Preclinical trial of a new dual mTOR inhibitor, MLN0128, using renal cell carcinoma tumorgrafts

Targeting mTOR as a Cancer Therapy: Recent Advances in Natural Bioactive Compounds and Immunotherapy

The mammalian target of rapamycin (mTOR) is a highly conserved serine/threonine-protein kinase, which regulates many biological processes related to metabolism, cancer, immune function, and aging. It is an essential protein kinase that belongs to the phosphoinositide-3-kinase (PI3K) family and has two known signaling complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). Even though mTOR signaling plays a critical role in promoting mitochondria-related protein synthesis, suppressing the catabolic process of autophagy, contributing to lipid metabolism, engaging in ribosome formation, and acting as a critical regulator of mRNA translation, it remains one of the significant signaling systems involved in the tumor process, particularly in apoptosis, cell cycle, and cancer cell proliferation. Therefore, the mTOR signaling system could be suggested as a cancer biomarker, and its targeting is important in anti-tumor therapy research. Indeed, its dysregulation is involved in different types of cancers such as colon, neck, cervical, head, lung, breast, reproductive, and bone cancers, as well as nasopharyngeal carcinoma. Moreover, recent investigations showed that targeting mTOR could be considered as cancer therapy. Accordingly, this review presents an overview of recent developments associated with the mTOR signaling pathway and its molecular involvement in various human cancer types. It also summarizes the research progress of different mTOR inhibitors, including natural and synthetised compounds and their main mechanisms, as well as the rational combinations with immunotherapies.

Identification of New Vulnerabilities in Conjunctival Melanoma Using Image-Based High Content Drug Screening

Recent evidence suggests that numerous similarities exist between the genomic landscapes of both conjunctival and cutaneous melanoma. Since alterations of several components of the MAP kinases, PI3K/mTOR, and cell cycle pathways have been reported in conjunctival melanoma, we decided to assess the sensitivity of conjunctival melanoma to targeted inhibition mostly of kinase inhibitors. A high content drug screening assay based on automated fluorescence microscopy was performed in three conjunctival melanoma cell lines with different genomic backgrounds with 489 kinase inhibitors and 53 other inhibitors. IC50 and apoptosis induction were respectively assessed for 53 and 48 compounds. The genomic background influenced the response to MAK and PI3K/mTOR inhibition, more specifically cell lines with BRAF V600E mutations were more sensitive to BRAF/MEK inhibition, while CRMM2 bearing the NRASQ61L mutation was more sensitive to PI3k/mTOR inhibition. All cell lines demonstrated sensitivity to cell cycle inhibition, being more pronounced in CRMM2, especially with polo-like inhibitors. Our data also revealed new vulnerabilities to Hsp90 and Src inhibition. This study demonstrates that the genomic background partially influences the response to targeted therapy and uncovers a large panel of potential vulnerabilities in conjunctival melanoma that may expand available options for the management of this tumor.

Preclinical evaluation of the dual mTORC1/2 inhibitor sapanisertib in combination with cisplatin in nasopharyngeal carcinoma

A wide range of investigational drugs are being investigated in clinical trials for the treatment of nasopharyngeal carcinoma (NPC), including PI3K-mTOR inhibitor. The purpose of this study was to evaluate the effective combination of TORC1/2 inhibitor sapanisertib and chemotherapy drug cisplatin in preclinical models of NPC. In our work, sapanisertib at nanomolar concentrations decreases viability and proliferation in NPC cells regardless of varying genetic backgrounds. Sapanisertib acts synergistically with cisplatin via induces more G0/G1 arrest and apoptosis. At the same concentration, sapanisertib neither decreases viability nor proliferation in normal nasal epithelial cells. Sapanisertib also decreases NPC cell migration. It decreases phosphorylation of Akt, mTOR, p70S6K and 4EBP1 in NPC cells. The in vitro findings on the inhibitory effects of sapanisertib on NPC growth and mTOR signaling were also evident in the NPC xenograft mouse model. In addition, combination of sapanisertib with cisplatin resulted in better efficacy than monotherapy to inhibit NPC growth in mice without causing significant toxicity. These data clearly demonstrate efficacy and insignificant toxicity of sapanisertib alone and its combination with cisplatin in NPC preclinical models. Our findings will accelerate clinical trials evaluating combination of sapanisertib and chemotherapy for NPC treatment.

Inhibition of the HIF-1 Survival Pathway as a Strategy to Augment Photodynamic Therapy Efficacy

Photodynamic therapy (PDT) is a non-to-minimally invasive treatment modality that utilizes photoactivatable drugs called photosensitizers to disrupt tumors with locally photoproduced reactive oxygen species (ROS). Photosensitizer activation by light results in hyperoxidative stress and subsequent tumor cell death, vascular shutdown and hypoxia, and an antitumor immune response. However, sublethally afflicted tumor cells initiate several survival mechanisms that account for decreased PDT efficacy. The hypoxia inducible factor 1 (HIF-1) pathway is one of the most effective cell survival pathways that contributes to cell recovery from PDT-induced damage. Several hundred target genes of the HIF-1 heterodimeric complex collectively mediate processes that are involved in tumor cell survival directly and indirectly (e.g., vascularization, glucose metabolism, proliferation, and metastasis). The broad spectrum of biological ramifications culminating from the activation of HIF-1 target genes reflects the importance of HIF-1 in the context of therapeutic recalcitrance. This chapter elaborates on the involvement of HIF-1 in cancer biology, the hypoxic response mechanisms, and the role of HIF-1 in PDT. An overview of inhibitors that either directly or indirectly impede HIF-1-mediated survival signaling is provided. The inhibitors may be used as pharmacological adjuvants in combination with PDT to augment therapeutic efficacy.

A Phase 1 Study of Sapanisertib (TAK-228) in East Asian Patients with Advanced Nonhematological Malignancies

BACKGROUND

Sapanisertib is an oral, highly selective inhibitor of mammalian target of rapamycin complexes 1 and 2.

OBJECTIVE

The aim of this study was to assess the safety, tolerability, pharmacokinetics, preliminary efficacy, and to establish the recommended phase 2 dose (RP2D) of sapanisertib.

PATIENTS AND METHODS

In this dose-escalation and expansion study, East Asian patients with nonhematologic malignancies received increasing sapanisertib doses once-daily (QD; starting at 2 mg) or once-weekly (QW; starting at 20 mg) in 28-day cycles.

RESULTS

Among 28 patients (QD dosing, n = 22; QW dosing, n = 6), three dose-limiting toxicities were reported (stomatitis [n = 2], gastrointestinal inflammation, gingivitis, and acute myocardial infarction [all n = 1]), all in the 4 mg QD cohort. The RP2D of sapanisertib was 3 mg QD. The most common adverse events were stomatitis (64%), nausea (50%), and decreased appetite (50%) in the QD arm, and nausea (100%), blood alkaline phosphatase increased (67%), and hyperglycemia (67%) in the QW arm. The T_max of sapanisertib was ~ 0.5-2.6 h and the T_1/2 was ~ 5.9-7.6 h. Three patients achieved stable disease for ≥ 6 months (1 each in 3 mg QD, 4 mg QD and 20 mg QW cohorts, respectively); the clinical benefit rate was 45% and 67% in the QD and QW arms, respectively.

CONCLUSIONS

The RP2D of sapanisertib in East Asian patients (3 mg QD) was lower than in Western patients (4 mg QD), but the pharmacokinetics and safety profiles were similar. Sapanisertib was well tolerated and showed moderate anti-tumor effects in heavily pretreated patients with nonhematologic malignancies.

NCT NUMBER

NCT03370302; Registered December 7, 2017.

A renal cell carcinoma tumorgraft platform to advance precision medicine

Renal cell carcinoma (RCC) encompasses a heterogenous group of tumors, but representative preclinical models are lacking. We previously showed that patient-derived tumorgraft (TG) models recapitulate the biology and treatment responsiveness. Through systematic orthotopic implantation of tumor samples from 926 ethnically diverse individuals into non-obese diabetic (NOD)/severe combined immunodeficiency (SCID) mice, we generate a resource comprising 172 independently derived, stably engrafted TG lines from 148 individuals. TG lines are characterized histologically and genomically (whole-exome [n = 97] and RNA [n = 102] sequencing). The platform features a variety of histological and oncogenotypes, including TCGA clades further corroborated through orthogonal metabolomic analyses. We illustrate how it enables a deeper understanding of RCC biology; enables the development of tissue- and imaging-based molecular probes; and supports advances in drug development.

Mechanistic Target of Rapamycin Inhibitors in Renal Cell Carcinoma: Potential, Limitations, and Perspectives

Several elements highlight the importance of the mechanistic target of rapamycin (mTOR) in the biology of renal cell carcinoma (RCC). mTOR signaling pathway is indeed frequently activated in RCC, inducing cancer cell proliferation and survival. In addition, mTOR promotes tumor angiogenesis and regulates the expression of hypoxia-inducible factors that play an important role in a subset of RCC. Despite mTOR protumorigenic effects, mTOR inhibitors have failed to provide long-lasting anticancer benefits in RCC patients, highlighting the need to readdress their role in the treatment of RCC. This review aims to present the rationale and limitations of targeting mTOR in RCC. Future roles of mTOR inhibitors in the treatment of RCC are also discussed, in particular in the context of immunotherapies.

Differential alternative RNA splicing and transcription events between tumors from African American and White patients in The Cancer Genome Atlas

Individuals of African ancestry suffer disproportionally from higher incidence, aggressiveness, and mortality for particular cancers. This disparity likely results from an interplay among differences in multiple determinants of health, including differences in tumor biology. We used The Cancer Genome Atlas (TCGA) SpliceSeq and TCGA aggregate expression datasets and identified differential alternative RNA splicing and transcription events (ARS/T) in cancers between self-identified African American (AA) and White (W) patients. We found that retained intron events were enriched among race-related ARS/T. In addition, on average, 12% of the most highly ranked race-related ARS/T overlapped between any two analyzed cancers. Moreover, the genes undergoing race-related ARS/T functioned in cancer-promoting pathways, and a number of race-related ARS/T were associated with patient survival. We built a web-application, CanSplice, to mine genomic datasets by self-identified race. The race-related targets have the potential to aid in the development of new biomarkers and therapeutics to mitigate cancer disparity.

Phase 1 study of mTORC1/2 inhibitor sapanisertib (TAK-228) in advanced solid tumours, with an expansion phase in renal, endometrial or bladder cancer

Background

This Phase 1 dose-escalation/expansion study assessed safety/tolerability of sapanisertib, an oral, highly selective inhibitor of mTORC1/mTORC2, in advanced solid tumours.

Methods

Eligible patients received increasing sapanisertib doses once daily (QD; 31 patients), once weekly (QW; 30 patients), QD for 3 days on/4 days off QW (QD × 3dQW; 33 patients) or QD for 5 days on/2 days off QW (QD × 5dQW; 22 patients). In expansion cohorts, 82 patients with renal cell carcinoma (RCC), endometrial or bladder cancer received sapanisertib 5 mg QD (39 patients), 40 mg QW (26 patients) or 30 mg QW (17 patients).

Results

Maximum tolerated doses of sapanisertib were 6 mg QD, 40 mg QW, 9 mg QD × 3dQW and 7 mg QD × 5dQW. Frequent dose-limiting toxicities (DLTs) included hyperglycaemia, maculo-papular rash (QD), asthenia and stomatitis (QD × 3dQW/QD × 5dQW); expansion phase doses of 5 mg QD and 30 mg QW were selected based on tolerability beyond the DLT evaluation period. One patient with RCC achieved complete response; nine experienced partial responses (RCC: seven patients; carcinoid tumour/endometrial cancer: one patient each). Sapanisertib pharmacokinetics were time-linear and supported multiple dosing. Pharmacodynamic findings demonstrated treatment-related reductions in TORC1/2 biomarkers.

Conclusions

Sapanisertib demonstrated a manageable safety profile, with preliminary antitumour activity observed in RCC and endometrial cancer.

Clinical trial registration

ClinicalTrials.gov, NCT01058707.

Preclinical and Dose-Finding Phase I Trial Results of Combined Treatment with a TORC1/2 Inhibitor (TAK-228) and Aurora A Kinase Inhibitor (Alisertib) in Solid Tumors

PURPOSE

The purpose of this study was to evaluate the rational combination of TORC1/2 inhibitor TAK-228 and Aurora A kinase inhibitor alisertib in preclinical models of triple-negative breast cancer (TNBC) and to conduct a phase I dose escalation trial in patients with advanced solid tumors.

EXPERIMENTAL DESIGN

TNBC cell lines and patient-derived xenograft (PDX) models were treated with alisertib, TAK-228, or the combination and evaluated for changes in proliferation, cell cycle, mTOR pathway modulation, and terminal cellular fate, including apoptosis and senescence. A phase I clinical trial was conducted in patients with advanced solid tumors treated with escalating doses of alisertib and TAK-228 using a 3+3 design to determine the maximum tolerated dose (MTD).

RESULTS

The combination of TAK-228 and alisertib resulted in decreased proliferation and cell-cycle arrest in TNBC cell lines. Treatment of TNBC PDX models resulted in significant tumor growth inhibition and increased apoptosis with the combination. In the phase I dose escalation study, 18 patients with refractory solid tumors were enrolled. The MTD was alisertib 30 mg b.i.d. days 1 to 7 of a 21-day cycle and TAK-228 2 mg daily, continuous dosing. The most common treatment-related adverse events were neutropenia, fatigue, nausea, rash, mucositis, and alopecia.

CONCLUSIONS

The addition of TAK-228 to alisertib potentiates the antitumor activity of alisertib in vivo, resulting in increased cell death and apoptosis. The combination is tolerable in patients with advanced solid tumors and should be evaluated further in expansion cohorts with additional pharmacodynamic assessment.

Oxygen: viral friend or foe?

The oxygen levels organ and tissue microenvironments vary depending on the distance of their vasculature from the left ventricle of the heart. For instance, the oxygen levels of lymph nodes and the spleen are significantly lower than that in atmospheric air. Cellular detection of oxygen and their response to low oxygen levels can exert a significant impact on virus infection. Generally, viruses that naturally infect well-oxygenated organs are less able to infect cells under hypoxic conditions. Conversely, viruses that infect organs under lower oxygen tensions thrive under hypoxic conditions. This suggests that in vitro experiments performed exclusively under atmospheric conditions ignores oxygen-induced modifications in both host and viral responses. Here, we review the mechanisms of how cells adapt to low oxygen tensions and its impact on viral infections. With growing evidence supporting the role of oxygen microenvironments in viral infections, this review highlights the importance of factoring oxygen concentrations into in vitro assay conditions. Bridging the gap between in vitro and in vivo oxygen tensions would allow for more physiologically representative insights into viral pathogenesis.

Patient-Derived Xenograft Models in Urological Malignancies: Urothelial Cell Carcinoma and Renal Cell Carcinoma

The engraftment of human tumor tissues into immunodeficient host mice to generate patient-derived xenograft (PDX) models has become increasingly utilized for many types of cancers. By capturing the unique genomic and molecular properties of the parental tumor, PDX models enable analysis of patient-specific clinical responses. PDX models are an important platform to address the contribution of inter-tumoral heterogeneity to therapeutic sensitivity, tumor evolution, and the mechanisms of treatment resistance. With the increasingly important role played by targeted therapies in urological malignancies, the establishment of representative PDX models can contribute to improved facilitation and adoption of precision medicine. In this review of the evolving role of the PDX in urothelial cancer and kidney cancer, we discuss the essential elements of successful graft development, effective translational application, and future directions for clinical models.

Systematic Review of Patient-Derived Xenograft Models for Preclinical Studies of Anti-Cancer Drugs in Solid Tumors

Patient-derived xenograft (PDX) models are used as powerful tools for understanding cancer biology in PDX clinical trials and co-clinical trials. In this systematic review, we focus on PDX clinical trials or co-clinical trials for drug development in solid tumors and summarize the utility of PDX models in the development of anti-cancer drugs, as well as the challenges involved in this approach, following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Recently, the assessment of drug efficacy by PDX clinical and co-clinical trials has become an important method. PDX clinical trials can be used for the development of anti-cancer drugs before clinical trials, with their efficacy assessed by the modified response evaluation criteria in solid tumors (mRECIST). A few dozen cases of PDX models have completed enrollment, and the efficacy of the drugs is assessed by 1 × 1 × 1 or 3 × 1 × 1 approaches in the PDX clinical trials. Furthermore, co-clinical trials can be used for personalized care or precision medicine with the evaluation of a new drug or a novel combination. Several PDX models from patients in clinical trials have been used to assess the efficacy of individual drugs or drug combinations in co-clinical trials.

Patient-derived xenograft models to optimize kidney cancer therapies

Renal cell carcinoma (RCC) is the most common solid neoplasm of the adult kidney and has a high potential for developing metastatic spread. Approximately 25-30% of RCC patients have metastatic disease at presentation, and 30-40% of patients develop metastases after the initial diagnosis. Advanced renal cancer is a deadly and difficult-to-treat cancer. The 5-year survival rate of patients with metastatic disease is less than 10%, partly because RCC metastases become resistant to current therapies. Pre-clinical models may help to identify the optimum therapeutic options for individual patients. Here we reviewed various mouse xenograft methods for RCC treatment screening especially patient-derived orthotopic xenograft models. Advantages and disadvantaged of some of the models are also discussed.

The 'Achilles Heel' of Metabolism in Renal Cell Carcinoma: Glutaminase Inhibition as a Rational Treatment Strategy

An important hallmark of cancer is 'metabolic reprogramming' or the rewiring of cellular metabolism to support rapid cell proliferation [1-5]. Metabolic reprogramming through oncometabolite-mediated transformation or activation of oncogenes in renal cell carcinoma (RCC) globally impacts energy production as well as glucose and glutamine utilization in RCC cells, which can promote dependence on glutamine supply to support cell growth and proliferation [6, 7]. Novel inhibitors of glutaminase, a key enzyme in glutamine metabolism, target glutamine addiction as a viable treatment strategy in metastatic RCC (mRCC). Here, we review glutamine metabolic pathways and how changes in cellular glutamine utilization enable the progression of RCC. This overview provides scientific rationale for targeting this pathway in patients with mRCC. We will summarize the current understanding of cellular and molecular mechanisms underlying anti-tumor efficacy of glutaminase inhibitors in RCC, provide an overview of clinical efforts targeting glutaminase in mRCC, and review approaches for identifying biomarkers for patient stratification and detecting therapeutic response early on in patients treated with this novel class of anti-cancer drug. Ultimately, results of ongoing clinical trials will demonstrate whether glutaminase inhibition can be a worthy addition to the current armamentarium of drugs used for patients with mRCC.

Human telomerase reverse transcriptase protein expression predicts tumour aggressiveness and survival in patients with clear cell renal cell carcinoma

Human telomerase reverse transcriptase (hTERT) is an active component of telomerase and responsible for its catalytic activity, associated with cell proliferation and differentiation. For the first time, the present study was conducted to evaluate the expression and prognostic significance of hTERT in different histological subtypes of renal cell carcinoma (RCC). Expression of hTERT was examined in 176 well-defined renal tumour samples including clear cell RCCs (ccRCCs), papillary and chromophobe RCCs using immunohistochemistry on tissue microarrays. The association between hTERT expression and clinicopathological parameters as well as survival outcomes were then analysed. There was a statistically significant difference in terms of hTERT expression among various RCC subtypes. In ccRCC, increased expression of hTERT was significantly associated with advanced stage, higher grade, presence of microvascular invasion, lymph node invasion, and metastasis. Moreover, in the multivariate analysis, tumour stage and tumour size were independent predictors of the disease-specific survival (DSS). Additionally, expression of hTERT was found to be a significant predictor of worse DSS (p = 0.012) in the univariate analysis. In papillary carcinoma samples (type I and II), significant association was detected between hTERT expression and the tumour stage (p = 0.010, p = 0.050), respectively. In chromophobe RCC, no significant association was detected between expression of hTERT and clinicopathological parameters and survival data. We showed that hTERT protein expression was associated with more aggressive tumour behaviour and more advanced disease in ccRCC patients. Also, hTERT may be a novel poor prognostic indicator of DSS, if the patients are followed for more prolonged time periods.

Rituximab (anti-CD20)-modified AZD-2014-encapsulated nanoparticles killing of B lymphoma cells

The mTOR signal pathway is often highly activated in B-cell non-Hodgkin's lymphoma (NHL) and promotes cancer progression and chemo-resistance. Therefore, the pathways of mTOR are an important target for drug development in this disease. In the current study, we developed a rituximab (anti-CD20)-modified mTOR inhibitor, AZD-2014, loaded into nanoparticles (Ab-NPs-AZD-2014) for trial of its anti-NHL effect. In a cultured NHL cell line, Ab-NPs-AZD-2014 inhibited cancer cell growth, induced cell apoptosis, and blocked activation of mTORC1 and mTORC2 in Raji cells. These results indicate that antibody modification and nanomaterial loading of AZD-2014 with anti-CD20 significantly improved efficacy of AZD-2014 against NHL cells. This approach may ultimately deserve testing in therapy against NHL.

mTOR inhibitor INK128 attenuates dextran sodium sulfate-induced colitis by promotion of MDSCs on Treg cell expansion

Accumulating evidence has shown that mammalian target of rapamycin (mTOR) pathway and myeloid-derived suppressor cells (MDSCs) are involved in pathogenesis of inflammatory bowel diseases (IBDs). INK128 is a novel mTOR kinase inhibitor in clinical development. However, the exact roles of MDSCs and INK128 in IBD are unclear. Here, we showed that the INK128 treatment enhanced the resistance of mice to dextran sodium sulfate (DSS)-induced colitis and inhibited the differentiation of MDSCs into macrophages. Moreover, interferon (IFN)-α level was elevated in INK128-treated colitis mice. When stimulated with IFN-α in vitro, MDSCs showed a superior immunosuppression activity. Of note, the regulatory T cells (Tregs) increased but Th1 cells decreased in INK128-treated colitis mice. These results indicate that mTOR inhibitor INK128 attenuates DSS-induced colitis via Treg expansion promoted by MDSCs. Our work provides a new evidence that INK128 is potential to be a therapeutic drug on DSS-induced colitis via regulating MDSCs as well as maintaining Treg expansion.

Co-expression of Cancer Stem Cell Markers OCT4 and NANOG Predicts Poor Prognosis in Renal Cell Carcinomas

Many renal cancer patients experience disease recurrence after combined treatments or immunotherapy due to permanence of cancer stem cells (CSCs). This study was conducted to evaluate the expression patterns and clinical significance of octamer-binding transcription factor 4 (OCT4) and NANOG as the key stem cell factors in renal cell carcinoma (RCC). A total of 186 RCC tissues were immunostained on a tissue microarray (TMA) for the putative CSC markers OCT4 and NANOG. Subsequently, the correlation among the expression of these markers, the clinicopathological variables and survival outcomes were determined. OCT4 and NANOG were expressed in both the nucleus and the cytoplasm of RCC cells. Coexpression of OCT4 and NANOG in renal cancer was significantly associated with RCC subtypes. A significant association was found among nuclear coexpression of OCT4 and NANOG, worse PFS in RCC, and the clear cell renal cell carcinomas (ccRCC) subtype. The OCT4-nuclear ^high/NANOG-nuclear ^high phenotype in RCC and ccRCC subtype indicated aggressive tumor behavior and predicted a worse clinical outcome, which may be a useful biomarker to identify patients at high risk of postoperative recurrence and metastasis. Cytoplasmic expression of NANOG could be considered as a novel independent prognostic predictor in patients with renal cancer.

The TORC1/2 inhibitor TAK228 sensitizes atypical teratoid rhabdoid tumors to cisplatin-induced cytotoxicity

Background

Atypical teratoid/rhabdoid tumors (AT/RTs) are deadly pediatric brain tumors driven by LIN28. Mammalian target of rapamycin (mTOR) is activated in many deadly, drug-resistant cancers and governs important cellular functions such as metabolism and survival. LIN28 regulates mTOR in normal cells. We therefore hypothesized that mTOR is activated downstream of LIN28 in AT/RT, and the brain-penetrating mTOR complex 1 and 2 (mTORC1/2) kinase inhibitor TAK228 would reduce AT/RT tumorigenicity.

Methods

Activation of mTOR in AT/RT was determined by measuring pS6 and pAKT (Ser473) by immunohistochemistry on tissue microarray of 18 primary AT/RT tumors. In vitro growth assays (BrdU and MTS), death assays (CC3, c-PARP by western blot), and survival curves of AT/RT orthotopic xenograft models were used to measure the efficacy of TAK228 alone and in combination with cisplatin.

Results

Lentiviral short hairpin RNA-mediated knockdown of LIN28A led to decreased mTOR activation. Primary human AT/RT had high levels of pS6 and pAKT (Ser473) in 21% and 87% of tumors by immunohistochemistry. TAK228 slowed cell growth, induced apoptosis in vitro, and nearly doubled median survival of orthotopic xenograft models of AT/RT. TAK228 combined with cisplatin synergistically slowed cell growth and enhanced cisplatin-induced apoptosis. Suppression of AKT sensitized cells to cisplatin-induced apoptosis and forced activation of AKT protected cells. Combined treatment with TAK228 and cisplatin significantly extended survival of orthotopic xenograft models of AT/RT compared with each drug alone.

Conclusions

TAK228 has efficacy in AT/RT as a single agent and synergizes with conventional chemotherapies by sensitizing tumors to cisplatin-induced apoptosis. These results suggest TAK228 may be an effective new treatment for AT/RT.

CD44 positive and sorafenib insensitive hepatocellular carcinomas respond to the ATP-competitive mTOR inhibitor INK128

The mTOR pathway is activated in about 50% of patients with hepatocellular carcinoma (HCC). In an effort to identify new pathways and compounds to treat advanced HCC, we considered the ATP-competitive mTOR inhibitor INK128. ATP-competitive mTOR inhibitors attenuate both mTORC1 and mTORC2. INK128 was evaluated in sorafenib sensitive and insensitive HCC cell lines, CD44low and CD44high HCC and those cell lines with acquired sorafenib resistance. CD44 was significantly increased in Huh7 cells made resistant to sorafenib. Forced expression of CD44 enhanced cellular proliferation and migration, and rendered the cells more sensitive to the anti-proliferative effects of INK128. INK128 suppressed CD44 expression in HCC cells while allosteric mTOR inhibitors did not. CD44 inhibition correlated with 4EBP1 phosphorylation status. INK128 showed better anti-proliferative and anti-migration effects on the mesenchymal-like HCC cells, CD44high HCC cells compared to the allosteric mTOR inhibitor everolimus. Moreover, a combination of INK128 and sorafenib showed improved anti-proliferative effects in CD44high HCC cells. INK128 was efficacious at reducing tumor growth in CD44high SK-Hep1 xenografts in mice when given as monotherapy or in combination with sorafenib. Since the clinical response to sorafenib is highly variable, our findings suggest that ATP-competitive mTOR inhibitors may be effective in treating advanced, CD44-expressing HCC patients who are insensitive to sorafenib.

Use of dual mTOR inhibitor MLN0128 against everolimus-resistant breast cancer

PURPOSE

HR+/HER2- aromatase inhibitor-resistant metastatic breast cancer can be treated with everolimus and a second AI until the cancer recurs. Targeting these everolimus-resistant patients with the latest standard of care, CDK4/6 inhibitors, has not been clearly addressed. Understanding the signaling transduction pathways, which everolimus resistance activates, will elucidate the mechanisms and offer treatment strategies of everolimus resistance.

METHODS

To mimic the clinical setting, letrozole-resistant cells were used to generate an everolimus-resistant model (RAD-R). Reverse phase protein array (RPPA) was performed to reveal changes in the signaling transduction pathways, and expression levels of key proteins were analyzed. Inhibitors targeting the major signaling pathways, a CDK4/6 inhibitor palbociclib and a mTORC1/2 inhibitor (MLN0128), were evaluated to establish resistance mechanisms of RAD-R.

RESULTS

RPPA results from RAD-R indicated changes to significant regulatory pathways and upregulation of p-AKT expression level associating with everolimus resistance. MLN0128, that inhibits the AKT phosphorylation, effectively suppressed the proliferation of RAD-R cells while treatment with palbociclib had no effect.

CONCLUSION

Among the many signaling transduction pathways, which are altered post everolimus resistance, targeting dual mTORC1/2 is a possible option for patients who have recurrent disease from previous everolimus treatment.

Cancer stem cell markers predict a poor prognosis in renal cell carcinoma: a meta-analysis

Background

Relevant markers of CSCs may serve as prognostic biomarkers of RCC. However, their actual prognostic significance remains inconclusive. Thus, a meta-analysis was performed to reevaluate the association of CSCs-relevant markers (CXCR4, CD133, CD44, CD105) expression with RCC prognosis more precisely.

Methods

PubMed and Embase were searched to look for eligible studies. The pooled hazard ratios (HR) with 95% confidence intervals (95% CI) were used to reassess the association of CSCs markers expression and RCC prognosis of overall survival (OS), cancer-specific survival (CSS), disease-free survival (DFS), and progression-free survival (PFS).

Results

There were 25 relevant articles, encompassing 2673 RCC patients, eligible for meta-analysis. Overall pooled analysis suggested that high CSCs markers expression predicted poor OS (HR, 2.10, 95% CI: 1.73–2.55) and DFS (HR, 3.77, 95% CI: 2.30–6.19). High CXCR4 expression predicted worse OS (HR, 2.57, 95% CI: 1.95–3.40), CSS (HR,1.97, 95% CI: 1.50–2.59), and DFS (HR, 5.82, 95% CI: 3.01–11.25). CD44 over-expression correlated with a poor OS(HR,1.58, 95% CI: 1.14–2.18), CSS (HR, 2.58, 95% CI: 1.27–5.23), and DFS (HR, 4.49, 95% CI: 2.12–9.53) in RCC patients. CD133 was an independent favorable prognostic factor for CSS (HR, 0.4, 95% CI: 0.29–0.54).

Conclusions

The presence of CSCs markers correlates with poor RCC outcome. CSCs may be potentially utilized as prognostic markers to stratify RCC patients, probably representing also a novel potential therapeutic target.

MLN0128, a novel mTOR kinase inhibitor, disrupts survival signaling and triggers apoptosis in AML and AML stem/ progenitor cells

mTOR activation leads to enhanced survival signaling in acute myeloid leukemia (AML) cells. The active-site mTOR inhibitors (asTORi) represent a promising new approach to targeting mTOR in AKT/mTOR signaling. MLN0128 is an orally-administered, second-generation asTORi, currently in clinical development. We examined the anti-leukemic effects and the mechanisms of action of MLN0128 in AML cell lines and primary samples, with a particular focus on its effect in AML stem/progenitor cells. MLN0128 inhibited cell proliferation and induced apoptosis in AML by attenuating the activity of mTOR complex 1 and 2. Using time-of-flight mass cytometry, we demonstrated that MLN0128 selectively targeted and functionally inhibited AML stem/progenitor cells with high AKT/mTOR signaling activity. Using the reverse-phase protein array technique, we measured expression and phosphorylation changes in response to MLN0128 in 151 proteins from 24 primary AML samples and identified several pro-survival pathways that antagonize MLN0128-induced cellular stress. A combined blockade of AKT/mTOR signaling and these pro-survival pathways facilitated AML cell killing. Our findings provide a rationale for the clinical use of MLN0128 to target AML and AML stem/progenitor cells, and support the use of combinatorial multi-targeted approaches in AML therapy.

Pan-mTOR inhibitor MLN0128 is effective against intrahepatic cholangiocarcinoma in mice

BACKGROUND & AIMS

Intrahepatic cholangiocarcinoma (ICC) is a lethal malignancy without effective treatment options. MLN0128, a second generation pan-mTOR inhibitor, shows efficacy for multiple tumor types. We evaluated the therapeutic potential of MLN0128 vs. gemcitabine/oxaliplatin in a novel ICC mouse model.

METHODS

We established a novel ICC mouse model via hydrodynamic transfection of activated forms of AKT (myr-AKT) and Yap (YapS127A) protooncogenes (that will be referred to as AKT/YapS127A). Genetic approaches were applied to study the requirement of mTORC1 and mTORC2 in mediating AKT/YapS127A driven tumorigenesis. Gemcitabine/oxaliplatin and MLN0128 were administered in AKT/YapS127A tumor-bearing mice to study their anti-tumor efficacy in vivo. Multiple human ICC cell lines were used for in vitro experiments. Hematoxylin and eosin staining, immunohistochemistry and immunoblotting were applied for the characterization and mechanistic study.

RESULTS

Co-expression of myr-AKT and YapS127A promoted ICC development in mice. Both mTORC1 and mTORC2 complexes were required for AKT/YapS127A ICC development. Gemcitabine/oxaliplatin had limited efficacy in treating late stage AKT/YapS127A ICC. In contrast, partial tumor regression was achieved when MLN0128 was applied in the late stage of AKT/YapS127A cholangiocarcinogenesis. Furthermore, when MLN0128 was administered in the early stage of AKT/YapS127A carcinogenesis, it led to disease stabilization. Mechanistically, MLN0128 efficiently inhibited AKT/mTOR signaling both in vivo and in vitro, inducing strong ICC cell apoptosis and only marginally affecting proliferation.

CONCLUSIONS

This study suggests that mTOR kinase inhibitors may be beneficial for the treatment of ICC, even in tumors that are resistant to standard of care chemotherapeutics, such as gemcitabine/oxaliplatin-based regimens, especially in the subset of tumors exhibiting activated AKT/mTOR cascade. Lay summary: We established a novel mouse model of intrahepatic cholangiocarcinoma (ICC). Using this new preclinical model, we evaluated the therapeutic potential of mTOR inhibitor MLN0128 vs. gemcitabine/oxaliplatin (the standard chemotherapy for ICC treatment). Our study shows the anti-neoplastic potential of MLN0128, suggesting that it may be superior to gemcitabine/oxaliplatin-based chemotherapy for the treatment of ICC, especially in the tumors exhibiting activated AKT/mTOR cascade.

mTOR Inhibitors in Castration-Resistant Prostate Cancer: A Systematic Review

BACKGROUND

The progression of prostate cancer to castration-resistant prostate cancer (CRPC) is often a result of somatic alterations in the PI3K/Akt/mTOR (mammalian target of rapamycin) pathway, suggesting that therapies targeting this pathway might lead to improved survival and efficacy. Here, we systematically evaluate the results of clinical trials investigating mTOR inhibition in CRPC and utilize preclinical data to predict clinical outcomes.

METHODS

Trials included in the study were identified through PubMed and via review of conference abstracts cited by relevant review articles. The eligibility of trials was independent of sample size, clinical setting, or date.

RESULTS

A total of 14 studies were eligible for qualitative analysis. The clinical setting was variable among studies, and all utilized an allosteric mTOR inhibitor as either a monotherapy or in combination. Molecular criteria were evaluated in three trials. Among most studies, the prostate-specific antigen level declined during treatment, but often increased shortly thereafter. Partial responses to treatment were minimal, and no complete responses were reported. Two studies exploring therapy with an mTOR inhibitor in combination with bicalutamide resulted in minimal efficacy. Overall, allosteric mTOR inhibition was deemed to be inadequate for the treatment of CRPC.

CONCLUSION

Preclinical data suggest that a reciprocal feedback mechanism between PI3K and androgen receptor signaling is a potential mechanism behind the clinical inefficacy of mTOR inhibitors in CRPC, indicating combinatorial targeting of PI3K, mTORC1/2, and the androgen receptor might be more effective. Comprehensive analysis of preclinical data to assess clinical trial targets and efficacy may reduce the number of unproductive trials and identify potentially beneficial combinatorial therapies for resistant disease.

Dual mTOR Kinase Inhibitor MLN0128 Sensitizes HR+/HER2+ Breast Cancer Patient-Derived Xenografts to Trastuzumab or Fulvestrant

Purpose: Therapeutic strategies against hormonal receptor-positive (HR⁺)/HER2⁺ breast cancers with poor response to trastuzumab need to be optimized.Experimental Design: Two HR⁺/HER2⁺ patient-derived xenograft (PDX) models named as COH-SC1 and COH-SC31 were established to explore targeted therapies for HER2⁺ breast cancers. RNA sequencing and RPPA (reverse phase protein array) analyses were conducted to decipher molecular features of the two PDXs and define the therapeutic strategy of interest, validated by in vivo drug efficacy examination and in vitro cell proliferation analysis.Results: Estrogen acted as a growth driver of trastuzumab-resistant COH-SC31 tumors but an accelerator in the trastuzumab-sensitive COH-SC1 model. In vivo trastuzumab efficacy examination further confirmed the consistent responses between PDXs and the corresponding tumors. Integrative omics analysis revealed that mammalian target of rapamycin (mTOR) and ERα signaling predominantly regulate tumor growth of the two HR⁺/HER2⁺ PDXs. Combination of the dual mTOR complex inhibitor MLN0128 and anti-HER2 trastuzumab strongly suppressed tumor growth of COH-SC1 PDX accompanied by increasing ER-positive cell population in vivo Instead, MLN0128 in combination with antiestrogen fulvestrant significantly halted the growth of HR⁺/HER2⁺ cancer cells in vitro and trastuzumab-resistant COH-SC31 as well as trastuzumab-sensitive COH-SC1 tumors in vivoConclusions: Compared with the standard trastuzumab treatment, this study demonstrates alternative therapeutic strategies against HR⁺/HER2⁺ tumors through establishment of two PDXs coupled with integrative omics analyses and in vivo drug efficacy examination. This work presents a prototype of future "co-clinical" trials to tailor personalized medicine in clinical practice. Clin Cancer Res; 24(2); 395-406. ©2017 AACR.

Experimental imaging in orthotopic renal cell carcinoma xenograft models: comparative evaluation of high-resolution 3D ultrasonography, in-vivo micro-CT and 9.4T MRI

In this study, we aimed to comparatively evaluate high-resolution 3D ultrasonography (hrUS), in-vivo micro-CT (μCT) and 9.4T MRI for the monitoring of tumor growth in an orthotopic renal cell carcinoma (RCC) xenograft model since there is a lack of validated, non-invasive imaging tools for this purpose. 1 × 10⁶ Caki-2 RCC cells were implanted under the renal capsule of 16 immunodeficient mice. Local and systemic tumor growth were monitored by regular hrUS, μCT and MRI examinations. Cells engrafted in all mice and gave rise to exponentially growing, solid tumors. All imaging techniques allowed to detect orthotopic tumors and to precisely calculate their volumes. While tumors appeared homogenously radiolucent in μCT, hrUS and MRI allowed for a better visualization of intratumoral structures and surrounding soft tissue. Examination time was the shortest for hrUS, followed by μCT and MRI. Tumor volumes determined by hrUS, μCT and MRI showed a very good correlation with each other and with caliper measurements at autopsy. 10 animals developed pulmonary metastases being well detectable by μCT and MRI. In conclusion, each technique has specific strengths and weaknesses, so the one(s) best suitable for a specific experiment may be chosen individually.

Cytoplasmic expression of CD133 stemness marker is associated with tumor aggressiveness in clear cell renal cell carcinoma

Prominin-1 (CD133) is one of the most commonly used markers for cancer stem cells (CSCs), which are characterized by their ability for self-renewal and tumorigenicity. However, the clinical and prognostic significance of CSCs in renal cell carcinoma (RCC) remains unclear. The aim of this study was to investigate the expression patterns and prognostic significance of the cancer stem cell marker CD133 in different histological subtypes of RCC. CD133 expression was evaluated using immunohistochemistry in 193 well-defined renal tumor samples on tissue microarrays, including 136 (70.5%) clear cell renal cell carcinomas (CCRCCs), 26 (13.5%) papillary RCCs, and 31 (16.1%) chromophobe RCCs. The association between CD133 expression and clinicopathological features as well as the survival outcomes was determined. There was a statistically significant difference between CD133 expression among the different RCC subtypes. In CCRCC, higher cytoplasmic expression of CD133 was significantly associated with increase in grade, stage, microvascular invasion (MVI) and lymph node invasion (LNI), while no association was found with the membranous expression. Moreover, on multivariate analysis, TNM stage and nuclear grade were independent prognostic factors for overall survival (OS) in cytoplasmic expression. We showed that higher cytoplasmic CD133 expression was associated with more aggressive tumor behavior and more advanced disease in CCRCC but not in the other examined subtypes. Our results demonstrated that higher cytoplasmic CD133 expression is clinically significant in CCRCC and is associated with increased tumor aggressiveness and is useful for predicting cancer progression.

TAK-228 (formerly MLN0128), an investigational dual TORC1/2 inhibitor plus paclitaxel, with/without trastuzumab, in patients with advanced solid malignancies

PURPOSE

This phase I trial evaluated the safety, pharmacokinetic profile, and antitumor activity of investigational oral TORC1/2 inhibitor TAK-228 plus paclitaxel, with/without trastuzumab, in patients with advanced solid malignancies.

METHODS

Sixty-seven patients received TAK-228 6-40 mg via three dosing schedules; once daily for 3 days (QDx3d QW) or 5 days per week (QDx5d QW), and once weekly (QW) plus paclitaxel 80 mg/m² (dose-escalation phase, n = 47) and with/without trastuzumab 2 mg/kg (expansion phase, n = 20). Doses were escalated using a modified 3 + 3 design, based upon dose-limiting toxicities in cycle 1.

RESULTS

TAK-228 pharmacokinetics exhibited dose-dependent increase in exposure when dosed with paclitaxel and no apparent differences when administered with or 24 h after paclitaxel. Dose-limiting toxicities were dehydration, diarrhea, stomatitis, fatigue, rash, thrombocytopenia, neutropenia, leukopenia, and nausea. The maximum tolerated dose of TAK-228 was determined as 10-mg QDx3d QW; the expansion phase proceeded with 8-mg QDx3d QW. Overall, the most common grade ≥3 drug-related toxicities were neutropenia (21%), diarrhea (12%), and hyperglycemia (12%). Of 54 response-evaluable patients, eight achieved partial response and six had stable disease lasting ≥6 months.

CONCLUSION

TAK-228 demonstrated a safety profile consistent with other TORC inhibitors and promising preliminary antitumor activity in a range of tumor types; no meaningful difference was noted in the pharmacokinetics of TAK-228 when administered with or 24 h after paclitaxel. These findings support further investigation of TAK-228 in combination with other agents including paclitaxel, with/without trastuzumab, in patients with advanced solid tumors. CLINICALTRIALS.

GOV IDENTIFIER

NCT01351350.

Dual mTOR inhibitor MLN0128 suppresses Merkel cell carcinoma (MCC) xenograft tumor growth

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer. Pathologic activation of PI3K/mTOR pathway and elevated expression of c-Myc are frequently detected in MCC. Yet, there is no targeted therapy presently available for this lethal disease. Recently, MLN0128, a second-generation dual TORC1/2 inhibitor is shown to have therapeutic efficacy in preclinical studies. MLN0128 is currently in clinical trials as a potential therapy for advanced cancers. Here we characterize the therapeutic efficacy of MLN0128 in the preclinical setting of MCC and delineate downstream targets of mTORC1/2 in MCC cellular systems. MLN0128 significantly attenuates xenograft MCC tumor growth independent of Merkel cell polyomavirus. Moreover, MLN0128 markedly diminishes MCC cell proliferation and induces apoptosis. Further investigations indicate that senescence does not contribute to MLN0128-mediated repression of xenograft MCC tumor growth. Finally, we also observe robust antitumor effects of MLN0128 when administered as a dual therapy with JQ1, a bromodomain protein BRD4 inhibitor. These results suggest dual blockade of PI3K/mTOR pathway and c-Myc axis is effective in the control of MCC tumor growth. Our results demonstrate that MLN0128 is potent as monotherapy or as a member of combination therapy with JQ1 for advanced MCC.

Determination of MLN0128, an investigational antineoplastic agent, in human plasma by LC-MS/MS

MLN0128, an mTOR kinase inhibitor, is currently undergoing clinical investigation for treatment of a variety of cancers. To support this work, an LC-MS/MS method has been developed for the determination of MLN0128 in human plasma. A structural analog STK040263 was used as the internal standard. Both MLN0128 and the IS were first extracted from plasma using methyl tert-butyl ether; then separated on a Waters XTerra® MS C₁₈ column using a mobile phase consisting of methanol-acetonitrile-10.0 mm ammonium formate (34:6:60, v/v/v) at a flow rate of 0.300 mL min^-1 . Quantitation of MLN0128 was done by positive electrospray ionization tandem mass spectrometry in multiple-reaction-monitoring mode. This method has a total run time of <4 min with the retention times of 1.95 and 2.94 min for the IS and MLN0128, respectively. The method has been validated per the US Food and Drug Administration guidance for bioanalytical method validation. It has a calibration range of 0.100-50.0 ng mL^-1 in human plasma with a correlation coefficient > 0.999. The overall assay accuracy and precision were ≤ ± 4 and ≤8%, respectively. The IS normalized recovery of MLN0128 was 98-100%. The stability studies showed that MLN0128 was stable under all tested conditions. The method developed may be useful for clinical studies of MLN0128.

Cabozantinib inhibits tumor growth and metastasis of a patient-derived xenograft model of papillary renal cell carcinoma with MET mutation

MET plays an important role in the development and progression of papillary renal cell carcinoma (pRCC). Evaluation of efficacy of MET inhibitors against pRCC has been hampered by limited preclinical models depicting MET abnormalities. We established a new patient-derived xenograft (PDX) model of pRCC carrying an activating mutation of MET and tested the ability of cabozantinib, an inhibitor of receptor tyrosine kinases including MET, to inhibit tumor growth and metastasis. Precision-cut, thin tissue slices from a pRCC specimen obtained by nephrectomy were implanted under the renal capsule of RAG2^-/-γC^-/- mice to establish first generation TSG-RCC-030. Histologic and genetic fidelity and metastatic potential of this model were characterized by immunohistochemistry, direct DNA sequencing and quantitative polymerase chain reaction (qPCR). The effect of cabozantinib on tumor growth and metastasis was evaluated. Whether measurements of circulating tumor DNA (ctDNA) by allele-specific qPCR could be used as a biomarker of tumor growth and response to therapy was determined. Subrenal and subcutaneous tumor grafts showed high take rates and metastasized to the lung. Both primary tumors and metastases expressed typical markers of pRCC and carried the same activating MET mutation as the parental tumor. Cabozantinib treatment caused striking tumor regression and inhibited lung metastasis in TSG-RCC-030. Plasma ctDNA levels correlated with tumor volume in control mice and changed in response to cabozantinib treatment. TSG-RCC-030 provides a realistic preclinical model to better understand the development and progression of pRCC with MET mutation and accelerate the development of new therapies for pRCC.

Catalytic mTOR inhibitors can overcome intrinsic and acquired resistance to allosteric mTOR inhibitors

We tested the antitumor efficacy of mTOR catalytic site inhibitor MLN0128 in models with intrinsic or acquired rapamycin-resistance. Cell lines that were intrinsically rapamycin-resistant as well as those that were intrinsically rapamycinsensitive were sensitive to MLN0128 in vitro. MLN0128 inhibited both mTORC1 and mTORC2 signaling, with more robust inhibition of downstream 4E-BP1 phosphorylation and cap-dependent translation compared to rapamycin in vitro. Rapamycin-sensitive BT474 cell line acquired rapamycin resistance (BT474 RR) with prolonged rapamycin treatment in vitro. This cell line acquired an mTOR mutation (S2035F) in the FKBP12-rapamycin binding domain; mTORC1 signaling was not inhibited by rapalogs but was inhibited by MLN0128. In BT474 RR cells, MLN0128 had significantly higher growth inhibition compared to rapamycin in vitro and in vivo. Our results demonstrate that MLN0128 may be effective in tumors with intrinsic as well as acquired rapalog resistance. mTOR mutations are a mechanism of acquired resistance in vitro; the clinical relevance of this observation needs to be further evaluated.

Distinct inhibitory effects on mTOR signaling by ethanol and INK128 in diffuse large B-cell lymphoma

BACKGROUND

The mechanistic target of rapamycin, (mTOR) kinase plays a pivotal role in controlling critical cellular growth and survival pathways, and its aberrant induction is implicated in cancer pathogenesis. Therefore, suppression of active mTOR signaling has been of great interest to researchers; several mTOR inhibitors have been discovered to date. Ethanol (EtOH), similar to pharmacologic mTOR inhibitors, has been shown to suppress the mTOR signaling pathway, though in a non-catalytic manner. Despite population studies showing that the consumption of EtOH has a protective effect against hematological malignancies, the mechanisms behind EtOH's modulation of mTOR activity in cells and its downstream consequences are largely unknown. Here we evaluated the effects of EtOH on the mTOR pathway, in comparison to the active-site mTOR inhibitor INK128, and compared translatome analysis of their downstream effects in diffuse large B-cell lymphoma (DLBCL).

RESULTS

Treatment of DLBCL cells with EtOH suppressed mTORC1 complex formation while increasing AKT phosphorylation and mTORC2 complex assembly. INK128 completely abrogated AKT phosphorylation without affecting the structure of mTORC1/2 complexes. Accordingly, EtOH less profoundly suppressed cap-dependent translation and global protein synthesis, compared to a remarkable inhibitory effect of INK128 treatment. Importantly, EtOH treatment induced the formation of stress granules, while INK128 suppressed their formation. Microarray analysis of polysomal RNA revealed that although both agents primarily affected cell growth and survival, EtOH and INK128 regulated the synthesis of mostly distinct genes involved in these processes. Though both EtOH and INK128 inhibited cell cycle, proliferation and autophagy, EtOH, in contrast to INK128, did not induce cell apoptosis.

CONCLUSION

Given that EtOH, similar to pharmacologic mTOR inhibitors, inhibits mTOR signaling, we systematically explored the effect of EtOH and INK128 on mTOR signal transduction, components of the mTORC1/2 interaction and their downstream effectors in DLBCL malignancy. We found that EtOH partially inhibits mTOR signaling and protein translation, compared to INK128's complete mTOR inhibition. Translatome analysis of mTOR downstream target genes established that differential inhibition of mTOR by EtOH and INK128 distinctly modulates translation of specific subsets of mRNAs involved in cell growth and survival, leading to differential cellular response and survival.

MLN0128, an ATP-competitive mTOR kinase inhibitor with potent in vitro and in vivo antitumor activity, as potential therapy for bone and soft-tissue sarcoma

The mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase that exists in two complexes (mTORC1 and mTORC2) and integrates extracellular and intracellular signals to act as a master regulator of cell growth, survival, and metabolism. The PI3K/AKT/mTOR prosurvival pathway is often dysregulated in multiple sarcoma subtypes. First-generation allosteric inhibitors of mTORC1 (rapalogues) have been extensively tested with great preclinical promise, but have had limited clinical utility. Here, we report that MLN0128, a second-generation, ATP-competitive, pan-mTOR kinase inhibitor, acts on both mTORC1 and mTORC2 and has potent in vitro and in vivo antitumor activity in multiple sarcoma subtypes. In vitro, MLN0128 inhibits mTORC1/2 targets in a concentration-dependent fashion and shows striking antiproliferative effect in rhabdomyosarcoma (RMS), Ewing sarcoma, malignant peripheral nerve sheath tumor, synovial sarcoma, osteosarcoma, and liposarcoma. Unlike rapamycin, MLN0128 inhibits phosphorylation of 4EBP1 and NDRG1 as well as prevents the reactivation of pAKT that occurs via negative feedback release with mTORC1 inhibition alone. In xenograft models, MLN0128 treatment results in suppression of tumor growth with two dosing schedules (1 mg/kg daily and 3 mg/kg b.i.d. t.i.w.). At the 3 mg/kg dosing schedule, MLN0128 treatment results in significantly better tumor growth suppression than rapamycin in RMS and Ewing sarcoma models. In addition, MLN0128 induces apoptosis in models of RMS both in vitro and in vivo. Results from our study strongly suggest that MLN0128 treatment should be explored further as potential therapy for sarcoma.

mTOR signaling in tumorigenesis

mTOR (the mechanistic target of rapamycin) is an atypical serine/threonine kinase involved in regulating major cellular functions including growth and proliferation. Deregulation of the mTOR signaling pathway is one of the most commonly observed pathological alterations in human cancers. To this end, oncogenic activation of the mTOR signaling pathway contributes to cancer cell growth, proliferation and survival, highlighting the potential for targeting the oncogenic mTOR pathway members as an effective anti-cancer strategy. In order to do so, a thorough understanding of the physiological roles of key mTOR signaling pathway components and upstream regulators would guide future targeted therapies. Thus, in this review, we summarize available genetic mouse models for mTORC1 and mTORC2 components, as well as characterized mTOR upstream regulators and downstream targets, and assign a potential oncogenic or tumor suppressive role for each evaluated molecule. Together, our work will not only facilitate the current understanding of mTOR biology and possible future research directions, but more importantly, provide a molecular basis for targeted therapies aiming at key oncogenic members along the mTOR signaling pathway.

Development of a realistic in vivo bone metastasis model of human renal cell carcinoma

About one-third of patients with advanced renal cell carcinoma (RCC) have bone metastases. The incidence of RCC is increasing and bone metastatic RCC merits greater focus. Realistic preclinical bone metastasis models of RCC are lacking, hampering the development of effective therapies. We developed a realistic in vivo bone metastasis model of human RCC by implanting precision-cut tissue slices under the renal capsule of immunodeficient mice. The presence of disseminated cells in bone marrow of tissue slice graft (TSG)-bearing mice was screened by human-specific polymerase chain reaction and confirmed by immunohistology using human-specific antibody. Disseminated tumor cells in bone marrow of TSG-bearing mice derived from three of seven RCC patients were detected as early as 1 month after tissue implantation at a high frequency with close resemblance to parent tumors (e.g., CAIX expression and high vascularity). The metastatic patterns of TSGs correlated with disease progression in patients. In addition, TSGs retained capacity to metastasize to bone at high frequency after serial passaging and cryopreservation. Moreover, bone metastases in mice responded to Temsirolimus treatment. Intratibial injections of single cells generated from TSGs showed 100 % engraftment and produced X-ray-visible tumors as early as 3 weeks after cancer cell inoculation. Micro-computed tomography (μCT) and histological analysis revealed osteolytic characteristics of these lesions. Our results demonstrated that orthotopic RCC TSGs have potential to develop bone metastases that respond to standard therapy. This first reported primary RCC bone metastasis model provides a realistic setting to test therapeutics to prevent or treat bone metastases in RCC.