Mari I. Suominen

Survival Benefit With Radium-223 Dichloride in a Mouse Model of Breast Cancer Bone Metastasis

BACKGROUND Bone metastases are associated with increased morbidity and poor prognosis in breast cancer patients. Radium-223 dichloride is a calcium mimetic that localizes to bone, providing targeted therapy for skeletal metastasis. METHODS We investigated the mode of action of radium-223 dichloride using breast cancer cell, osteoclast, and osteoblast cultures as well as a mouse model of breast cancer bone metastasis. A single dose of radium-223 dichloride was used in three different settings mimicking the prevention or treatment of bone metastasis. Disease progression was monitored using fluorescence and radiographic imaging and histological analyses. The effect of radium-223 dichloride alone and in combination with doxorubicin or zoledronic acid on survival of mice was analyzed by Kaplan-Meier methods. All statistical tests used were two-sided. RESULTS Radium-223 dichloride incorporated into bone matrix and inhibited proliferation of breast cancer cells and differentiation of osteoblasts and osteoclasts (all P values < .001) in vitro. In an established bone metastasis setting, radium-223 dichloride prevented tumor-induced cachexia (0/14 vs 7/14 control mice) and decreased osteolysis by 56% and tumor growth by 43% (all P values < .05). Radium-223 dichloride induced double-strand DNA breaks in cancer cells in vivo. Finally, radium-223 dichloride extended survival as a monotherapy (29.2 days, 95% confidence interval [CI] = 26.6 to 31.8 days, P = .039) and in combination with zoledronic acid (31.4 days, 95% CI = 28.8 to 34.0 days, P = .004) or doxorubicin (31.5 days, 95% CI = 29.5 to 33.5 days, P < .001) compared to the vehicle group (24.9 days, 95% CI = 23.4 to 26.4 days). Similar but even more pronounced effects were observed when radium-223 dichloride was administered in a preventive or micrometastatic setting. CONCLUSIONS Our findings strongly support the development of radium-223 dichloride for the treatment of breast cancer patients with or at high risk of developing bone metastases.

Radium-223 Inhibits Osseous Prostate Cancer Growth by Dual Targeting of Cancer Cells and Bone Microenvironment in Mouse Models

Purpose: Radium-223 dichloride (radium-223, Xofigo), a targeted alpha therapy, is currently used for the treatment of patients with castration-resistant prostate cancer (CRPC) with bone metastases. This study examines the mode-of-action and antitumor efficacy of radium-223 in two prostate cancer xenograft models. Experimental Design: Mice bearing intratibial LNCaP or LuCaP 58 tumors were randomized into groups (n = 12–17) based on lesion grade and/or serum PSA level and administered radium-223 (300 kBq/kg) or vehicle, twice at 4-week intervals. X-rays and serum samples were obtained biweekly. Soft tissue tumors were observed macroscopically at sacrifice. Tibiae were analyzed by gamma counter, micro-CT, autoradiography and histology. Results: Radium-223 inhibited tumor-induced osteoblastic bone growth and protected normal bone architecture, leading to reduced bone volume in LNCaP and abiraterone-resistant LuCaP 58 models. Furthermore, radium-223 resulted in lower PSA values and reduced total tissue and tumor areas, indicating that treatment constrains prostate cancer growth in bone. In addition, radium-223 suppressed abnormal bone metabolic activity as evidenced by decreased number of osteoblasts and osteoclasts and reduced level of the bone formation marker PINP. Mode-of-action studies revealed that radium-223 was deposited in the intratumoral bone matrix. DNA double-strand breaks were induced in cancer cells within 24 hours after radium-223 treatment, and PSA levels were significantly lower 72 hours after treatment, providing further evidence of the antitumor effects. Conclusions: Taken together, radium-223 therapy exhibits a dual targeting mode-of-action that induces tumor cell death and suppresses tumor-induced pathologic bone formation in tumor microenvironment of osseous CRPC growth in mice. Clin Cancer Res; 23(15); 4335–46. ©2017 AACR.

Improved Statistical Modeling of Tumor Growth and Treatment Effect in Preclinical Animal Studies with Highly Heterogeneous Responses In Vivo

Purpose: Preclinical tumor growth experiments often result in heterogeneous datasets that include growing, regressing, or stable growth profiles in the treatment and control groups. Such confounding intertumor variability may mask the true treatment effects especially when less aggressive treatment alternatives are being evaluated. Experimental design: We developed a statistical modeling approach in which the growing and poorly growing tumor categories were automatically detected by means of an expectation-maximization algorithm coupled within a mixed-effects modeling framework. The framework is implemented and distributed as an R package, which enables model estimation and statistical inference, as well as statistical power and precision analyses. Results: When applied to four tumor growth experiments, the modeling framework was shown to (i) improve the detection of subtle treatment effects in the presence of high within-group tumor variability; (ii) reveal hidden tumor subgroups associated with established or novel biomarkers, such as ERβ expression in a MCF-7 breast cancer model, which remained undetected with standard statistical analysis; (iii) provide guidance on the selection of sufficient sample sizes and most informative treatment periods; and (iv) offer flexibility to various cancer models, experimental designs, and treatment options. Model-based testing of treatment effect on the tumor growth rate (or slope) was shown as particularly informative in the preclinical assessment of treatment alternatives based on dietary interventions. Conclusions: In general, the modeling framework enables identification of such biologically significant differences in tumor growth profiles that would have gone undetected or had required considerably higher number of animals when using traditional statistical methods. Clin Cancer Res; 18(16); 4385–96. ©2012 AACR.

Abstract 5712: Alpharadin (Radium-223 chloride) completely prevents tumor growth in bone and increases survival in a mouse model of breast cancer bone metastases in preventive and micro-metastatic settings

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Radium-223 chloride is an alpha-emitting radiopharmaceutical that has been shown to improve overall survival in the phase III clinical study (ALSYMPCA) in the treatment of castration resistant prostate cancer with bone metastases (Parker et al. ECCO/ESMO 2011, abstract LBA1). As a calcium mimetic, radium-223 localizes to bone, where the emission of alpha-particles provide an efficient and localized radiation treatment to metastatic skeletal tumor lesions. As previously reported, radium-223 decreases osteolysis and also tumor burden in established model of breast cancer bone metastasis in nude mice (Suominen et al. AACR 2011, abstract 2664). In this study, we investigated the effects of radium-223 on the development of breast cancer bone metastases when administered in the preventive and micro-metastastic settings. The effects of radium-223 were studied in a breast cancer bone metastatic model using intra-cardiac injection of human MDA-MB-231SA/GFP cells in nude mice at day 0. In the first study, the animals were randomized into four groups (n=7) and dosed with either vehicle or a single dose of radium-223 (300 kBq/kg) at days -1, 2 or 15. Three mice were also sacrificed at day 2 for immunohistochemical (pan-cytokeratin and GFP) detection of tumor cells in the bone marrow. Radiography and fluorescence imaging were performed at sacrifice (day 25). Tumor burden was also analysed from mid-sagittal sections of both hind limbs. The second study was a survival study, in which the animals were randomized to three groups (n=12) and dosed with either vehicle or a single dose of radium-223 (300 kBq/kg) at days -1 or 2. Radiography and fluorescence imaging were performed only on animals surviving to day 50. In the first study there were disseminated tumor cells in the bone marrow of all three animals (altogether 18/18 positive sections) sacrificed at day 2, as detected by IHC staining. Radium-223 decreased whole body tumor burden by 81, 84 and 55% and osteolysis by 98, 99.6 and 82%, when administered at days -1, 2 or 15, respectively. No tumor foci were detected in the bone sections of mice treated at days -1 and 2, and tumor area was decreased by 65% in animals treated at day 15. In the survival study, median survival was 24.5 days in the control group, 39.5 days (p <0.001 vs ctrl) in the group administered at day -1, and 35.5 days (p<0.001 vs ctrl) in the group administered at day 2. Three of twelve animals, all administered at day -1, survived until day 50 and two of them had only minimal residual disease. In summary, Alpharadin (radium-223) administered in a preventive or micro-metastatic setting completely prevented progression of osteolytic breast cancer bone metastases and increased survival in this preclinical model. These findings strongly support the clinical development of radium-223 for patients at risk of developing bone metastases. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5712. doi:1538-7445.AM2012-5712

Abstract 1803: A new spectrum-selective cathepsin inhibitor, VBY-825, inhibits bone destruction in a syngeneic 5TGM1 multiple myeloma mouse model

Multiple myeloma (MM) is the second most common blood cancer after non Hodgkin lymphoma. It is a monoclonal B-cell neoplasia with clinical hallmarks of multiple osteolytic lesions causing bone pain, fractures and hypercalcemia. Chemo- or radiotherapy may induce remissions, but MM is generally thought to be incurable. Our aim was to observe the effects of a cathepsin inhibitor VBY-825 on bone lesions and tumor burden in the syngeneic 5TGM1 mouse MM model using immunocompetent C57BL/KaLwRij mice. VBY-825 is a potent inhibitor of cathepsins K, L, B, V, and S. 5TGM1 cells were inoculated via tail vein in 7 weeks old female C57BL/KaLwRij mice, which were divided to 4 groups: Control group received vehicle of VBY-825 (5% dextrose 10 ml/kg daily), Control group received bortezomib vehicle (3 ml/kg twice a week), Reference group received bortezomib (0.5 mg/kg twice a week) and Study group received VBY-825 (100 mg/kg daily). Administration of all compounds began one day before tumor cell inoculation and continued until day 34. Disease progression was followed by measuring the serum levels of paraprotein (IgG2b) and TRACP 5b, radiography, and body weight. The animals were sacrificed 5 weeks after inoculation, examined macroscopically, and their bones were collected for histomorphometric analysis. The reference compound bortezomib had no effects on body weight but it delayed the disease progression based on IgG2b measurements. It also decreased the number and total area of osteolytic lesions, but not mean osteolytic lesion area (MOLA). VBY-825 had no effect on body weight or IgG2b level, frequency of soft tissue tumors or intraosseous tumor area. VBY-825 decreased total and MOLA, consistent with inhibited resorption. There was also a trend of increased relative trabecular bone area. Serum TRACP 5b activity in the VBY-825 treated group did not differ from the respective vehicle group, whereas the number of osteoclasts at tumor-bone interface was increased in VBY-825 treated animals. These findings suggest that VBY-825 decreased osteoclast function and resorption activity without decreasing the number of osteoclasts In conclusion, VBY-825 had no effects on tumor growth but it inhibited bone destruction in this mouse model of MM, which is consistent with its potency on cathepsin S and K, which are known to be important in osteoclast-mediated bone resorption. VBY-825 is a promising candidate for the treatment of tumor-associated bone disease. Citation Format: Mari I. Suominen, Johanna Tuomela, Esa Alhoniemi, Katja M. Fagerlund, Jukka P. Rissanen, Jussi M. Halleen, Leslie J. Holsinger. A new spectrum-selective cathepsin inhibitor, VBY-825, inhibits bone destruction in a syngeneic 5TGM1 multiple myeloma mouse model. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1803. doi:10.1158/1538-7445.AM2014-1803

Abstract 4968: Importance of tumor microenvironment in the preclinical estrogen receptor positive breast cancer- Primary tumor and bone metastasis models

Estrogen receptor positive (ER+) breast cancer has ability to metastasize to bone in high frequency. Bone is known to be fertile soil for metastasized cancer cells to survive and in turn, metastasized tumor cells alter normally balanced bone environment. Prevention and treatment of bone metastasis is challenging and better understanding why bone metastasis are resistant to current therapies is needed. Aim of the present study was to explore the role of tumor microenvironment and estrogen supplementation on growth of primary breast cancer tumor and bone metastasis to establish predictive ER+ breast cancer models for drug development. ER+ human breast cancer MCF-7 cells were inoculated into mammary fat pad and in the tibia of female athymic nude mice. Mice received either hormonal supplementation (17-beta estradiol pellet, E2) or placebo. Tumor growth was followed for 5 and 9 weeks. From one group, E2 supplementation was removed on study week 5 and tumor growth was followed for 4 weeks. During the study, blood samples were collected for serum steroid concentration measurements and at the end, histopathological evaluation and immunohistochemical (IHC) stainings were performed to examine tumor steroid hormone receptor expression. Orthotopic MCF-7 tumor growth was clearly hormone dependent. E2 supplementation, that increased serum estradiol for app. 3-fold, supported tumor growth and when E2 was removed, tumor size decreased and no tumor growth was observed thereafter. In the full absence of E2 supplement, no orthotopic tumor growth was observed. In contrast, when MCF-7 cells were inoculated into tibia, tumor growth was observed both with and without E2 supplement. IHC stainings confirmed orthotopic tumor to express ER, PR and AR when animals received E2. After E2 removal, orthotopic tumors expressed still ER and AR but no longer PR. Also intratibial tumors expressed ER and PR in the presence of E2, but no PR in the absence of E2 supplement. E2 is needed to support MCF-7 tumor growth when cancer cells are inoculated orthotopically into mammary fat pad. No orthotopic tumor growth is observed in the absence of E2 supplement. In contrast, in the bone microenvironment, MCF-7 cells form tumor even in the absence of E2 supplement. Results highlight importance of tumor microenvironment in the breast cancer progression and also refer why tumor in the different sites may be resistant to therapy. Taking together, when developing new therapies against breast cancer, focus should be addressed not only on primary tumor growth but also on bone metastasis where cancer cells are under influence of bone environment. Citation Format: Jenni Bernoulli, Mari I. Suominen, Tiina Kahkonen, Jenni Maki-Jouppila, Jussi M. Halleen, Riikka Oksala. Importance of tumor microenvironment in the preclinical estrogen receptor positive breast cancer- Primary tumor and bone metastasis models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4968. doi:10.1158/1538-7445.AM2017-4968

Abstract A109: Radium-223 dichloride inhibits tumor growth and tumor-induced bone growth in osteoblastic prostate cancer models

Radium-223 dichloride (radium-223), an alpha particle-emitting calcium-mimetic, improves overall survival in prostate cancer patients with symptomatic bone metastases. We have defined radium-223 mode-of-action and efficacy in two clinically relevant prostate cancer xenograft models demonstrating PSA expression and osteoblastic growth upon intratibial inoculation of cancer cells. Immunocompromised male mice were inoculated with human LNCaP or patient-derived LuCaP 58 prostate cancer cells in the intratibial compartment and subsequently stratified into treatment groups based on lesion grade and/or serum PSA levels. Radium-223 (300 kBq/kg) or vehicle was administered intravenously, two times at 4-week intervals during the experiment. X-rays and serum samples were obtained biweekly and at sacrifice. Soft tissue tumors were examined macroscopically at sacrifice and tissue samples were collected and processed for γ-counter measurements, micro-CT, autoradiography and histology. Radium-223 treatment inhibited tumor-induced osteoblastic bone growth as indicated by reduced bone volume and surface in LNCaP and LuCaP 58 prostate cancer mouse models. In addition, radium-223 treatment suppressed metabolic activity in bone as evidenced by decreased number of osteoblasts and osteoclasts relative to bone surface and reduced levels of the bone formation marker PINP. Radium-223 resulted in lower PSA values as early as two weeks after the first dose, indicating constrained tumor growth following treatment. This phenomenon was further supported by reduced total bone lesion tissue and tumor area in LNCaP and LuCaP 58 models and increased percentage of necrotic tumor area in the LuCaP 58 model in radium-223-treated mice as compared to vehicle-treated mice. Moreover, DNA double-strand breaks were increased in cancer cells 24 hours post radium-223 treatment in the LuCaP 58 model providing further evidence of anti-tumor effects. Radium-223-treated mice exhibited less visceral metastases in the LuCaP 58 model (not significant). Based on autoradiography, radium-223 was deposited in the intratumoral bone matrix and in conjunction with osteoblasts in osteoblastic metastases. Our results demonstrate that radium-223 dichloride is successfully incorporated into the intratumoral bone matrix and inhibits tumor growth in both cell line- and patient-derived osteoblastic prostate cancer metastasis models. Given the α-particle range of 50-80 μm, potent radiation effects on the tumor microenvironment are evident whereas relevant effects on the more distant bone marrow are not expected. Taken together, radium-223 therapy exhibits a dual mode-of-action that impacts tumor growth and tumor-induced bone reaction, both important players in the destructive vicious cycle of osteoblastic bone metastasis in prostate cancer. Citation Format: Mari I. Suominen, Katja M. Fagerlund, Dominik Mumberg, Karl Ziegelbauer, Sanna-Maria Kakonen, Jussi M. Halleen, Robert L. Vessella, Arne Scholz. Radium-223 dichloride inhibits tumor growth and tumor-induced bone growth in osteoblastic prostate cancer models. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A109.

Abstract 5202: Additive benefits of radium-223 dichloride and bortezomib combination in a syngeneic 5TGM1 multiple myeloma mouse model

Radium-223 dichloride (radium-223, Xofigo®), a targeted alpha-therapy, improves overall survival in prostate cancer patients with bone metastases. It inhibits disease progression by reducing tumor growth and tumor-induced pathological bone reaction in breast and prostate cancer mouse models. Radium-223 is actively incorporated into the bone matrix by osteoblasts. Multiple myeloma (MM) is characterized by increased osteoclast and reduced or no osteoblast activity. Bortezomib (Velcade®), a treatment for MM, restores the impaired osteoblast activity in MM. Here, we report the effects of radium-223, bortezomib and their combination on myeloma cell proliferation in vitro and on myeloma bone disease model in mice. Proliferation assays were performed with human plasma cell leukemia (JJN-3, L-363), human MM (LP-1, MOLP-8, RPMI-8226 and OPM-2), and mouse MM (5TGM1) cells. Corresponding in vivo effects were studied in a syngeneic 5TGM1 mouse MM model. Female C57BL/KaLwRij mice (7 weeks old, n=15/group) were inoculated with 5TGM1 cells via tail vein and 26 days later, radium-223 (300 kBq/kg, single iv injection) and/or bortezomib (1 mg/kg ip, twice a week; total of 3 doses) or vehicle control were administered. The development of osteolytic lesions was detected by radiography. Hind limbs were used for histological analyses and total activity measurement was performed by a gamma-counter. TRAP-stained osteoclasts were counted at tumor-bone interface. Bortezomib inhibited proliferation of all cancer cell lines tested at 25 nM (JJN3 and OPM-2 at 2.5 nM) and radium-223 at 0.8 kBq/ml (L-363 and MOLP-8 at 0.2 kBq/ml) concentrations. Additive effects were observed with combination treatment in vitro. The 5TGM1 in vivo model demonstrated that both bortezomib and radium-223 decreased osteolytic lesion area as monotherapy (p In conclusion, radium-223 dichloride (Xofigo®) therapy in combination with bortezomib decreased osteolytic lesion area and almost completely eradicated tumor-associated osteoclasts in a mouse model of myeloma bone disease. Incorporation of radium-223 to bone matrix was improved, possibly via induction of osteoblast activity by bortezomib. These data suggest that combination of radium-223 and bortezomib could be a new effective therapy in MM, which is currently being investigated in a Phase Ib/II trial in patients with early relapsed MM (NCT02928029). Citation Format: Mari I. Suominen, Jukka P. Rissanen, Anniina Luostarinen, Katja M. Fagerlund, Birgitta Sjoholm, Esa Alhoniemi, Sanna-Maria Kakonen, Dominik Mumberg, Jussi M. Halleen, Karl Ziegelbauer, Arne Scholz. Additive benefits of radium-223 dichloride and bortezomib combination in a syngeneic 5TGM1 multiple myeloma mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5202. doi:10.1158/1538-7445.AM2017-5202

Abstract 4207: Selective drug sensitivity score (DSS) for indolent and aggressive prostate cancer cell lines

Prostate cancer (PC) is the most common malignancy in men and the second leading cause of cancer-related deaths. The majority of the PCs are classified as adenocarcinomas characterized by the expression of androgen receptor (AR) and prostate-specific antigen (PSA). Two of the most commonly used cell lines are LNCaP and PC-3 cells, derived from lymph node and bone metastases, respectively. Also VCaP cells, derived from vertebral metastases, are widely used in prostate cancer research. It has been well established that LNCaP and VCaP cells represent the conventional indolent form of PC expressing AR and PSA and are androgen-dependent. PC-3 cells, on the other hand, do not express AR and PSA, are androgen-independent, and represent the highly aggressive form. The drug sensitivity of the cell lines was assessed by applying a large panel of drugs covering cancer chemotherapeutics and clinically available and emerging drugs including conventional chemotherapy, kinase inhibitors, metabolic modifiers, rapalogs, differentiating/epigenetic modifiers, kinesin inhibitors, apoptotic modulators, NSAIDs, hormone therapy, immunomodulators and HSP inhibitors. A panel of 460 compounds was tested in five concentrations covering a 10.000-fold drug-relevant concentration range in 384-well format. Cells were seeded to pre-drugged plates, followed by cell viability measurements (CellTiter-Glo) after 72 hours. Maximal and minimal responses to drugs were analyzed, the EC50 values were calculated and Drug Sensitivity Score (DSS) was calculated for each drug as a measure of reduced viability. A selective Drug Sensitivity Score (sDSS) was calculated to identify the selective drug response pattern of each three cancer cell lines. As expected, the results indicate that LNCaP and VCaP cells in general were more sensitive to drugs of different categories than PC-3 cells. According to DSS analysis, all three cell lines showed sensitivity to conventional chemotherapy and kinase inhibitors. However, PC-3 cells were more sensitive to kinase inhibitors than conventional chemotherapy. Determining sDSS revealed specific sensitivities of each cell line. LNCaP cells were sensitive to kinase inhibitors, such as mTOR and AKT inhibitors. Also VCaP cells showed selective sensitivity to kinase inhibitors, especially Aurora kinase and IGF1R inhibitors. In addition to kinase inhibitors, VCaP cells were selectively sensitive to HDAC inhibitors. Furthermore, PC-3 cells were sensitive to e.g. CDK inhibitors. We conclude that the cell-based compound screening combined with DSS and sDSS analysis provides a possibility to profile cellular responses to an extensive collection of anti-cancer compounds enabling repurposing of existing drugs to new indications, identification of vulnerabilities in different types of cancer cells and functional investigation of cellular pathways behind drug sensitivity or resistance. Citation Format: Jenni Maki-Jouppila, Jenni Bernoulli, Johanna Tuomela, Mari I. Suominen, Jussi M. Halleen, Sanna Timonen, Elina Huovari, Katja Suomi, Swapnil Potdar, Paivi Ostling, Jani Saarela, Katja M. Fagerlund. Selective drug sensitivity score (DSS) for indolent and aggressive prostate cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4207. doi:10.1158/1538-7445.AM2017-4207

Abstract 3838: Drug sensitivity profile of 5TGM1 murine multiple myeloma cell line emphasizes the translational potential of the syngeneicin vivomodel

Multiple myeloma (MM) is the second most common hematologic malignancy that originates from B-cells (plasma cells) and causes 2% of cancer-related deaths. Symptoms of MM include bone pain caused by multiple osteolytic lesions, pathologic fractures, and hypercalcemia. Typically, MM has a low growth fraction and it is highly dependent on the microenvironment. These properties have made it hard to target by conventional chemotherapy, but could now be exploited by novel stroma-targeting drugs and immunotherapy. These new approaches underline the need for well characterized models with functional immune system and appropriate tumor microenvironment. To gain additional information supporting the use of the syngeneic 5TGM1 murine multiple myeloma model in drug development, we tested drug sensitivity of 5TGM1 cells by screening an extensive panel of drugs. The compound library consisting of 460 compounds included conventional chemotherapy, kinase inhibitors, metabolic modifiers, rapalogs, differentiating/epigenetic modifiers, kinesin inhibitors, apoptotic modulators, NSAIDs, hormone therapy, immunomodulators and HSP inhibitors. The compounds were tested in five concentrations covering a 10.000-fold drug-relevant concentration range in 384-well format. Cells were seeded to plates with a compound library, followed by cell viability measurements (CellTiter-Glo) after 72 hours. Maximal and minimal responses to drugs were analyzed, and the EC50 values were calculated. Drug Sensitivity Score (DSS) was calculated for each drug as a measure of reduced viability. According to DSS analysis, 5TGM1 cells showed sensitivity to conventional chemotherapy, such as antimitotic drugs, and kinase inhibitors, such as MEK1/2 inhibitors. In addition, the cells showed particular sensitivity to several HSP90 inhibitors currently in phase I/II clinical development for MM. Lenalidomide and pomalidomide, efficient in treating multiple myeloma in humans, both gave low DSS value indicating that 5TGM1 cells are not sensitive to these drugs, which is expected because they do not bind to murine form of the target cereblon. In contrast, 5TGM1 cells were highly sensitive to the proteasome inhibitor bortezomib (DSS 32.2), which is currently in clinical use. In conclusion, the murine 5TGM1 cells show sensitivity to various MM drugs used in the clinic and under development. Evaluating the effects of the microenvironment on the growth and drug sensitivity of 5TGM1 cells in vitro and in vivo will be essential. Furthermore, the cell-based compound screening combined with DSS analysis provides a possibility to profile cellular responses to an extensive collection of anti-cancer compounds enabling identification of vulnerabilities in cancer cells and functional investigation of cellular pathways behind drug sensitivity or resistance. Citation Format: Jenni Maki-Jouppila, Jenni Bernoulli, Mari I. Suominen, Tiina Kahkonen, Jussi M. Halleen, Sanna Timonen, Elina Huovari, Katja Suomi, Swapnil Potdar, Maria Nurmi, Paivi Ostling, Jani Saarela, Katja M. Fagerlund. Drug sensitivity profile of 5TGM1 murine multiple myeloma cell line emphasizes the translational potential of the syngeneic in vivo model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3838. doi:10.1158/1538-7445.AM2017-3838