Torin2 targets dysregulated pathways in anaplastic thyroid cancer and inhibits tumor growth and metastasis

The Protective Role of Troxerutin (Trox) in Counteracting Anaplastic Thyroid Carcinoma (ATC) Progression

Anaplastic thyroid carcinoma (ATC) is a rare thyroid neoplasm characterized by aggressiveness and a high mortality rate. Troxerutin (Trox) is a bioflavonoid widely found in various fruits and vegetables with numerous protective effects, including anticancer activities. To evaluate the anti-oxidant and anti-inflammatory effect of Trox, in vitro and in vivo studies were conducted in a model of ATC. Human ATC 8305C cell lines were treated with increasing concentrations of Trox (10 μg/mL, 30 μg/mL, 100 μg/mL, 300 μg/mL), and our results revealed that Trox treatment was able to reduce the viability of ATC cells and migratory capacity, reducing the expression of anti-apoptotic factors, such as B-cell lymphoma (bcl-2), and increasing the expression of pro-apoptotic factors, such as Caspase-3 and BID, activating oxidative stress mediators, such as manganese superoxide dismutase (MnSOD), heme oxygenase-1 (HO-1), glutathione (GSH) and reactive oxygen species modulator 1 (ROMO-1). Furthermore, Trox modulates NF-κB pathway markers, such as NIK and TRAF-6. Further confirmation was obtained through in vivo studies, in which Trox treatment, at doses of 12.5, 25 and 50 mg/kg, reduced morphological alteration, decreasing mast cell accumulation. Therefore, the use of Trox could be considered a promising strategy to counteract the progression of ATC.

Anti-inflammatory effects of Torin2 on lipopolysaccharide-treated RAW264.7 murine macrophages and potential mechanisms

Context

Torin2 has various pharmacological properties. However, its anti-inflammatory activity has not been reported.

Objective

This study focused on the potential anti-inflammatory properties of Torin2 in lipopolysaccharide (LPS)-evoked RAW264.7 murine macrophages. The study aimed to shed light on the molecular mechanisms that ameliorate these effects.

Methods

Torin2 was applied to 100 ng/mL lipopolysaccharide-induced RAW 264.7 macrophages in vitro. Nitric oxide (NO) levels were detected using the Griess reagent kit. Prostaglandin E2 (PGE2), pro-inflammatory cytokines interleukin (IL)-1β, interleukin (IL)-6, and tumor necrosis factor in the supernatant fraction were determined using enzyme-linked immunosorbent assay (ELISA). Gene expression of pro-inflammatory cytokines, cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) were tested using real-time quantitative polymerase chain reaction (qPCR). Cyclooxygenase-2 and inducible nitric oxide synthase proteins, phosphorylation of mitogen-activated protein kinase (MAPK) subgroups, extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), p38, I-kappa-B-alpha (IκBα), and nuclear factor-kappa-B (NF-κB), and activation in extracts were detected via western blotting. Nuclear factor-kappa-B/p65 nuclear translocation was tested using an immunofluorescence assay.

Results

The results demonstrated that pre-treatment with Torin2 profoundly attenuated the lipopolysaccharide-stimulated levels of nitric oxide and prostaglandin E2, pro-inflammatory cytokines, messenger ribonucleic acid (mRNA), and protein expression of cyclooxygenase-2 and inducible nitric oxide synthase. Collectively, Torin2 pre-treatment notably weakened lipopolysaccharide-induced damage by reducing the phosphorylation of nuclear factor-kappa-B, p38, c-Jun N-terminal kinase, extracellular signal-regulated kinase proteins, and nuclear factor-kappa-B/p65 nuclear translocation.

Conclusion

Numerous pieces of evidence indicated that Torin2 reversed inflammatory activation by regulating nuclear factor-kappa-B and mitogen-activated protein kinase signaling pathways and provided a tentative potential candidate for preventing and treating inflammatory diseases.

Targeting the mTOR pathway using novel ATP‑competitive inhibitors, Torin1, Torin2 and XL388, in the treatment of glioblastoma

Mechanistic target of rapamycin (mTOR), which functions via two multiprotein complexes termed mTORC1 and mTORC2, is positioned in the canonical phosphoinositide 3-kinase-related kinase (PI3K)/AKT (PI3K/AKT) pathways. These complexes exert their actions by regulating other important kinases, such as 40S ribosomal S6 kinases (S6K), eukaryotic translation initiation factor 4E (elF4E)-binding protein 1 (4E-BP1) and AKT, to control cell growth, proliferation, migration and survival in response to nutrients and growth factors. Glioblastoma (GB) is a devastating form of brain cancer, where the mTOR pathway is deregulated due to frequent upregulation of the Receptor Tyrosine Kinase/PI3K pathways and loss of the tumor suppressor phosphatase and tensin homologue (PTEN). Rapamycin and its analogs were less successful in clinical trials for patients with GB due to their incomplete inhibition of mTORC1 and the activation of mitogenic pathways via negative feedback loops. Here, the effects of selective ATP-competitive dual inhibitors of mTORC1 and mTORC2, Torin1, Torin2 and XL388, are reported. Torin2 exhibited concentration-dependent pharmacodynamic effects on inhibition of phosphorylation of the mTORC1 substrates S6K^Ser235/236 and 4E-BP1^Thr37/46 as well as the mTORC2 substrate AKT^Ser473 resulting in suppression of tumor cell migration, proliferation and S-phase entry. Torin1 demonstrated similar effects, but only at higher doses. XL388 suppressed cell proliferation at a higher dose, but failed to inhibit cell migration. Treatment with Torin1 suppressed phosphorylation of proline rich AKT substrate of 40 kDa (PRAS40) at Threonine 246 (PRAS40^Thr246) whereas Torin2 completely abolished it. XL388 treatment suppressed the phosphorylation of PRAS40^Thr246 only at higher doses. Drug resistance analysis revealed that treatment of GB cells with XL388 rendered partial drug resistance, which was also seen to a lesser extent with rapamycin and Torin1 treatments. However, treatment with Torin2 completely eradicated the tumor cell population. These results strongly suggest that Torin2, compared to Torin1 or XL388, is more effective in suppressing mTORC1 and mTORC2, and therefore in the inhibition of the GB cell proliferation, dissemination and in overcoming resistance to therapy. These findings underscore the significance of Torin2 in the treatment of GB.

Research progress of mTOR inhibitors

Mammalian target of rapamycin (mTOR) is a highly conserved Serine/Threonine (Ser/Thr) protein kinase, which belongs to phosphatidylinositol-3-kinase-related kinase (PIKK) protein family. mTOR exists as two types of protein complex: mTORC1 and mTORC2, which act as central controller regulating processes of cell metabolism, growth, proliferation, survival and autophagy. The mTOR inhibitors block mTOR signaling pathway, producing anti-inflammatory, anti-proliferative, autophagy and apoptosis induction effects, thus mTOR inhibitors are mainly used in cancer therapy. At present, mTOR inhibitors are divided into four categories: Antibiotic allosteric mTOR inhibitors (first generation), ATP-competitive mTOR inhibitors (second generation), mTOR/PI3K dual inhibitors (second generation) and other new mTOR inhibitors (third generation). In this article, these four categories of mTOR inhibitors and their structures, properties and some clinical researches will be introduced. Among them, we focus on the structure of mTOR inhibitors and try to analyze the structure-activity relationship. mTOR inhibitors are classified according to their chemical structure and their contents are introduced systematically. Moreover, some natural products that have direct or indirect mTOR inhibitory activities are introduced together. In this article, we analyzed the target, binding mode and structure-activity relationship of each generation of mTOR inhibitors and proposed two hypothetic scaffolds (the inverted-Y-shape scaffold and the C-shape scaffold) for the second generation of mTOR inhibitors. These findings may provide some help or reference for drug designing, drug modification or the future development of mTOR inhibitor.

Torin2 inhibits the EGFR-TKI resistant Non-Small Lung Cancer cell proliferation through negative feedback regulation of Akt/mTOR signaling

It is known that mammalian target of rapamycin (mTOR) signaling plays an important role in NSCLC cells proliferation. Torin2 is a second-generation ATP-competitive inhibitor which is selective for mTOR activity. In this study, we investigated whether torin2 was effective against lung cancer cells, especially EGFR-TKIs resistant NSCLC cells. We found that torin2 dramatically inhibited EGFR-TKI resistant cells viability in vitro. In xenograft model, torin2 treatment significantly reduced the volume and weight of xenograft tumor in the erlotinib resistant PC9/E cells. Additionally, autophagy protein of phosphatidylethanolamine-modified microtubule-associated protein light-chain 3II/I (LC3II/I) increased in PC9/E after torin2 treatment. Torin2 blocked the level of phosphorylated S6 and the phosphorylation of Akt at both T308 and S473 sites compared with erlotinib treatment. Furthermore, TUNEL assay showed that apoptosis of tumor tissue increased significantly in the torin2 treatment group. Immunohistochemical analysis demonstrated that tumor angiogenesis was obviously inhibited by torin2 treatment in EGFR-TKI resistant group. Collectively, our results suggested that torin2 could inhibit the NSCLC cells proliferation by negative feedback regulation of Akt/mTOR signaling and inducing autophagy. This suggests that torin2 could be a novel therapeutic approach for EGFR-TKI resistant NSCLC.

Effects of metformin and pioglitazone combination on apoptosis and AMPK/mTOR signaling pathway in human anaplastic thyroid cancer cells

Anaplastic cancer constitutes 1% of thyroid cancers, and it is one of the most aggressive cancers. Treatment options are external radiation therapy and/or chemotherapy. The success rate with these treatment modalities is not satisfactory. We aimed to evaluate the effects of metformin (MET) and pioglitazone (PIO) combination on apoptosis and AMP-activated protein kinase/mammalian target of rapamycin (mTOR) signaling pathway in human anaplastic thyroid cancer cells. In this study, we evaluated the effects of MET and PIO individually and the combination of the two drugs on the cellular lines SW1736 and C643 ATC. Genes contained in the mTOR signaling pathway were examined using human mTOR Signalization RT² Profiler PCR Array. In C643 and SW1736 cell lines, IC₅₀ doses of MET and PIO were found out as 17.69 mM, 11.64 mM, 27.12 µM, and 23.17 µM. Also, the combination of MET and PIO was determined as an additive according to isobologram analyses. We have found the downregulation of the expression levels of oncogenic genes: AKT3, CHUK, CDC42, EIF4E, HIF1A, IKBKB, ILK, MTOR, PIK3CA, PIK3CG, PLD1, PRKCA, and RICTOR genes, in the MET and PIO combination-treated cells. In addition, expression levels of tumor suppressor genes, DDIT4, DDIT4L, EIF4EBP1, EIF4EBP2, FKBP1A, FKBP8, GSK3B, MYO1C, PTEN, ULK1, and ULK2, were found to have increased significantly. The MET + PIO combination was first applied to thyroid cancer cells, and significant reductions in the level of oncogenic genes were detected. The decreases, particularly, in AKT3, DEPTOR, EIF4E, ILK, MTOR, PIK3C, and PRKCA expressions indicate that progression can be prevented in thyroid cancer cells and these genes could be selected as therapeutic targets.

Metastatic propagation of thyroid cancer; organ tropism and major modulators

Thyroid cancer, as the most prevalent endocrine malignancy, comprises nearly 1% of all cancers in the world. The metastatic propagation of thyroid cancer is under the control of a number of modulating processes and factors such as signaling pathways and their components, cell division regulators, metabolic reprogramming factors, extracellular matrix remodelers, epithelial to mesenchymal transition modulators, epigenetic mechanisms, hypoxia and cytokines. Identifying the exact molecular mechanisms of these dysregulated processes could help to discover the key targets for therapeutic purposes and utilizing them as diagnostic, prognostic and predictors of the clinical course of patients. In this review article, we describe different aspects of thyroid cancer metastasis by focusing on defective genes and pathways involved in its metastatic spread.

Effect of mesoporous silica nanoparticles co‑loading with 17‑AAG and Torin2 on anaplastic thyroid carcinoma by targeting VEGFR2

Anaplastic thyroid carcinoma (ATC) is a highly aggressive tumor with a poor prognosis and a low median survival rate because of insufficient effective therapeutic modalities. Recently, mesoporous silica nanoparticles (MSNs) as a green non-toxic and safe nanomaterial have shown advantages to be a drug carrier and to modify the targeting group to the targeted therapy. To aim of the study was to explore the effects of MSNs co-loading with 17-allylamino-17-demethoxy-geldanamycin (17-AAG; HSP90 inhibitor) and 9-(6-aminopyridin-3-yl)-1-(3-(trifluoromethyl)phenyl)benzo[h][1,6]naphthyridin-2(1H)-one (Torin2; mTOR inhibitor) by targeting vascular endothelial growth factor receptor 2 (VEGFR2) on the viability of human anaplastic thyroid carcinoma FRO cells. The cytotoxicity of 17-AAG and Torin2 were analyzed by MTT assay. The possible synergistic antitumor effects between 17-AAG and Torin2 were evaluated by CompuSyn software. Flow cytometry was performed to assess the VEGFR2 targeting of (17-AAG+Torin2)@MSNs-anti-VEGFR2 ab and uptake by FRO cells. An ATC xenograft mouse model was established to assess the antitumor effect of (17-AAG+Torin2)@MSNs-anti-VEGFR2 ab in vivo. The results revealed that the combination of 17-AAG and Torin2 inhibited the growth of FRO cells more effectively compared with single use of these agents. Additionally, the synergistic antitumor effect appeared when concentration ratio of the two drugs was 1:1 along with total drug concentration greater than 0.52 µM. Furthermore, in an ATC animal model, it was revealed that the (17-AAG+Torin2)@MSNs-anti-VEGFR2 ab therapy modality could most effectively prolong the median survival time [39.5 days vs. 33.0 days (non-targeted) or 27.5 days (control)]. Compared to (17-AAG+Torin2)@MSNs, the (17-AAG+Torin2)@MSNs-anti-VEGFR2 ab could not only inhibit ATC cell growth but also prolong the median survival time of tumor-bearing mice in vivo and vitro more effectively, which may provide a new promising therapy for ATC.

The role of RICTOR amplification in targeted therapy and drug resistance

The emergence of tyrosine kinase inhibitors (TKIs) has changed the current treatment paradigm and achieved good results in recent decades. However, an increasing number of studies have indicated that the complex network of receptor tyrosine kinase (RTK) co-activation could influence the characteristic phenotypes of cancer and the tumor response to targeted treatments. One of strategies to blocking RTK co-activation is targeting the downstream factors of RTK, such as PI3K-AKT-mTOR pathway. RICTOR, a core component of mTORC2, acts as a key effector molecule of the PI3K-AKT pathway; its amplification is often associated with poor clinical outcomes and resistance to TKIs. Here, we discuss the biology of RICTOR in tumor and the prospects of targeting RICTOR as a complementary therapy to inhibit RTK co-activation.

A Combinatorial Strategy for Targeting BRAF V600E-Mutant Cancers with BRAFV600E Inhibitor (PLX4720) and Tyrosine Kinase Inhibitor (Ponatinib)

PURPOSE

Most aggressive thyroid cancers are commonly associated with a BRAF ^V600E mutation. Preclinical and clinical data in BRAF ^V600E cancers suggest that combined BRAF and MEK inhibitor treatment results in a response, but resistance is common. One mechanism of acquired resistance is through persistent activation of tyrosine kinase (TK) signaling by alternate pathways. We hypothesized that combination therapy with BRAF and multitargeting TK inhibitors (MTKI) might be more effective in BRAF ^V600E thyroid cancer than in single-agent or BRAF and MEK inhibitors.

EXPERIMENTAL DESIGN

The combined drug activity was analyzed to predict any synergistic effect using high-throughput screening (HTS) of active drugs. We performed follow-up in vitro and in vivo studies to validate and determine the mechanism of action of synergistic drugs.

RESULTS

The MTKI ponatinib and the BRAF inhibitor PLX4720 showed synergistic activity by HTS. This combination significantly inhibited proliferation, colony formation, invasion, and migration in BRAF ^V600E thyroid cancer cell lines and downregulated pERK/MEK and c-JUN signaling pathways, and increased apoptosis. PLX4720-resistant BRAF ^V600E cells became sensitized to the combination treatment, with decreased proliferation at lower PLX4720 concentrations. In an orthotopic thyroid cancer mouse model, combination therapy significantly reduced tumor growth (P < 0.05), decreased the number of metastases (P < 0.05), and increased survival (P < 0.05) compared with monotherapy and vehicle control.

CONCLUSIONS

Combination treatment with ponatinib and PLX4720 exhibited significant synergistic anticancer activity in preclinical models of BRAF ^V600E thyroid cancer, in addition to overcoming PLX4720 resistance. Our results suggest this combination should be tested in clinical trials.

New Therapies for Advanced Thyroid Cancer

Thyroid cancer is the most common endocrine cancer. The discovery of new biomarkers for thyroid cancer has significantly improved the understanding of the molecular pathogenesis of thyroid cancer, thus allowing more personalized treatments for patients with thyroid cancer. Most of the recently discovered targeted therapies inhibit the known oncogenic mechanisms in thyroid cancer initiation and progression such as MAPK pathway, PI3K/Akt-mTOR pathways, or VEGF. Despite the significant advances in molecular testing and the discoveries of new and promising therapeutics, effective treatments for advanced and metastatic, iodine-refractory thyroid cancer are still lacking. Here, we aim to summarize the current understanding of the genetic alterations and the dysregulated pathways in thyroid cancer and to discuss the most recent targeted therapies and immunotherapy for advanced thyroid cancer with a promising anti-tumor activity and clinical benefit.

mTOR Links Tumor Immunity and Bone Metabolism: What are the Clinical Implications?

Phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) plays a crucial role in the control of cellular growth, proliferation, survival, metabolism, angiogenesis, transcription, and translation. In most human cancers, alterations to this pathway are common and cause activation of other downstream signaling pathways linked with oncogenesis. The mTOR pathway modulates the interactions between the stroma and the tumor, thereby affecting both tumor immunity and angiogenesis. Inflammation is a hallmark of cancer, playing a central role in the tumor dynamics, and immune cells can exert antitumor functions or promote the growth of cancer cells. In this context, mTOR may regulate the activity of macrophages and T cells by regulating the expression of cytokines/chemokines, such as interleukin (IL)-10 and transforming growth factor (TGF-β), and/or membrane receptors, such as cytotoxic T-Lymphocyte protein 4 (CTLA-4) and Programmed Death 1 (PD-1). Furthermore, inhibitors of mammalian target of rapamycin are demonstrated to actively modulate osteoclastogenesis, exert antiapoptotic and pro-differentiative activities in osteoclasts, and reduce the number of lytic bone metastases, increasing bone mass in tumor-bearing mice. With regard to the many actions in which mTOR is involved, the aim of this review is to describe its role in the immune system and bone metabolism in an attempt to identify the best strategy for therapeutic opportunities in the metastatic phase of solid tumors.

Mouse models of thyroid cancer: Bridging pathogenesis and novel therapeutics

Due to a global increase in the incidence of thyroid cancer, numerous novel mouse models were established to reveal thyroid cancer pathogenesis and test promising therapeutic strategies, necessitating a comprehensive review of translational medicine that covers (i) the role of mouse models in the research of thyroid cancer pathogenesis, and (ii) preclinical testing of potential anti-thyroid cancer therapeutics. The present review article aims to: (i) describe the current approaches for mouse modeling of thyroid cancer, (ii) provide insight into the biology and genetics of thyroid cancers, and (iii) offer guidance on the use of mouse models for testing potential therapeutics in preclinical settings. Based on research with mouse models of thyroid cancer pathogenesis involving the RTK, RAS/RAF/MEK/ERK, PI3K/AKT/mTOR, SRC, and JAK-STAT signaling pathways, inhibitors of VEGFR, MEK, mTOR, SRC, and STAT3 have been developed as anti-thyroid cancer drugs for "bench-to-bedside" translation. In the future, mouse models of thyroid cancer will be designed to be ''humanized" and "patient-like," offering opportunities to: (i) investigate the pathogenesis of thyroid cancer through target screening based on the CRISPR/Cas system, (ii) test drugs based on new mouse models, and (iii) explore the underlying mechanisms based on multi-omics.

Therapeutic advances in anaplastic thyroid cancer: a current perspective

Thyroid cancer incidence is increasing at an alarming rate, almost tripling every decade. In 2017, it was the fifth most common cancer in women. Although the majority of thyroid tumors are curable, about 2-3% of thyroid cancers are refractory to standard treatments. These undifferentiated, highly aggressive and mostly chemo-resistant tumors are phenotypically-termed anaplastic thyroid cancer (ATC). ATCs are resistant to standard therapies and are extremely difficult to manage. In this review, we provide the information related to current and recently emerged first-line systemic therapy (Dabrafenib and Trametinib) along with promising therapeutics which are in clinical trials and may be incorporated into clinical practice in the future. Different categories of promising therapeutics such as Aurora kinase inhibitors, multi-kinase inhibitors, epigenetic modulators, gene therapy using oncolytic viruses, apoptosis-inducing agents, and immunotherapy are reviewed. Combination treatment options that showed synergistic and antagonistic effects are also discussed. We highlight ongoing clinical trials in ATC and discuss how personalized medicine is crucial to design the second line of treatment. Besides using conventional combination therapy, embracing a personalized approach based on advanced genomics and proteomics assessment will be crucial to developing a tailored treatment plan to improve the chances of clinical success.

mTOR Pathway in Papillary Thyroid Carcinoma: Different Contributions of mTORC1 and mTORC2 Complexes for Tumor Behavior and SLC5A5 mRNA Expression

The mammalian target of rapamycin (mTOR) pathway is overactivated in thyroid cancer (TC). We previously demonstrated that phospho-mTOR expression is associated with tumor aggressiveness, therapy resistance, and lower mRNA expression of SLC5A5 in papillary thyroid carcinoma (PTC), while phospho-S6 (mTORC1 effector) expression was associated with less aggressive clinicopathological features. The distinct behavior of the two markers led us to hypothesize that mTOR activation may be contributing to a preferential activation of the mTORC2 complex. To approach this question, we performed immunohistochemistry for phospho-AKT Ser473 (mTORC2 effector) in a series of 182 PTCs previously characterized for phospho-mTOR and phospho-S6 expression. We evaluated the impact of each mTOR complex on SLC5A5 mRNA expression by treating cell lines with RAD001 (mTORC1 blocker) and Torin2 (mTORC1 and mTORC2 blocker). Phospho-AKT Ser473 expression was positively correlated with phospho-mTOR expression. Nuclear expression of phospho-AKT Ser473 was significantly associated with the presence of distant metastases. Treatment of cell lines with RAD001 did not increase SLC5A5 mRNA levels, whereas Torin2 caused a ~6 fold increase in SLC5A5 mRNA expression in the TPC1 cell line. In PTC, phospho-mTOR activation may lead to the activation of the mTORC2 complex. Its downstream effector, phospho-AKT Ser473, may be implicated in distant metastization, therapy resistance, and downregulation of SLC5A5 mRNA expression.

The CDK4/6 inhibitor LY2835219 has potent activity in combination with mTOR inhibitor in head and neck squamous cell carcinoma

Deletion of CDKN2A (p16) or amplification of CCND1 (cyclin D1) occurs commonly in head and neck squamous cell carcinoma (HNSCC) and induces sustained cyclin-dependent kinase (CDK) 4/6 activation. Here, we report the antiproliferative activity of LY2835219, a selective CDK4/6 inhibitor through inhibition of CDK4/6-dependent Ser780 phosphorylation in retinoblastoma (RB) and induction of cell cycle arrest in HNSCC cells. In addition, we demonstrated the antitumor effects of HNSCC xenografts to LY2835219 in vivo. Given the limited effect in HNSCC as a single-agent treatment with LY2835219, a combinational strategy is required to enhance antitumor activity. At the molecular level, we found that LY2835219 inhibited activation of AKT and ERK, but not mTOR. The combination of LY2835219 with mTOR inhibitor was found to be more effective than either drug alone in vitro and in vivo. Taken together, our findings suggest that a combinational treatment with LY2835219 and mTOR inhibitor is a promising therapeutic approach for HNSCC.

Carfilzomib potentiates CUDC-101-induced apoptosis in anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is one of the most aggressive human malignancies, with no effective treatment currently available. Previously, we identified agents active against ATC cells, both in vitro and in vivo, using quantitative high-throughput screening of 3282 clinically approved drugs and small molecules. Here, we report that combining two of these active agents, carfilzomib, a second-generation proteasome inhibitor, and CUDC-101, a histone deacetylase and multi-kinase inhibitor, results in increased, synergistic activity in ATC cells. The combination of carfilzomib and CUDC-101 synergistically inhibited cellular proliferation and caused cell death in multiple ATC cell lines harboring various driver mutations observed in human ATC tumors. This increased anti-ATC effect was associated with a synergistically enhanced G2/M cell cycle arrest and increased caspase 3/7 activity induced by the drug combination. Mechanistically, treatment with carfilzomib and CUDC-101 increased p21 expression and poly (ADP-ribose) polymerase protein cleavage. Our results suggest that combining carfilzomib and CUDC-101 would offer an effective therapeutic strategy to treat ATC.

Torin2 enhances the radiosensitivity of MCF‑7 breast cancer cells by downregulating the mTOR signaling pathway and ATM phosphorylation

Radiotherapy has an important role in the comprehensive treatment of breast cancer. However, the clinical outcome of adjuvant radiotherapy may be limited due to intrinsic radioresistance, it is necessary to explore efficient radiosensitization methods that improve the clinical outcome of patients undergoing radiotherapy. The present study aimed to investigate whether the novel mechanistic target of rapamycin (mTOR) inhibitor Torin2 enhances the radiosensitivity of MCF‑7 breast cancer cells. A Cell Counting Kit‑8 (CCK‑8) assay was performed to measure the effect of Torin2 on cell proliferation, while clonogenic assays were employed to determine the effect of Torin2 in combination with radiation on the proliferation of MCF‑7 cells. The effect of Torin2 and/or radiation on the cell cycle was analyzed using flow cytometry. Furthermore, the protein expression of components of the phosphatidylinositol 3‑kinase/Akt/mTOR pathway, and the expression of proteins involved in DNA damage repair, was measured by western blot analysis. The results demonstrated that Torin2 exhibited a higher potency in MCF‑7 cells, while MDA‑MB‑231 cells were less sensitive to Torin2. Compared with irradiation alone, pretreatment with 20 nM Torin2 followed by irradiation resulted in an increased level of γ‑H2A histone family member X. Radiation induced the activation of the Akt/mTOR signaling pathway and upregulated the expression of phosphorylated (p)‑Akt473 and p‑eukaryotic translation initiation factor 4E binding protein 1 (4EBP1)37/46. Notably, pretreatment with Torin2 attenuated the radiation‑induced activation of the Akt/mTOR signaling pathway. In addition, Torin2 partially blocked the repair of double‑strand breaks induced by radiation by reducing the activation of ataxia telangiectasia‑mutated, and sensitized MCF‑7 cells to radiation. In conclusion, administration of Torin2 prior to irradiation enhanced the radiotherapeutic effect on breast cancer cells in vitro, and these results may provide a foundation for the rational use of combined therapy with irradiation and Torin2 for breast cancer in clinical practice.

CAR T Therapy Targeting ICAM-1 Eliminates Advanced Human Thyroid Tumors

Purpose: Poorly differentiated thyroid cancer and anaplastic thyroid cancer (ATC) are rare yet lethal malignancies with limited treatment options. Many malignant tumors, including papillary thyroid cancer (PTC) and ATC, are associated with increased expression of ICAM-1, providing a rationale for utilizing ICAM-1-targeting agents for the treatment of aggressive cancer. We developed a third-generation chimeric antigen receptor (CAR) targeting ICAM-1 to leverage adoptive T-cell therapy as a new treatment modality.Experimental Design: ICAM-1 CAR T cells were applied to multiple malignant and nonmalignant target cells to investigate specific target cell death and "off-tumor" toxicity in vitroIn vivo therapeutic efficacy of ICAM-1 CAR T cells was examined in ATC mouse models established from a cell line and patient-derived tumors that rapidly develop systemic metastases.Results: ICAM-1 CAR T cells demonstrated robust and specific killing of PTC and ATC cell lines in vitro Interestingly, although certain ATC cell lines showed heterogeneous levels of ICAM-1 expression, addition of cytotoxic CAR T cells induced increased ICAM-1 expression such that all cell lines became targetable. In mice with systemic ATC, a single administration of ICAM-1 CAR T cells mediated profound tumor killing that resulted in long-term remission and significantly improved survival. Patient-derived ATC cells overexpressed ICAM-1 and were largely eliminated by autologous ICAM-1 CAR T cells in vitro and in animal models.Conclusions: Our findings are the first demonstration of CAR T therapy against both a metastatic, thyroid cancer cell line and advanced ATC patient-derived tumors that exhibit dramatic therapeutic efficacy and survival benefit in animal studies. Clin Cancer Res; 23(24); 7569-83. ©2017 AACR.

Metronomic Cordycepin Therapy Prolongs Survival of Oral Cancer-Bearing Mice and Inhibits Epithelial-Mesenchymal Transition

Cordycepin (3'-deoxyadenosine) is a natural compound abundantly found in Cordyceps sinesis in natural and fermented sources. In this study, we examined the effects of cordycepin in a human oral squamous cell carcinoma (OSCC) xenograft model. Cordycepin was administered in a regular, low-dose and prolonged schedule metronomic therapy. Two doses of cordycepin (25 mg/kg, 50 mg/kg) were administrated five days a week for eight consecutive weeks. The tumor volumes were reduced and survival time was significantly prolonged from 30.3 ± 0.9 days (control group) to 56 days (50 mg/kg group, the day of tumor-bearing mice were sacrificed for welfare consideration). The weights of mice did not change and liver, renal, and hematologic functions were not compromised. Cordycepin inhibited the OSCC cell viability in vitro (IC50 122.4-125.2 μM). Furthermore, morphological characteristics of apoptosis, increased caspase-3 activity and G2/M cell cycle arrest were observed. In wound healing assay, cordycepin restrained the OSCC cell migration. Cordycepin upregulated E-cadherin and downregulated N-cadherin protein expression, implying inhibition of epithelial-mesenchymal transition (EMT). The immunohistochemical staining of xenograft tumor with E-cadherin and vimentin validated in vitro results. In conclusion, metronomic cordycepin therapy showed effective tumor control, prolonged survival and low toxicities. Cytotoxicity against cancer cells with apoptotic features and EMT inhibition were observed.