cells. BCL2 levels decreased in σR1(-/-) retina concomitantly with decreases in NFkB and pERK1/2. We postulate that σR1 regulates ER stress in retinal Müller cells and that the role of σR1 in retinal neuroprotection probably involves BCL2 and some of the proteins that modify its expression (such as ERK, NFκB). Data from the analysis of the retinal transcriptome of σR1 null mice provide new insights into the role of σR1 in retinal neuroprotection.

Activation of ERK1/2 and Akt is associated with cisplatin resistance in human lung cancer cells

Cisplatin is widely used for the treatment of solid tumours including small cell lung cancers, but its success is often compromised by relapse and resistance to further treatment. Extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt are two major cell survival pathways that are upregulated and activated in lung cancer tissues. Phosphorylated ERK1/2 (p-ERK1/2) and Akt (p-Akt) can be further stimulated by chemotherapeutics in cancer cells. Although individually targeting the ERK1/2 or Akt pathway has been reported to sensitize cancer cells to therapy, the effect of concurrently blocking these two pathways on the sensitivity of lung cancer cells to cisplatin has not been investigated. In the present study, we aimed to determine whether the ERK1/2 and Akt pathways contribute to cisplatin resistance in human small cell lung cancer A549 cells. The results showed that cisplatin activates p-ERK1/2 and p-Akt in A549 cells. Blockade of either of these pathways with chemical inhibitors moderately sensitized A549 cells to cisplatin-induced apoptosis and reduced cell viability. Strikingly, concurrent inhibition of p-ERK1/2 and p-Akt significantly potentiated cisplatin cytotoxicity in vitro and in vivo. The sensitization of A549 cells to cisplatin cytotoxicity induced by p-Akt inhibition was mediated by the upregulation of PUMA, whereas that induced by p-ERK1/2 inhibition occurred by Bcl-2 downregulation. These data indicate that the cooperative effects of p-ERK1/2 and p-Akt on attenuating cisplatin cytotoxicity are mediated by PUMA and Bcl-2 regulation, and concurrently blocking these pathways may be an effective strategy for improving the efficacy of cisplatin as anticancer treatment.

Claudin-1 expression confers resistance to anoikis in colon cancer cells in a Src-dependent manner

Denial of the appropriate cell-matrix interaction in epithelial cells induces apoptosis and is called 'anoikis'. Cancer cells are resistant to anoikis and it is believed that the resistance to anoikis helps promote tumor malignancy especially metastasis. We and others have demonstrated that the expression of tight junction protein claudin-1 is highly upregulated in colorectal cancer (CRC) and helps promote tumor progression and metastasis. However, molecular mechanism/s underlying claudin-1-dependent regulation of CRC progression remains poorly understood. In current study, we have determined that claudin-1 expression modulates anoikis in colon cancer cells to influence colon cancer invasion and thus metastasis. We have further provided data that claudin-1 modulates anoikis in a Src-Akt-Bcl-2-dependent manner. Importantly, claudin-1 physically associates with Src/p-Src in a multiprotein complex that also includes ZO-1, a PDZ-binding tight junction protein. Taken together, our data support the role of claudin-1 in the regulation of CRC progression and suggest that the regulation of anoikis may serve as a key regulatory mechanism in claudin-1-dependent regulation of CRC progression. Our findings are of direct clinical relevance and may open new therapeutic opportunity in colon cancer treatment and/or management.

[Establishment of animal model of a human lung adenocarcinoma drug-resistant cell line Anip973/NVB and investigation on mechanism of drug resistance]

背景与目的

肿瘤的多药耐药性（multidrug resistance, MDR）是导致肺癌化疗失败的主要原因，长春瑞滨（Vinorelbine，诺维本，NVB）是治疗非小细胞肺癌最有效的化疗药物之一，本研究旨在建立人肺腺癌Anip973/NVB耐药细胞的动物模型，并初步探讨其耐药机制。

方法

采用皮下注射法建立人肺腺癌Anip973细胞和耐药细胞Anip973/NVB的裸鼠移植瘤模型，分成Anip973治疗组、Anip973对照组、Anip973/NVB治疗组、Anip973/NVB对照组。观察肿瘤生长情况，绘制生长曲线，计算抑瘤率；通过电镜观察移植瘤的细胞形态学变化；通过免疫组化法检测移植瘤中Bcl-2蛋白和MRP3蛋白的表达来进一步研究人肺腺癌Anip973/NVB细胞的耐药机制。

结果

与空白对照组比较，Anip973细胞和Anip973/NVB细胞移植瘤经NVB治疗后抑瘤率分别为60.00%、4.65%，Anip973/NVB细胞移植瘤生长受抑无统计学差异；电镜显示：经NVB治疗后，Anip973细胞出现特异性的凋亡形态学特征改变，而Anip973/NVB细胞仍然呈肿瘤细胞生长的典型形态。免疫组织化学染色结果显示：Bcl-2和MRP3蛋白在Anip973/NVB细胞移植瘤中的阳性表达率均明显高于在Anip973细胞移植瘤中的表达（P < 0.001）。

结论

Bcl-2及MRP3蛋白在Anip973/NVB耐药细胞裸鼠移植瘤内的高表达可能是该细胞系耐药的重要机制之一。

Nitrosothiol Signaling in Anoikis Resistance and Cancer Metastasis

Nitric oxide (NO) has been widely recognized as an important cell-signaling molecule that regulates various physiological and pathological processes. S-nitrosylation, or covalent attachment of NO to protein sulfhydryl groups, is a key mechanism by which NO regulates protein functions and cellular processes. In this article we discuss the various roles of NO and protein nitrosylation in cancer development, with a focus on cell invasion and anoikis resistance, both of which are key determinants of cancer metastasis. We specially address some of the mechanisms by which NO-mediated S-nitrosylation modulates substrates that have putative effects on key steps of metastasis. We propose that nitrosothiol signaling is a key regulatory mechanism common to several pathways involved in cancer progression and metastasis, and identifying such a mechanism will improve our understanding of the disease process and aid in the development of novel anticancer therapeutics.

Bcl-2 upregulation induced by miR-21 via a direct interaction is associated with apoptosis and chemoresistance in MIA PaCa-2 pancreatic cancer cells

BACKGROUND AND AIMS

Bcl-2 was previously shown to be associated with apoptosis and chemoresistance and carry multiple regulating pathways. However, the roles and mechanisms of miRNA (miR)-21 in regulation of Bcl-2 in pancreatic cancer remain to be elucidated. The aim of this study was to explore the regulation of Bcl-2 expression by miR-21 and its impact on apoptosis, chemoresistance and growth of pancreatic cancer cells using a pancreatic cancer cell line, MIA PaCa-2.

METHODS

miR-21 mimics and inhibitor were transfected to MIA PaCa-2 pancreatic cancer cells, respectively. Alteration in Bcl-2/Bax expression was subsequently evaluated. Then, luciferase activity was observed after miR-21 mimics and pRL-TK plasmids containing wild-type and mutant 3'UTRs of Bcl-2 mRNA were co-transfected. Finally, apoptosis, chemosensitivity to gemcitabine and cell proliferation were evaluated.

RESULTS

Upregulation of Bcl-2 expression was detected in cells transfected with miR-21 mimics, accompanied by downregulated Bax expression, less apoptosis, lower caspase-3 activity, decreased chemosensitivity to gemcitabine and increased proliferation compared with the control cells. Cells transfected with miR-21 inhibitor revealed an opposite trend. There was a significant increase in luciferase activity in the cells transfected with the wild-type pRL-TK plasmid, in contrast to those transfected with the mutant one, indicating that miR-21 promotes Bcl-2 expression by binding directly to the 3'UTR of Bcl-2 mRNA.

CONCLUSIONS

Upregulation of Bcl-2 directly induced by miR-21 is associated with apoptosis, chemoresistance and proliferation of MIA PaCa-2 pancreatic cancer cells.

MicroRNA-mediated regulation of pancreatic cancer cell proliferation

MicroRNAs (miRNAs) comprising 19-25 nucleotides are highly conserved small non-coding RNAs which regulate normal gene expression during development, cell proliferation and apoptosis by targeting mRNAs of protein-coding genes at the post-transcriptional level. Prevalent studies suggest that some human miRNAs, such as miRNA-16, are deregulated in human cancer and behave as tumor suppressors. The overall objective of our investigation was to assess whether miRNA-16 (miR-16) is involved in the regulation of critical genes, such as BCL2, that control the sensitivity of pancreatic cancer cells to apoptosis. This study showed that the ectopic overexpression of miR-16 may be therapeutically beneficial as is evidenced by impaired cell survival with concomitant attenuation of anti-apoptotic protein Bcl-2. Moreover, the luciferase reporter assay suggested that miR-16 post-transcriptionally regulates Bcl-2 expression in pancreatic cancer cells through the target sites of the 3' untranslated region of this gene.

Adhesion-mediated apoptosis resistance in cancer

Adhesion-mediated apoptosis resistance (AMAR) is an emerging concept that may explain the observed differences in survival between cells within the three-dimensional structure of a tumor and the standard monolayer culture conditions in the laboratory. Not only the cancer cells' motility and invasiveness are different in a three-dimensional tumor, but - crucially - the cells' sensitivity towards apoptosis, a form of programmed cell death, varies widely between the in vivo and in vitro situation. Tumor cells interacting either with a specific extracellular matrix protein substrate or with each other or with non-transformed cells, such as fibroblasts, exhibit increased resistance towards a wide variety of therapeutic approaches. In this review we discuss the molecular basis of these interactions and the main downstream effectors that are involved in the enhancement of the tumor cells' survival. In particular, we show that the pathways activated by adhesion are not unique, but involve the MAPK/ERK and PI3K/Akt pathways, which are reused between different forms of AMAR and are also found in adhesion-independent modes of resistance. Thus, the tools to overcome AMAR are already at our disposal and using them in this novel context of AMAR should lead to significant therapeutic benefit.