Abstract 452: Novel autophagy inhibitory strategies to overcome chemotherapy resistance in multiple myeloma

Multiple myeloma (MM) is an incurable disease. Classical chemotherapeutics including bortezomib, melphalan, lenalidomide and thalidomide have greatly enhanced survival times. Unfortunately, patients typically relapse and become refractory with an average survival of 5 years post-diagnosis. Our emerging studies demonstrate a novel role for ULK3 in regulating autophagy in MM, a key program that sustains cell survival under times of stress and has been implicated as a major mechanism of proteasome inhibitor (PI) resistance. MM is known to be highly dependent on autophagy and, currently, specific ULK3 inhibitors are lacking. We posit that by targeting this marker in chemotherapy resistant MM patients, we can circumvent alternative metabolic routes and resensitize to standard of care proapoptotic therapy. We performed RNASeq analysis of CD138+ MM cells derived from patients across the disease stages spectrum (n=815) to confirm the role of ULK3 in disease progression and resistance to chemotherapy. We developed novel inhibitors SG3014/MA9060 that target multiple kinases including ULK3 (EC50 90nM) as well as BRD4. BRD4 is a known driver of MYC and its expression is increased in refractory MM. The BRD4 inhibitor, JQ1, effectively impairs the tumorigenic potential of MM but resistance has also been noted. We determined the efficacy of MA9060 for the treatment of CD138+ MM isolated from naive and refractory patients using a novel ex vivo high throughput platform developed at Moffitt.ULK3 is highly associated with MM stage of the disease. Refractory MM patients have increased autophagy activity with significantly higher expression of ULK3 in refractory patients and in drug resistant cell lines (immunoblotting U266 vs U266-PSR; RPMI-8226 vs RPMI-8226-B25; ABNL vs V10 resistant cells).Genetic ablation of ULK3 by siRNA in U266 and 8226 cell lines results in rapid cessation of the downstream autophagy proteins (ULK1, ATG13, pATG13) and MM cell death within 72h of transduction. Increased concentrations of autophagy inhibitors MA9060/SG3014 progressively decreased CMYC and ULK3 levels, as measured by immunoblotting in U266 cells. In vivo preclinical model of U266Luc tail vein injection proved our drugs are highly effective in reducing tumor dissemination and extending overall survival (CTRL untreated n=65 days vs MA9060 n=110). Importantly, we noted no overt toxicity and protected effect against myeloma-induced bone disease. This novel class of drug works synergistically with PI and can re-sensitize PI resistant disease to these effective therapies. We also show by EMMA ex vivo platform that MA9060 is highly effective for the treatment of CD138+ MM cells isolated from patients with refractory disease.ULK3 represents a novel target for treatment of MM refractory disease. Our dual inhibitors can increase overall survival in vivo and ex vivo, therefore we expect to quickly translate our novel molecules to the clinic.

Citation Format: Marilena Tauro, Tao Li, Mark Meads, Praneeth R. Sudalagunta, Raghunandan R. Alugubelli, Nicholas J. Lawrence, Ernst Schonbrunn, Harshani Lawrence, Kenneth H. Shain, Conor C. Lynch. Novel autophagy inhibitory strategies to overcome chemotherapy resistance in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 452.

Abstract PD3-10: Dual epigenetic/autophagy inhibition as a novel strategy to tackle triple negative breast cancer

Clinical Significance: Despite initial response to therapies, patients with triple negative breast cancer (TNBC) have the highest risk of metastatic relapse within 5 years of diagnosis. There is an urgent need for better treatments for this deadly disease. To this end, understanding the molecular drivers can reveal novel therapeutic targets. Background: The TNBC oncogenic program is known to be driven by MYC. MYC expression is regulated by bromodomain proteins and several bromodomain inhibitors such as JQ1 have proven effective at inhibiting MYC expression. However, resistance can occur rapidly upon activation of alternative cell survival mechanisms, such as autophagy. TNBC is noted for its elevated basal autophagy. Interestingly, publicly available datasets show that ULK3, an initial effector of the autophagy program, is upregulated in TNBC patients while the opposite is observed for the classical autophagy initiator ULK1. Moreover, TNBC patients with low ULK3 expression levels tend to achieve longer relapse free survival (RFS) than higher expression cohort, in opposition to ULK1. Importantly, ULK3 has not been investigated to date in regulating TNBC cell intrinsic autophagy and no drugs exist that can inhibit ULK3. Methods and Results: Given the importance of MYC and ULK3 in TNBC progression, our team developed a novel class of small molecules, namely dual BRD4/ULK3 inhibitors, that are superior to JQ1 alone in limiting TNBC viability. In vitro data demonstrate that TNBC cells are more sensitive to the cytotoxic activity of the dual inhibitors compared to other breast cancer subtypes. Further investigation through western blot analysis confirms the effectiveness of these novel dual inhibitors in abrogating MYC expression overtime, and completely blocking the autophagy program (measured by downstream ULK3, ULK1, LC3B, p62 protein levels), resulting in cell death. Interestingly, the human cell line SUM159R, that is resistant to BRD4 inhibitor JQ1 and cross-resistant to standard chemotherapeutics (doxorubicin) is also highly sensitive to our dual inhibitors, implying their potential use for the treatment of refractory TNBC disease. Excitingly, and for the first time, using a genetic silencing approach (shULK3 in SUM159), we demonstrated that ULK3 is critical for TNBC autophagy and cell survival. As a proof of concept, we reproduced the same genetic silencing experiment in a different cell line, namely WM1366-LC3BmCherry-GFP, an LC3B conveniently engineered system used to visualize proper autophagosome formation and material degradation through autophagy. We verified that both genetic ablation and pharmacologic inhibition of ULK3 are strategies that lead to cancer cell death. Conclusions: In conclusion, we 1) characterized a novel class of dual BRD4/kinase compounds, capable of inhibiting BRD4 activity and autophagy, and superior to the BRD4 inhibitor, JQ1. 2) showed that ULK3 is over-expressed in TNBC. 3) demonstrated that silencing ULK3 blocks autophagy in TNBC cell lines and results in significantly lower cell viability. 4) found that our dual inhibitors present a double bind for TNBC cells that results in increased cytotoxicity and potentially will be useful for the treatment of resistant TNBC. Clinically, we also posit that our dual inhibitors could be easily administered as a single agent, avoiding the potential complication of pharmacokinetics/pharmacodynamics associated with administering multiple therapies.

Citation Format: Marilena Tauro, Tao Li, Conor C Lynch. Dual epigenetic/autophagy inhibition as a novel strategy to tackle triple negative breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD3-10.

Histone deacetylase inhibition prevents the growth of primary and metastatic osteosarcoma

Overall survival rates for patients with advanced osteosarcoma have remained static for over three decades. An in vitro analysis of osteosarcoma cell lines for sensitivity to an array of approved cancer therapies revealed that panobinostat, a broad spectrum histone deacetalyase (HDAC) inhibitor, is highly effective at triggering osteosarcoma cell death. Using in vivo models of orthotopic and metastatic osteosarcoma, here we report that panobinostat impairs the growth of primary osteosarcoma in bone and spontaneous metastasis to the lung, the most common site of metastasis for this disease. Further, pretreatment of mice with panobinostat prior to tail vein inoculation of osteosarcoma prevents the seeding and growth of lung metastases. Additionally, panobinostat impaired the growth of established lung metastases and improved overall survival, and these effects were also manifest in the lung metastatic SAOS2-LM7 model. Mechanistically, the efficacy of panobinostat was linked to high expression of HDAC1 and HDAC2 in osteosarcoma, and silencing of HDAC1 and 2 greatly reduced osteosarcoma growth in vitro. In accordance with these findings, treatment with the HDAC1/2 selective inhibitor romidepsin compromised the growth of osteosarcoma in vitro and in vivo. Analysis of patient-derived xenograft osteosarcoma cell lines further demonstrated the sensitivity of the disease to panobinostat or romidepsin. Collectively, these studies provide rationale for clinical trials in osteosarcoma patients using the approved therapies panobinostat or romidepsin.

Selective inhibition of matrix metalloproteinase-2 in the multiple myeloma-bone microenvironment

Multiple myeloma is a plasma cell malignancy that homes aberrantly to bone causing extensive skeletal destruction. Despite the development of novel therapeutic agents that have significantly improved overall survival, multiple myeloma remains an incurable disease. Matrix metalloproteinase-2 (MMP-2) is associated with cancer and is significantly overexpressed in the bone marrow of myeloma patients. These data provide rationale for selectively inhibiting MMP-2 activity as a multiple myeloma treatment strategy. Given that MMP-2 is systemically expressed, we used novel “bone-seeking” bisphosphonate based MMP-2 specific inhibitors (BMMPIs) to target the skeletal tissue thereby circumventing potential off-target effects of MMP-2 inhibition outside the bone marrow-tumor microenvironment. Using in vivo models of multiple myeloma (5TGM1, U266), we examined the impact of MMP-2 inhibition on disease progression using BMMPIs. Our data demonstrate that BMMPIs can decrease multiple myeloma burden and protect against cancer-induced osteolysis. Additionally, we have shown that MMP-2 can be specifically inhibited in the multiple myeloma-bone microenvironment, underscoring the feasibility of developing targeted and tissue selective MMP inhibitors. Given the well-tolerated nature of bisphosphonates in humans, we anticipate that BMMPIs could be rapidly translated to the clinical setting for the treatment of multiple myeloma.

Abstract P3-06-02: Tackling bone metastatic breast cancer growth with novel bone-seeking matrix metalloproteinase-2 inhibitors

Background. Despite medical advances, currently there is no treatment for breast to bone metastasis. The progression of bone metastatic breast cancer is critically dependent on interactions with the surrounding microenvironment. Therefore, identifying the underpinning molecular mechanisms is vital for the development of new therapies.

Rationale. Gene expression analysis and validation in human and murine specimens of bone metastases revealed matrix metalloproteinases, such as MMP-2, are highly expressed in the bone metastatic microenvironment. Genetic ablation of MMP-2 demonstrated the importance of this MMP in driving the growth of the osteolytic bone metastatic breast cancer by regulating the bioavailability of transforming growth factor β (TGFβ). These data support the rationale for the development of a highly specific MMP-2 inhibitor for the eradication of active bone metastatic breast cancer.

Methods. We utilized a novel chemical approach to synthesize bone seeking MMP inhibitors (BMMPIs) on a bisphosphonic backbone, with specificity for MMP-2 in the nanomolar range (IC50=140 nM).

In vitro, we tested the effect of BMMPIs at varying doses (1nM-100μM) on the viability of the major cellular components of the cancer-bone microenvironment, namely breast cancer cells (PyMT, 4T1), osteoblasts (MC3T3) and osteoclasts (primary monocytes and RAW 264.7). In vivo, mice were intratibially inoculated with either luciferase expressing 4T1 or PyMT (1x105) cells. Mice (n=10/group) then received vehicle, zoledronate (1 mg/kg) or BMMPIs (1 mg/kg). Tumor growth was determined via luminescence quantitation. Cancer induced bone disease was measured ex vivo by μCT, Xray and histomorphometry. MMP activity in vivo and ex vivo was determined via specific activatable MMP probes. Pharmacokinetic and pharmacodynamic studies were performed. Plasma and bone marrow supernatants were collected from PyMT-R221A tumor bearing mice treated with ML115 (5mg/Kg) at 0.25, 0.5, 1, 2, 4, 8, 24 hours and three weeks (n=3 mice/time point).

Currently, we are investigating the BMMPIs ability to impact the metastatic process through an in vivo model of intracardiac inoculation.

Results. BMMPIs significantly impacted the viability of breast cancer cells and osteoclasts in vitro (p<0.05) compared to control. In vivo, BMMPIs significantly reduced the growth of bone metastatic breast cancer compared to control and the standard of care bisphosphonate, zoledronate. MMP activity was also lower in the BMMPI treated groups (using tumor burden to normalize values). μCT/Xray/Histomorphometry analysis also illustrated the significant beneficial effects of the BMMPIs in reducing the size of osteolytic lesions (up to 80% by μCT; p<0.05).

ML115 is rapidly cleared from the plasma and accumulates selectively in the bone marrow microenvironment over time.

Conclusions. MMP-2 specific BMMPIs prevent bone metastatic breast cancer growth by impacting cancer cell viability and cancer induced osteolysis. Given that bisphosphonates are well tolerated in the clinical setting, we predict that BMMPIs could be translated to the clinical setting for the treatment and eradication of bone metastatic breast cancer.

Citation Format: Tauro M, Laghezza A, Tortorella P, Soliman HH, Lynch CC. Tackling bone metastatic breast cancer growth with novel bone-seeking matrix metalloproteinase-2 inhibitors [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-06-02.

Potent Dual BET Bromodomain-Kinase Inhibitors as Value-Added Multitargeted Chemical Probes and Cancer Therapeutics

Synergistic action of kinase and BET bromodomain inhibitors in cell killing has been reported for a variety of cancers. Using the chemical scaffold of the JAK2 inhibitor TG101348, we developed and characterized single agents which potently and simultaneously inhibit BRD4 and a specific set of oncogenic tyrosine kinases including JAK2, FLT3, RET, and ROS1. Lead compounds showed on-target inhibition in several blood cancer cell lines and were highly efficacious at inhibiting the growth of hematopoietic progenitor cells from patients with myeloproliferative neoplasm. Screening across 931 cancer cell lines revealed differential growth inhibitory potential with highest activity against bone and blood cancers and greatly enhanced activity over the single BET inhibitor JQ1. Gene drug sensitivity analyses and drug combination studies indicate synergism of BRD4 and kinase inhibition as a plausible reason for the superior potency in cell killing. Combined, our findings indicate promising potential of these agents as novel chemical probes and cancer therapeutics. Mol Cancer Ther; 16(6); 1054-67. ©2017 AACR.

Abstract P6-12-10: Bone seeking matrix metalloproteinase-2 inhibitors prevent bone metastatic breast cancer growth

Bone metastasis is a common event during breast cancer progression. The resultant lesions are painful and currently, despite medical advances, are incurable. The progression of bone metastatic breast cancer is critically dependent on interactions with the surrounding microenvironment. Therefore, identifying the underpinning molecular mechanisms is vital for the development of new therapies.

Rationale: Gene expression analysis and validation in human and murine specimens of bone metastases revealed that matrix metalloproteinases, such as MMP-2, are highly expressed in the bone metastatic microenvironment and significantly associated with aggressive breast cancer and poorer overall survival. In bone, tumor or host derived MMP-2 contributes to breast cancer growth and does so by processing substrates including type I collagen and transforming growth factor beta (TGFβ) latency proteins. These data provide strong rationale for the application of MMP-2 inhibitors to treat the disease. However, in vivo, MMP-2 is systemically expressed. Therefore, to overcome potential toxicities noted with previous broad-spectrum MMP inhibitors (MMPIs), we used highly selective bisphosphonic based MMP-2 inhibitors (BMMPIs) that allowed for specific bone targeting.

Methods: We utilized a novel chemical approach to synthesize bone seeking MMP inhibitors (BMMPIs) on a bisphosphonic backbone, with specificity for MMP-2 in the nanomolar range (IC50=140 nM).

Results: In vitro, we tested the effect of BMMPIs at varying doses (1nM-100μM) on the viability of the major cellular components of the cancer-bone microenvironment, namely breast cancer cells, (PyMT, 4T1, MDA-MB-231, MCF-7), osteoblasts (MC3T3) and osteoclasts (primary monocytes and RAW 264.7). In vivo, we demonstrated using two bone metastatic models (PyMT-R221A-Luc and 4T1-Luc) that BMMPI treatment significantly reduced tumor growth and tumor associated bone destruction. Additionally, BMMPIs are superior in promoting tumor apoptosis compared to the standard of care bisphosphonate, zoledronate. MMP activity was also lower in the BMMPI treated groups (using tumor burden to normalize values). μCT/Xray/Histomorphometry analysis also illustrated the significant beneficial effects of the BMMPIs in reducing the size of osteolytic lesions (up to 80% by μCT; p<0.05). We demonstrated MMP-2 selective inhibition in the bone microenvironment using specific and broad spectrum MMP probes. Further, compared to zoledronate, BMMPI treated mice had significantly lower levels of TGFβ signaling and MMP generated type I collagen carboxy-terminal (ICTP) fragments. Taken together, our data show the feasibility of selective inhibition of MMPs in the bone metastatic breast cancer microenvironment.

Conclusions. MMP-2 specific inhibition was achieved in the bone microenvironment. BMMPIs significantly inhibit breast cancer growth in bone, they are able to induce breast cancer cell apoptosis and prevent cancer induced bone destruction. Given that bisphosphonates are well tolerated in the clinical setting, we predict that BMMPIs could be translated to the clinical setting for the treatment and eradication of bone metastatic breast cancer.

Citation Format: Tauro M, Laghezza A, Tortorella P, Lynch CC. Bone seeking matrix metalloproteinase-2 inhibitors prevent bone metastatic breast cancer growth [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-12-10.

Bone-Seeking Matrix Metalloproteinase-2 Inhibitors Prevent Bone Metastatic Breast Cancer Growth

Bone metastasis is common during breast cancer progression. Matrix metalloproteinase-2 (MMP-2) is significantly associated with aggressive breast cancer and poorer overall survival. In bone, tumor- or host-derived MMP-2 contributes to breast cancer growth and does so by processing substrates, including type I collagen and TGFβ latency proteins. These data provide strong rationale for the application of MMP-2 inhibitors to treat the disease. However, in vivo, MMP-2 is systemically expressed. Therefore, to overcome potential toxicities noted with previous broad-spectrum MMP inhibitors (MMPIs), we used highly selective bisphosphonic-based MMP-2 inhibitors (BMMPIs) that allowed for specific bone targeting. In vitro, BMMPIs affected the viability of breast cancer cell lines and osteoclast precursors, but not osteoblasts. In vivo, we demonstrated using two bone metastatic models (PyMT-R221A and 4T1) that BMMPI treatment significantly reduced tumor growth and tumor-associated bone destruction. In addition, BMMPIs are superior in promoting tumor apoptosis compared with the standard-of-care bisphosphonate, zoledronate. We demonstrated MMP-2-selective inhibition in the bone microenvironment using specific and broad-spectrum MMP probes. Furthermore, compared with zoledronate, BMMPI-treated mice had significantly lower levels of TGFβ signaling and MMP-generated type I collagen carboxy-terminal fragments. Taken together, our data show the feasibility of selective inhibition of MMPs in the bone metastatic breast cancer microenvironment. We posit that BMMPIs could be easily translated to the clinical setting for the treatment of bone metastases given the well-tolerated nature of bisphosphonates. Mol Cancer Ther; 16(3); 494-505. ©2017 AACR.

Catechol-based matrix metalloproteinase inhibitors with additional antioxidative activity

New catechol-containing chemical entities have been investigated as matrix metalloproteinase inhibitors as well as antioxidant molecules. The combination of the two properties could represent a useful feature due to the potential application in all the pathological processes characterized by increased proteolytic activity and radical oxygen species (ROS) production, such as inflammation and photoaging. A series of catechol-based molecules were synthesized and tested for both proteolytic and oxidative inhibitory activity, and the detailed binding mode was assessed by crystal structure determination of the complex between a catechol derivative and the matrix metalloproteinase-8. Surprisingly, X-ray structure reveals that the catechol oxygens do not coordinates the zinc atom.

Abstract P6-16-02: Treatment of skeletal metastatic breast cancer with bone seeking matrix metalloproteinase inhibitors

Background. Breast to bone metastasis is a common event during breast cancer progression. The resultant lesions are painful and currently, despite medical advances, are incurable. The progression of bone metastatic breast cancer is critically dependent on interactions with the surrounding microenvironment. Therefore, identifying the underpinning molecular mechanisms is vital for the development of new therapies.

Rationale. Gene expression analysis and validation in human and murine specimens of bone metastases revealed matrix metalloproteinases, such as MMP-2, are highly expressed in the bone metastatic microenvironment. Genetic ablation of MMP-2 demonstrated the importance of this MMP in driving the growth of the osteolytic bone metastatic breast cancer by regulating the bioavailability of transforming growth factor β (TGFβ). These data support the rationale for the development of a highly specific MMP-2 inhibitor for the eradication of active bone metastatic breast cancer.

Methods. Given that previous broad-spectrum MMP inhibitor (MMPI) trials were unsuccessful due to dose limiting systemic side effects, we utilized a novel chemical approach to synthesize bone seeking MMP inhibitors (BMMPIs) on a bisphosphonic backbone, with specificity for MMP-2 in the nanomolar range (IC50=140 nM). In vitro, we tested the effect of BMMPIs at varying doses (1nM-100μM) on the viability of the major cellular components of the cancer-bone microenvironment, namely breast cancer cells (PyMT, 4T1), osteoblasts (MC3T3) and osteoclasts (primary monocytes and RAW 264.7). In vivo, mice were intratibially inoculated with either luciferase expressing 4T1 or PyMT (1x105) cells. Mice (n=10/group) then received vehicle, zoledronate (1 mg/kg) or BMMPIs (1 mg/kg). Tumor growth was determined via luminescence quantitation. Cancer induced bone disease was measured ex vivo by μCT, Xray and histomorphometry. MMP activity in vivo and ex vivo was determined via specific activatable MMP probes.

Results. BMMPIs significantly impacted the viability of breast cancer cells and osteoclasts in vitro (p<0.05) compared to control. In vivo BMMPIs significantly reduced the growth of bone metastatic breast cancer compared to control and the standard of care bisphosphonate, zoledronate. MMP activity was also lower in the BMMPI treated groups (using tumor burden to normalize values). μCT/Xray/Histomorphometry analysis also illustrated the significant beneficial effects of the BMMPIs in reducing the size of osteolytic lesions (up to 80% by μCT; p<0.05).

Conclusions. MMP-2 specific BMMPIs prevent bone metastatic breast cancer growth by impacting cancer cell viability and cancer induced osteolysis. Given that bisphosphonates are well tolerated in the clinical setting, we predict that BMMPIs could be translated to the clinical setting for the treatment and eradication of bone metastatic breast cancer.

Citation Format: Tauro M, Laghezza A, Tortorella P, Lynch CC. Treatment of skeletal metastatic breast cancer with bone seeking matrix metalloproteinase inhibitors. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-16-02.

Abstract 398: Specific skeletal targeting of MMP-2 inhibitors for the treatment of bone metastatic breast cancer

Background. Bone metastatic breast cancer promotes extensive bone destruction/osteolysis and is currently incurable. Progression of the disease is critically dependent on cancer-bone interaction. Defining the molecular mechanisms underlying this communication can lead to the identification of new therapeutic targets that will eradicate the disease.

Rationale. Gene expression analysis and validation in human and murine specimens of bone metastases revealed that matrix metalloproteinases (MMPs) such as MMP-2 are highly expressed in the bone metastatic microenvironment. Genetic ablation of MMP-2 highlighted the importance of this MMP in driving the growth of the osteolytic breast cancer lesions. We subsequently found that MMP-2 regulation of transforming growth factor β (TGF β) bioavailability was a major mechanism through which MMP-2 mediated this effect. These data support the rationale for the development of selective MMP inhibitors and imply that MMP-2 inhibition would be a successful strategy for the eradication of active bone metastatic breast cancer.

Methods. To address systemic dose limiting side effects noted in previous broad spectrum MMP inhibitor trials, we utilized a novel chemical approach to generate bone-targeting, highly selective MMP-2 inhibitors grafted onto a bisphosphonic backbone. In vitro, we tested the effect of BMMPIs at varying doses (1nM-100μM) on the viability of the major cellular components of the cancer-bone microenvironment, namely breast cancer cells (PyMT, 4T1), osteoblasts (MC3T3) and osteoclasts (primary monocytes and RAW 264.7). In vivo, mice were inoculated with either luciferase expressing 4T1 or PyMT (100,000) cells. Mice (n = 10/group) then received vehicle, zoledronate (1 mg/kg) or BMMPIs (1 mg/kg). Tumor growth was determined via luminescence quantitation. Cancer induced bone disease was measured ex vivo by μCT, Xray and histomorphometry. MMP activity in vivo and ex vivo was determined via an activatable MMP probe.

Results. BMMPIs significantly impacted the viability of breast cancer cells and osteoclasts in vitro (p<0.05) compared to control. In vivo BMMPIs significantly reduced the growth of bone metastatic breast cancer compared to control and the standard of care bisphosphonate, zoledronate. MMP activity was also lower in the BMMPI treated groups (using tumor burden to normalize values). μCT/Xray/Histomorphometry analysis also illustrated the significant beneficial effects of the BMMPIs in reducing the size of osteolytic lesions (up to 80% by μCT; p<0.05).

Conclusions. MMP-2 specific BMMPIs prevent bone metastatic breast cancer growth by impacting cancer cell viability and cancer induced osteolysis. Given that bisphosphonates are well tolerated in the clinical setting, we predict that BMMPIs could be translated to the clinical setting for the treatment and eradication of bone metastatic breast cancer.

Citation Format: Marilena Tauro, Antonio Laghezza, Paolo Tortorella, Conor C. Lynch. Specific skeletal targeting of MMP-2 inhibitors for the treatment of bone metastatic breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 398. doi:10.1158/1538-7445.AM2015-398

Abstract 4858: A novel strategy for the selective and tissue specific inhibition of MMPs in active breast cancer to bone metastases

Bone metastasis is a common event during breast cancer progression: The delicate balance between bone matrix synthesizing osteoblasts and bone resorbing osteoclasts activities is typically subverted by the presence of tumor cells at the bone site. The resulting incurable lesions cause extensive osteolysis and severely impact the patient's quality of life. Understanding how active breast-to-bone metastases manipulate the bone microenvironment is critical for the development of new therapies to treat the disease. We have recently shown in preclinical animal models of breast to bone metastases that MMP-2 proteolytic activity is critical for the growth of the tumor and the associated osteolysis. We therefore hypothesized that the selective inhibition of MMP-2 at the tumor site would be a potent means through which to prevent the progression of the malignancy. Given that previous broad-spectrum MMP inhibitor (MMPI) trials were unsuccessful mainly because of consistent side effects, we took a novel chemical approach to generate a selective MMPI that would preferentially target the skeleton. To this end, we utilized a bisphosphonate backbone (tiludronate) to synthesize an MMPI (BMMPI) with high specificity for MMP-2 (IC50 0.14± 0.04μM). To test the efficacy of the BMMPI in vivo, we inoculated 6-week old immunocompromized female mice with a luciferase expressing osteolytic breast cancer cell line, PyMT-Luc (105 cells). Following tumor injection, mice (n=6/group) received saline, tiludronate (25mg/kg, to control for bisphosphonate effects) or BMMPI (25mg/kg) sub-cutaneously, twice weekly. Tumor growth was measured by quantitating luminescence over time. Our results show that application of the BMMPI significantly reduced the breast cancer growth over a two-week period (p<0.05). Furthermore, using Faxitron analysis to determine the extent of tumor induced bone destruction, we observed significantly less osteolysis in the tibia images of BMMPI treated mice compared to the control group. Our initial studies also suggest that BMMPIs perform better than clinically used bisphosphonates such as tiludronate. We are currently following up our in vivo/ex vivo analyses with histomorphometrical and histology approaches. In conclusion, our data thus far demonstrate that an MMP-2 specific BMMPI may be an effective means to prevent the progression of breast to bone metastases while at the same time eliminating some of the noted off-target effects of broad-spectrum MMP inhibitors. Since bisphosphonates are well tolerated in the clinical setting, we predict that BMMPIs could be rapidly translated to the patient.

Citation Format: Marilena Tauro, Antonio Laghezza, Paolo Tortorella, Conor C. Lynch. A novel strategy for the selective and tissue specific inhibition of MMPs in active breast cancer to bone metastases. [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 4858. doi:10.1158/1538-7445.AM2014-4858

Arylamino methylene bisphosphonate derivatives as bone seeking matrix metalloproteinase inhibitors

The complexity of matrix metalloproteinase inhibitors (MMPIs) design derives from the difficulty in carefully addressing their inhibitory activity towards the MMP isoforms involved in many pathological conditions. In particular, specific metalloproteinases, such as MMP-2 and MMP-9, are key regulators of the 'vicious cycle' occurring between tumor metastases growth and bone remodeling. In an attempt to devise new approaches to selective inhibitor derivatives, we describe novel bisphosphonate bone seeking MMP inhibitors (BP-MMPIs), capable to be selectively targeted and to overcome undesired side effects of broad spectrum MMPIs. In vitro activity (IC50 values) for each inhibitor was determined against MMP-2, -8, -9 and -14, because of their relevant role in skeletal development and renewal. The results show that BP-MMPIs reached IC50 values of enzymatic inhibition in the low micromolar range. Computational studies, used to rationalize some trends in the observed inhibitory profiles, suggest a possible differential binding mode in MMP-2 that explains the selective inhibition of this isoform. In addition, survival assay was conducted on J774 cell line, a well known model system used to evaluate the structure-activity relationship of BPs for inhibiting bone resorption. The resulting data, confirming the specific activity of BP-MMPIs, and their additional proved propensity to bind hydroxyapatite powder in vitro, suggest a potential use of BP-MMPIs in skeletal malignancies.

Abstract 2134: Bone-targeted MMP inhibitors for the treatment of multiple myeloma

Multiple Myeloma (MM) is a plasma cell malignancy that is hallmarked by areas of extensive bone destruction. Our group, and others have recently shown that individual host or tumor derived MMP-2 and MMP-9 play an important role in the progression of many cancers in the bone microenvironment, including MM. These data support the design of selective inhibitors of individual MMPs for the treatment of multiple myeloma. Previous clinical trials with broad-spectrum matrix metalloproteinase (MMP) inhibitors failed, arguably because the precise roles of individual MMPs had not been fully appreciated. Therefore, in the current study, we have developed novel bone seeking MMP inhibitors (BMMPIs) that are highly selective to MMP-2 and structurally are based on the bone targeting bisphosphonate, Tiludronate. In vitro, BMMPIs showed greater enzyme inhibition, and specificity for MMP-2 than previously synthesized bisphosphonates (e.g. Zoledronate, Etidronate and Tiludronate) with Ki values in the nanomolar range. Further treatment of the 5TGM1 mouse MM cell line with low micromolar concentrations of the BMMPI inhibitors significantly reduced cell viability through inhibition of cell growth (p<0.05). In vivo, 5TGMI tumor-bearing mice receiving BMMP inhibitors three times a week, showed significant increase in overall survival compared to vehicle and tiludronate treated mice over 80 days (p<0.05). This was associated with a reduction in tumor burden and protection from tumor-associated bone loss compared to vehicle treated mice as measured by x-ray and histomorphometry. These data suggest that given the roles for MMPs in tumor progression in bone, that our novel BMMPIs may be effective in the treatment of MM. We predict that MMP-2 specific BMMPIs may be more effective than current clinically used bisphosphonates for the treatment of MM, and may eliminate undesirable side effects of broad-spectrum MMP inhibitors due to their high specificity and bone seeking nature. We are currently continuing to characterize these BMMPI both as single agents, and in combination with existing MM treatments (eg. Bortezomib) for the treatment and eradication of MM.

Citation Format: Gemma Shay, Marilena Tauro, Antonio Laghezza, Paolo Tortorella, Lori A. Hazlehurst, Conor C. Lynch. Bone-targeted MMP inhibitors for the treatment of multiple myeloma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2134. doi:10.1158/1538-7445.AM2013-2134

Hematopoietic stem cell transplantation in Oman

Hematopoietic SCT (HSCT) is an integral part of the management of patients with hematologic disorders. The Sultanate of Oman, with a population of 2.3 million, has an HSCT program based in the Sultan Qaboos University (SQU) hospital. Initiated in 1995, this two-bed unit continues to be the only program in the country. Between June 1995 and August 2006, a total of 128 patients underwent HSCT in this center, averaging about 10-12 transplants per year. The median age of these patients was 11 years (2 months to 45 years). Hematologic malignancies (49%) and inherited disorders (42%) constituted the major transplant indications, whereas BM failure accounted for the remaining. The majority of transplants carried out so far have been HLA-matched sibling-donor allogeneic HSCTs. Among the inherited disorders, homozygous beta-thalassemia and primary immunodeficiency are important transplant indications in this center. The approximate cost of an uncomplicated transplant in this center is US$50,000. The success of this program has now led to the initiation of a new and larger HSCT complex to provide the opportunity for more patients to benefit from this treatment modality within the country.