Combination of mTORC1/2 inhibitor vistusertib plus fulvestrant in vitro and in vivo targets oestrogen receptor-positive endocrine-resistant breast cancer

Abstract Background Endocrine therapies are still the main strategy for the treatment of oestrogen receptor-positive (ER+) breast cancers (BC), but resistance remains problematic. Cross-talk between ER and PI3K/AKT/mTORC has been associated with ligand-independent transcription of ER. We have previously reported the anti-proliferative effects of the combination of everolimus (an mTORC1 inhibitor) with endocrine therapy in resistance models, but potential routes of escape via AKT signalling can lead to resistance; therefore, the use of dual mTORC1/2 inhibitors has met with significant interest. Methods To address this, we tested the effect of vistusertib, a dual mTORC1 and mTORC2 inhibitor, in a panel of endocrine-resistant and endocrine-sensitive ER+ BC cell lines, with varying PTEN, PIK3CA and ESR1 mutation status. End-points included proliferation, cell signalling, cell cycle and effect on ER-mediated transcription. Two patient-derived xenografts (PDX) modelling endocrine resistance were used to assess the efficacy of vistusertib, fulvestrant or the combination on tumour progression, and biomarker studies were conducted using immunohistochemistry and RNA-seq technologies. Results Vistusertib caused a dose-dependent decrease in proliferation of all the cell lines tested and reduced abundance of mTORC1, mTORC2 and cell cycle markers, but caused an increase in abundance of EGFR, IGF1R and ERBB3 in a context-dependent manner. ER-mediated transcription showed minimal effect of vistusertib. Combined therapy of vistusertib with fulvestrant showed synergy in two ER+ PDX models of resistance to endocrine therapy and delayed tumour progression after cessation of therapy. Conclusions These data support the notion that models of acquired endocrine resistance may have a different sensitivity to mTOR inhibitor/endocrine therapy combinations.

Download Full-text

Vorinostat (SAHA) Inhibits STAT6 Phosphorylation and Transcription, Downregulates Bcl-xL, and Induces Apoptosis in Hodgkin Lymphoma (HL) Cell Lines.

Blood ◽

10.1182/blood.v110.11.380.380 ◽

2007 ◽

Vol 110 (11) ◽

pp. 380-380 ◽

Cited By ~ 2

Author(s):

Daniela Buglio ◽

Georgios Georgakis ◽

Kazuhiko Arima ◽

Yong-Jun Liu ◽

Anas Younes

Keyword(s):

Cell Cycle ◽

T Cells ◽

B Cell ◽

Hodgkin Lymphoma ◽

Cell Lines ◽

Regulatory Protein ◽

Epigenetic Mechanism ◽

Dependent Manner

Abstract Vorinostat (SAHA) Inhibits STAT6 Phosphorylation and Transcription, Downregulates Bcl-xL, and Induces Apoptosis in Hodgkin Lymphoma (HL) Cell Lines. Although the malignant Hodgkin and Reed Sternberg (HRS) cells of HL are of B-cell origin, they infrequently express B-cell antigens. Recent studies demonstrated that several B-cell specific genes are silenced in HRS cells by epigenetic mechanism, suggesting that this process may be reversible and could be explored therapeutically with deacetylase (DAC) inhibitors or hypomethylating agents. Pan-DAC and isotype-selective DAC inhibitors have shown promising activity in vitro and in vivo in a variety of lymphoid malignancies, including HL. However, the mechanisms of antiproliferative action of DAC inhibitors in HL remain unknown. In this study, we examined the antiproliferative effects of the pan-DAC inhibitor vorinostat (inhibits class I and class II DACs) on HL cell lines and determined its effect on signaling mechanisms that are known to promote HRS cell survival, including STAT3, STAT6, Akt, and ERK pathways. Vorinostat inhibited DACs as evident by the increase in histone-3 acetylation as early as 30 minutes of incubation. Furthermore, vorinostat induced the expression of the cell cycle regulatory protein p21 which was associated with an early increase in the G2M cell cycle fraction in HL cells. Vorinostat had no inhibitory effect on SATA3 or ERK, but inhibited STAT6 phosphorylation and transcription in a dose and time dependant manner. This effect was associated with a decrease in Akt phosphorylation on Ser473 residue. Because STAT6 has been reported to transcriptionally regulate Bcl-XL and Thymus and activation-regulated chemokines (TARC), we examined the effect of vorinostat on these two targets in HL cells. TARC has been shown to play an important role in attracting Th2-type T cells and T-regulatory (T-reg) cells, and to be elevated in sera from patients with HL. Vorinostat downregulated the mRNA expression of TARC in a dose dependent manner, suggesting that it may have a role in regulating chemotaxis of reactive T cells and T-reg cells to HL microenvironment in vivo. Moreover, vorinostat reduced the cellular level of the antiapoptotic protein Bcl-xL which was associated with activation of the caspase pathway, and induction of apoptosis in HL cells. Collectively, these data suggest that DAC inhibition in HL by vorinostat may induce cell death by inhibiting STAT6 and downregulating its antiapoptotic target bcl-xL protein. Furthermore, our data suggest that DAC inhibition may have an added effect in vivo on the cellular component in HL microenvironment by inhibiting TARC.

Download Full-text

Piperlongumine, a Potent Anticancer Phytotherapeutic, Induces Cell Cycle Arrest and Apoptosis In Vitro and In Vivo through the ROS/Akt Pathway in Human Thyroid Cancer Cells

Cancers ◽

10.3390/cancers13174266 ◽

2021 ◽

Vol 13 (17) ◽

pp. 4266

Author(s):

Fang-Ping Kung ◽

Yun-Ping Lim ◽

Wen-Ying Chao ◽

Yi-Sheng Zhang ◽

Hui-I Yu ◽

...

Keyword(s):

Cell Cycle ◽

Thyroid Cancer ◽

Cancer Cells ◽

Cell Lines ◽

Human Thyroid ◽

Akt Pathway ◽

Dependent Manner ◽

Apoptosis Pathway

Thyroid cancer (TC) is the most common endocrine malignancy, and its global incidence has steadily increased over the past 15 years. TC is broadly divided into well-differentiated, poorly differentiated, and undifferentiated types, depending on the histological and clinical parameters. Thus far, there are no effective treatments for undifferentiated thyroid cancers or advanced and recurrent cancer. Therefore, the development of an effective therapeutic is urgently needed for such patients. Piperlongumine (PL) is a naturally occurring small molecule derived from long pepper; it is selectively toxic to cancer cells by generating reactive oxygen species (ROS). In this study, we demonstrate the potential anticancer activity of PL in four TC cell lines. For this purpose, we cultured TC cell lines and analyzed the following parameters: Cell viability, colony formation, cell cycle, apoptosis, and cellular ROS induction. PL modulated the cell cycle, induced apoptosis, and suppressed tumorigenesis in TC cell lines in a dose- and time-dependent manner through ROS induction. Meanwhile, an intrinsic caspase-dependent apoptosis pathway was observed in the TC cells under PL treatment. The activation of Erk and the suppression of the Akt/mTOR pathways through ROS induction were seen in cells treated with PL. PL-mediated apoptosis in TC cells was through the ROS-Akt pathway. Finally, the anticancer effect and safety of PL were also demonstrated in vivo. Our findings indicate that PL exhibits antitumor activity and has the potential for use as a chemotherapeutic agent against TC. This is the first study to show the sensitivity of TC cell lines to PL.

Download Full-text

MDM2 Inhibition in Combination with Endocrine Therapy and CDK4/6 Inhibition for the Treatment of ER-Positive Breast Cancer

10.1101/2020.06.09.140921 ◽

2020 ◽

Author(s):

Neil Portman ◽

Heloisa H. Milioli ◽

Sarah Alexandrou ◽

Rhiannon Coulson ◽

Aliza Yong ◽

...

Keyword(s):

Breast Cancer ◽

Cell Cycle ◽

Endocrine Therapy ◽

Cell Lines ◽

Patient Derived Xenograft ◽

Er Positive ◽

Mcf 7 ◽

Positive Breast Cancer

AbstractBackgroundResistance to endocrine therapy is a major clinical challenge in the management of estrogen receptor (ER)-positive breast cancer. In this setting p53 is frequently wildtype and its activity may be suppressed via upregulation of its key regulator MDM2. This underlies our rationale to evaluate MDM2 inhibition as a therapeutic strategy in treatment resistant ER-positive breast cancer.MethodsWe used the MDM2 inhibitor NVP-CGM097 to treat in vitro and in vivo models alone and in combination with fulvestrant or palbociclib. We perform cell viability, cell cycle, apoptosis and senescence assays to evaluate antitumor effects in p53 wildtype and p53 mutant ER positive cell lines (MCF-7, ZR75-1, T-47D) and MCF-7 lines resistant to endocrine therapy and to CDK4/6 inhibition. We further assess the drug effects in patient-derived xenograft (PDX) models of endocrine-sensitive and -resistant ER positive breast cancer.ResultsWe demonstrate that MDM2 inhibition results in cell cycle arrest and increased apoptosis in p53-wildtype in vitro and in vivo breast cancer models, leading to potent anti-tumour activity. We find that endocrine therapy or CDK4/6 inhibition synergises with MDM2 inhibition but does not further enhance apoptosis. Instead, combination treatments result in profound regulation of cell cycle-related transcriptional programmes, with synergy achieved through increased antagonism of cell cycle progression. Combination therapy pushes cell lines resistant to fulvestrant or palbociclib to become senescent and significantly reduces tumour growth in a fulvestrant resistant patient derived xenograft model.ConclusionsWe conclude that MDM2 inhibitors in combination with ER degraders or CDK4/6 inhibitors represent a rational strategy for treating advanced, endocrine resistant ER-positive breast cancer, operating through synergistic activation of cell cycle co-regulatory programs.

Download Full-text

Tanshinone IIA Inhibits Osteosarcoma Growth through a Src Kinase-Dependent Mechanism

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2021/5563691 ◽

2021 ◽

Vol 2021 ◽

pp. 1-15

Author(s):

Chao Hu ◽

Xiaobin Zhu ◽

Taogen Zhang ◽

Zhouming Deng ◽

Yuanlong Xie ◽

...

Keyword(s):

Cell Cycle ◽

Cell Proliferation ◽

Signaling Pathways ◽

Cell Lines ◽

Src Kinase ◽

Akt Signaling ◽

Cellular Level ◽

Tanshinone Iia

Introduction. Osteosarcoma is a malignant tumor associated with high mortality rates due to the toxic side effects of current therapeutic methods. Tanshinone IIA can inhibit cell proliferation and promote apoptosis in vitro, but the exact mechanism is still unknown. The aims of this study are to explore the antiosteosarcoma effect of tanshinone IIA via Src kinase and demonstrate the mechanism of this effect. Materials and Methods. Osteosarcoma MG-63 and U2-OS cell lines were stable transfections with Src-shRNA. Then, the antiosteosarcoma effect of tanshinone IIA was tested in vitro. The protein expression levels of Src, p-Src, p-ERK1/2, and p-AKt were detected by Western blot and RT-PCR. CCK-8 assay and BrdU immunofluorescence assay were used to detect cell proliferation. Transwell assay, cell scratch assay, and flow cytometry were used to detect cell invasion, migration, and cell cycle. Tumor-bearing nude mice with osteosarcoma were constructed. The effect of tanshinone IIA was detected by tumor HE staining, tumor inhibition rate, incidence of lung metastasis, and X-ray. Results. The oncogene role of Src kinase in osteosarcoma is reflected in promoting cell proliferation, invasion, and migration and in inhibiting apoptosis. However, Src has different effects on cell proliferation, apoptosis, and cell cycle regulation among cell lines. At a cellular level, the antiosteosarcoma effect of tanshinone IIA is mediated by Src downstream of the MAPK/ERK and PI3K/AKt signaling pathways. At the animal level, tanshinone IIA played a role in resisting osteosarcoma formation by Src downstream of the MAPK/ERK and PI3K/AKt signaling pathways. Conclusion. Tanshinone IIA plays an antiosteosarcoma role in vitro and in vivo and inhibits the progression of osteosarcoma mediated by Src downstream of the MAPK/ERK and PI3K/AKt signaling pathways.

Download Full-text

Menadione reduces CDC25B expression and promotes tumor shrinkage in gastric cancer

Therapeutic Advances in Gastroenterology ◽

10.1177/1756284819895435 ◽

2020 ◽

Vol 13 ◽

pp. 175628481989543

Author(s):

Amanda Braga Bona ◽

Danielle Queiroz Calcagno ◽

Helem Ferreira Ribeiro ◽

José Augusto Pereira Carneiro Muniz ◽

Giovanny Rebouças Pinto ◽

...

Keyword(s):

Gastric Cancer ◽

Cell Cycle ◽

Cell Cycle Arrest ◽

Cell Lines ◽

Specific Inhibitor ◽

Gastric Carcinogenesis ◽

In Vivo Experiments ◽

Cycle Arrest

Background: Gastric cancer is one of the most incident types of cancer worldwide and presents high mortality rates and poor prognosis. MYC oncogene overexpression is a key event in gastric carcinogenesis and it is known that its protein positively regulates CDC25B expression which, in turn, plays an essential role in the cell division cycle progression. Menadione is a synthetic form of vitamin K that acts as a specific inhibitor of the CDC25 family of phosphatases. Methods: To better understand the menadione mechanism of action in gastric cancer, we evaluated its molecular and cellular effects in cell lines and in Sapajus apella, nonhuman primates from the new world which had gastric carcinogenesis induced by N-Methyl-N-nitrosourea. We tested CDC25B expression by western blot and RT-qPCR. In-vitro assays include proliferation, migration, invasion and flow cytometry to analyze cell cycle arrest. In in-vivo experiments, in addition to the expression analyses, we followed the preneoplastic lesions and the tumor progression by ultrasonography, endoscopy, biopsies, histopathology and immunohistochemistry. Results: Our tests demonstrated menadione reducing CDC25B expression in vivo and in vitro. It was able to reduce migration, invasion and proliferation rates, and induce cell cycle arrest in gastric cancer cell lines. Moreover, our in-vivo experiments demonstrated menadione inhibiting tumor development and progression. Conclusions: We suggest this compound may be an important ally of chemotherapeutics in the treatment of gastric cancer. In addition, CDC25B has proven to be an effective target for investigation and development of new therapeutic strategies for this malignancy.

Download Full-text

CDK4/6 inhibitors: a novel strategy for tumor radiosensitization

Journal of Experimental & Clinical Cancer Research ◽

10.1186/s13046-020-01693-w ◽

2020 ◽

Vol 39 (1) ◽

Author(s):

Yilan Yang ◽

Jurui Luo ◽

Xingxing Chen ◽

Zhaozhi Yang ◽

Xin Mei ◽

...

Keyword(s):

Cell Cycle ◽

Clinical Studies ◽

Cell Cycle Progression ◽

Combined Therapy ◽

Small Sample ◽

Combination Strategies ◽

Novel Strategy ◽

Underlying Mechanisms

Abstract Recently, the focus of enhancing tumor radiosensitivity has shifted from chemotherapeutics to targeted therapies. Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors are a novel class of selective cell cycle therapeutics that target the cyclin D-CDK4/6 complex and induce G1 phase arrest. These agents have demonstrated favorable effects when used as monotherapy or combined with endocrine therapy and targeted inhibitors, stimulating further explorations of other combination strategies. Multiple preclinical studies have indicated that CDK4/6 inhibitors exhibit a synergistic effect with radiotherapy both in vitro and in vivo. The principal mechanisms of radiosensitization effects include inhibition of DNA damage repair, enhancement of apoptosis, and blockade of cell cycle progression, which provide the rationale for clinical use. CDK4/6 inhibitors also induce cellular senescence and promote anti-tumor immunity, which might represent potential mechanisms for radiosensitization. Several small sample clinical studies have preliminarily indicated that the combination of CDK4/6 inhibitors and radiotherapy exhibited well-tolerated toxicity and promising efficacy. However, most clinical trials in combined therapy remain in the recruitment stage. Further work is required to seek optimal radiotherapy-drug combinations. In this review, we describe the effects and underlying mechanisms of CDK4/6 inhibitors as a radiosensitizer and discuss previous clinical studies to evaluate the prospects and challenges of this combination.

Download Full-text

EWS-FLI1-mediated tenascin-C expression promotes tumour progression by targeting MALAT1 through integrin α5β1-mediated YAP activation in Ewing sarcoma

British Journal of Cancer ◽

10.1038/s41416-019-0608-1 ◽

2019 ◽

Vol 121 (11) ◽

pp. 922-933 ◽

Cited By ~ 3

Author(s):

Shaohui He ◽

Quan Huang ◽

Jinbo Hu ◽

Lei Li ◽

Yanbin Xiao ◽

...

Keyword(s):

Cell Lines ◽

Ewing Sarcoma ◽

Nuclear Translocation ◽

Tumour Progression ◽

Underlying Mechanism ◽

Integrin Α5β1 ◽

Tenascin C ◽

Tumorigenesis And Progression

Abstract Background The extracellular matrix has been critically associated with the tumorigenesis and progression of Ewing sarcoma (ES). However, the regulatory and prognostic roles of tenascin-C (TNC) in ES remain unclear. Methods TNC expression was examined in specimens by immunohistochemistry, and the association of TNC expression with ES patient survival was also analysed. TNC-knockout cell lines were constructed using CRISPR/Cas9 methods. In vitro experiments and in vivo bioluminescent imaging using BALB/c nude mice were conducted to evaluate the effect of TNC on ES tumour progression. RNA sequencing was performed, and the underlying mechanism of TNC was further explored. Results TNC was overexpressed in ES tissue and cell lines, and TNC overexpression was associated with poor survival in ES patients. TNC enhanced cell proliferation, migration and angiogenesis in vitro and promoted ES metastasis in vivo. The oncoprotein EWS-FLI1 profoundly increased TNC expression by directly binding to the TNC promoter region. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) upregulation induced by Yes-associated protein (YAP) activation was responsible for TNC-regulated ES tumour progression. Activated integrin α5β1 signalling might be correlated with YAP dephosphorylation and nuclear translocation. Conclusions TNC may promote ES tumour progression by targeting MALAT1 through integrin α5β1-mediated YAP activation.

Download Full-text

Anticancer Activity of Cynomorium coccineum

Cancers ◽

10.3390/cancers10100354 ◽

2018 ◽

Vol 10 (10) ◽

pp. 354 ◽

Cited By ~ 7

Author(s):

Mouna Sdiri ◽

Xiangmin Li ◽

William Du ◽

Safia El-Bok ◽

Yi-Zhen Xie ◽

...

Keyword(s):

Cell Cycle ◽

Cell Death ◽

Anticancer Activity ◽

Cancer Cells ◽

Cell Lines ◽

Cancer Cell ◽

Cell Cycle Progression ◽

Cycle Progression

The extensive applications of Cynomorium species and their rich bioactive secondary metabolites have inspired many pharmacological investigations. Previous research has been conducted to examine the biological activities and numerous interesting pharmaceutical activities have been reported. However, the antitumor activities of these species are unclear. To understand the potential anticancer activity, we screened Cynomorium coccineum and Cynomorium songaricum using three different extracts of each species. In this study, the selected extracts were evaluated for their ability to decrease survival rates of five different cancer cell lines. We compared the cytotoxicity of the three different extracts to the anticancer drug vinblastine and one of the most well-known medicinal mushrooms Amaurederma rude. We found that the water and alcohol extracts of C. coccineum at the very low concentrations possessed very high capacity in decreasing the cancer cells viability with a potential inhibition of tumorigenesis. Based on these primitive data, we subsequently tested the ethanol and the water extracts of C. coccineum, respectively in in vitro and in vivo assays. Cell cycle progression and induction of programmed cell death were investigated at both biological and molecular levels to understand the mechanism of the antitumor inhibitory action of the C. coccineum. The in vitro experiments showed that the treated cancer cells formed fewer and smaller colonies than the untreated cells. Cell cycle progression was inhibited, and the ethanol extract of C. coccineum at a low concentration induced accumulation of cells in the G1 phase. We also found that the C. coccineum’s extracts suppressed viability of two murine cancer cell lines. In the in vivo experiments, we injected mice with murine cancer cell line B16, followed by peritoneal injection of the water extract. The treatment prolonged mouse survival significantly. The tumors grew at a slower rate than the control. Down-regulation of c-myc expression appeared to be associated with these effects. Further investigation showed that treatment with C. coccineum induced the overexpression of the tumor suppressor Foxo3 and other molecules involved in inducing autophagy. These results showed that the C. coccineum extract exerts its antiproliferative activity through the induction of cell death pathway. Thus, the Cynomorium plants appear to be a promising source of new antineoplastic compounds.

Download Full-text

Inhibition of Wnt/β-Catenin Signaling in Neuroendocrine Tumors In Vitro: Antitumoral Effects

Cancers ◽

10.3390/cancers12020345 ◽

2020 ◽

Vol 12 (2) ◽

pp. 345

Author(s):

Xi-Feng Jin ◽

Gerald Spöttl ◽

Julian Maurer ◽

Svenja Nölting ◽

Christoph Josef Auernhammer

Keyword(s):

Cell Cycle ◽

Cell Viability ◽

Cell Lines ◽

Neuroendocrine Tumors ◽

Density Lipoprotein ◽

Time Dependent ◽

Dependent Manner ◽

Antitumor Properties

Background and aims: Inhibition of Wnt/β-catenin signaling by specific inhibitors is currently being investigated as an antitumoral strategy for various cancers. The role of Wnt/β-catenin signaling in neuroendocrine tumors still needs to be further investigated. Methods: This study investigated the antitumor activity of the porcupine (PORCN) inhibitor WNT974 and the β-catenin inhibitor PRI-724 in human neuroendocrine tumor (NET) cell lines BON1, QGP-1, and NCI-H727 in vitro. NET cells were treated with WNT974, PRI-724, or small interfering ribonucleic acids against β-catenin, and subsequent analyses included cell viability assays, flow cytometric cell cycle analysis, caspase3/7 assays and Western blot analysis. Results: Treatment of NET cells with WNT974 significantly reduced NET cell viability in a dose- and time-dependent manner by inducing NET cell cycle arrest at the G1 and G2/M phases without inducing apoptosis. WNT974 primarily blocked Wnt/β-catenin signaling by the dose- and time-dependent downregulation of low-density lipoprotein receptor-related protein 6 (LRP6) phosphorylation and non-phosphorylated β-catenin and total β-catenin, as well as the genes targeting the latter (c-Myc and cyclinD1). Furthermore, the WNT974-induced reduction of NET cell viability occurred through the inhibition of GSK-3-dependent or independent signaling (including pAKT/mTOR, pEGFR and pIGFR signaling). Similarly, treatment of NET cells with the β-catenin inhibitor PRI-724 caused significant growth inhibition, while the knockdown of β-catenin expression by siRNA reduced NET tumor cell viability of BON1 cells but not of NCI-H727 cells. Conclusions: The PORCN inhibitor WNT974 possesses antitumor properties in NET cell lines by inhibiting Wnt and related signaling. In addition, the β-catenin inhibitor PRI-724 possesses antitumor properties in NET cell lines. Future studies are needed to determine the role of Wnt/β-catenin signaling in NET as a potential therapeutic target.

Download Full-text

Arsenic Trioxide Shows Synergistic Anti-Myeloma Effects When Combined with Bortezomib and Melphalan In Vitro and Helps Overcome Resistance of Multiple Myeloma Cells to These Treatments in Vivo.

Blood ◽

10.1182/blood.v104.11.2467.2467 ◽

2004 ◽

Vol 104 (11) ◽

pp. 2467-2467

Author(s):

Richard A. Campbell ◽

Haiming Chen ◽

Daocheng Zhu ◽

Janice C. Santos ◽

Benjamin Bonavida ◽

...

Keyword(s):

Arsenic Trioxide ◽

Cell Lines ◽

Combined Therapy ◽

In Vivo Studies ◽

Low Doses ◽

Drug Resistant ◽

Early Results ◽

Post Implantation

Abstract Arsenic trioxide (ATO) induces apoptosis of plasma cells through a number of mechanisms including inhibiting DNA binding by NF-κB. These results suggest that this agent may be synergistic when combined with other active anti-myeloma drugs. To evaluate this we examined the effect of ATO alone and in combination with anti-myeloma treatments evaluated in vitro with MTT assays and using our severe combined immunodeficient (SCID)-hu murine myeloma models. First, we determined the effects of combining ATO with bortezomib or melphalan on the myeloma cell lines RPMI8226 and U266. Cell proliferation assays demonstrated marked synergistic anti-proliferative effects of ATO at concentrations ranging from 5x10−5M – 5x10−9M and melphalan concentrations ranging from 3x10−5M – 3x10−9M. Similar effects were observed when these cell lines were treated with bortezomib and varying concentrations of ATO (5x10−5 M – 5x10−10 M). We also investigated the potential of ATO to increase the efficacy of anti-myeloma therapies in our SCID-hu murine model LAGλ–1 (Yang H et al. Blood 2002). Each SCID mouse was implanted with a 0.5 cm3 LAGλ–1 tumor fragment into the left hind limb muscle. Mice were treated with ATO alone at 6.0 mg/kg, 1.25 mg/kg, 0.25 mg/kg, and 0.05 mg/kg intraperitoneally (IP) daily x5/week starting 19 days post-implantation. Mice receiving the highest dose of ATO (6.0 mg/kg) showed marked inhibition of tumor growth and reduction of paraprotein levels while there was no effect observed in all other treatment groups. Next, 27 days following implantation of our LAGλ–1 intramuscular (IM) tumor, LAGλ–1 mice were treated with ATO (1.25 mg/kg) IP, bortezomib (0.25 mg/kg), or the combination of both drugs at these doses in the schedules outlined above. ATO or bortezomib treatment alone had no anti-myeloma effects at these low doses consistent with our previous results whereas there was a marked decrease in both tumor volume (57%) and paraprotein levels (53%) in mice receiving the combined therapy. The combination of melphalan and ATO was also evaluated in this model. LAGλ–1 bearing mice received therapy with melphalan IP x1/weekly at 12.0 mg/kg, 6.0 mg/kg, 0.6 mg/kg, and 0.06 mg/kg starting 22 days post-implantation and showed no anti-myeloma effects. Twenty-eight days following implantation of LAGλ–1 tumor, mice received ATO (1.25 mg/kg) or melphalan (0.6 mg/kg) alone at doses without anti-myeloma effects, or the combination of these agents at these doses. The animals treated with these drugs alone showed a similar growth and increase in paraprotein levels to control mice whereas the combination of ATO and melphalan at these low doses markedly suppressed the growth of the tumor by >50% and significantly reduced serum paraprotein levels. These in vitro and in vivo studies suggest that the addition of ATO to other anti-myeloma agents is likely to result in improved outcomes for patients with drug resistant myeloma. Based on these results, these combinations are now in clinical trials with promising early results for patients with drug resistant myeloma.

Download Full-text