Anti-Tumor Activity and Immunotherapeutic Potential of a Bisphosphonate Prodrug.
ABSTRACT: Bisphosphonates have benefits in breast cancer and multiple myeloma patients and have been used with adoptive immunotherapy with ?? T cells expressing V?2?V?2 TCRs. Although treatment with ?? T cells is safe, it has shown limited efficacy. Present bisphosphonates stimulate ?? T cells but were designed to inhibit bone resorption rather than treating cancer and have limited oral absorption, tumor cell entry, and cause bone side effects. The development of phosphate and phosphonate nucleotide prodrugs has led to important drugs for hepatitis C and HIV. Using a similar approach, we synthesized bisphosphonate prodrugs and found that they efficiently limit tumor cell growth. Pivoxil bisphosphonate esters enter cells where esterases convert them to their active acids. The bisphosphonate esters stimulated ?? T cells to secrete TNF-? in response to a variety of tumor cells more efficiently than their corresponding acids. The most active compound, tetrakis-pivaloyloxymethyl 2-(thiazole-2-ylamino)ethylidene-1,1- bisphosphonate (7), specifically expanded ?? T cells and stimulated them to secrete interferon-? and kill tumor cells. In preclinical studies, combination therapy with compound 7 and ?? T cells prolonged survival of mice inoculated with either human bladder cancer or fibrosarcoma cells. Therefore, bisphosphonate prodrugs could enhance the effectiveness of adoptive cancer immunotherapy with ?? T cells.
Project description:Nitrogen-containing bisphosphonates have antitumor activity in certain breast cancer and myeloma patients. However, these drugs have limited oral absorption, tumor cell entry and activity, and cause bone side effects. The potencies of phosphorylated antiviral drugs have been increased by administering them as prodrugs, in which the negative charges on the phosphate moieties are masked to make them lipophilic. We synthesized heterocyclic bisphosphonate (BP) prodrugs in which the phosphonate moieties are derivatized with pivaloyloxymethyl (pivoxil) groups and that lack the hydroxy "bone hook" on the geminal carbon. When the lipophilic BP prodrugs enter tumor cells, they are converted into their active forms by intracellular esterases. The most active BP prodrug, tetrakispivaloyloxymethyl 2-(thiazole-2-ylamino)ethylidene-1,1-bisphosphonate (7), was found to potently inhibit the in?vitro growth of a variety of tumor cell lines, especially hematopoietic cells, at nanomolar concentrations. Consistent with this fact, compound 7 inhibited the prenylation of the RAP1A small GTPase signaling protein at concentrations as low as 1-10?nm. In preclinical studies, 7 slowed the growth of human bladder cancer cells in an immunodeficient mouse model. Thus, 7 is significantly more active than zoledronic acid, the most active FDA-approved BP, and a potential anticancer therapeutic.
Project description:Bisphoshonates are used clinically to treat disorders of calcium metabolism, hypercalcemia and osteoporosis, and malignant bone disease. Although these agents are commonly used in cancer patients and have potential direct anticancer effects, their use for the treatment of extraskeletal disease is limited as a result of poor cellular uptake. We have designed and synthesized bisphosphonamidate prodrugs that undergo intracellular activation to release the corresponding bisphosphonate and require only two enzymatic activation events to unmask multiple negative charges. We demonstrate efficient bisphosphonamidate activation and significant enhancement in anticancer activity of two bisphosphonamidate prodrugs in vitro compared to the parent bisphosphonate. These data suggest a novel approach to optimizing the anticancer activities of commonly used bisphosphonates.
Project description:Bisphosphonates are standard treatments for bone metastases. When given in the adjuvant setting, they reduce breast cancer mortality and recurrence in bone but only among post-menopausal patients. Optimal drug use would require biomarker-based patient selection. Such biomarkers are not yet in clinical use. Based on the similarities in inflammatory responses to bisphosphonates and Toll-like receptor (TLR) agonists, we hypothesized that TLR9 expression may affect bisphosphonate responses in cells. We compared bisphosphonate effects in breast cancer cell lines with low or high TLR9 expression. We discovered that cells with decreased TLR9 expression are significantly more sensitive to the growth-inhibitory effects of bisphosphonates in vitro and in vivo. Furthermore, cancer growth-promoting effects seen with some bisphosphonates in some control shRNA cells were not detected in TLR9 shRNA cells. These differences were not associated with inhibition of Rap1A prenylation or p38 phosphorylation, which are known markers for bisphosphonate activity. However, TLR9 shRNA cells exhibited increased sensitivity to ApppI, a metabolite that accumulates in cells after bisphosphonate treatment. We conclude that decreased TLR9-expression sensitizes breast cancer cells to the growth inhibitory effects of bisphosphonates. Our results suggest that TLR9 should be studied as a potential biomarker for adjuvant bisphosphonate sensitivity among breast cancer patients.
Project description:Eighteen different bisphosphonates, including four clinically used bisphosphonate acids and their phosphoesters, were studied to evaluate how the bisphosphonate structure affects binding to bone. Bisphosphonates with weak bone affinity, such as clodronate, could not bind to hydroxyapatite after the addition of one ester group. Medronate retained its ability to bind after the addition of one ester group, and hydroxy-bisphosphonates could bind even after the addition of two ester groups. Thus, several bisphosphonate esters are clearly bone binding compounds. The following conclusions about bisphosphonate binding emerge: (1) a hydroxyl group in the geminal carbon takes part in the binding process and increases the bisphosphonate's ability to bind to bone; (2) the bisphosphonate's ability to bind decreases when the amount of ester groups increases; and (3) the location of the ester groups affects the bisphosphonate's binding ability.
Project description:Recent clinical trials have shown that bisphosphonate drugs improve breast cancer patient survival independent of their antiresorptive effects on the skeleton. However, because bisphosphonates bind rapidly to bone mineral, the exact mechanisms of their antitumor action, particularly on cells outside of bone, remain unknown. Here, we used real-time intravital two-photon microscopy to show extensive leakage of fluorescent bisphosphonate from the vasculature in 4T1 mouse mammary tumors, where it initially binds to areas of small, granular microcalcifications that are engulfed by tumor-associated macrophages (TAM), but not tumor cells. Importantly, we also observed uptake of radiolabeled bisphosphonate in the primary breast tumor of a patient and showed the resected tumor to be infiltrated with TAMs and to contain similar granular microcalcifications. These data represent the first compelling in vivo evidence that bisphosphonates can target cells in tumors outside the skeleton and that their antitumor activity is likely to be mediated via TAMs.Bisphosphonates are assumed to act solely in bone. However, mouse models and clinical trials show that they have surprising antitumor effects outside bone. We provide unequivocal evidence that bisphosphonates target TAMs, but not tumor cells, to exert their extraskeletal effects, offering a rationale for use in patients with early disease.
Project description:Bisphosphonates are the most commonly prescribed medicines for osteoporosis and skeletal metastases. The drugs have also been shown to reduce cancer progression, but only in certain patient subgroups, suggesting that there is a molecular entity that mediates bisphosphonate action on tumor cells. Using connectivity mapping, we identified human epidermal growth factor receptors (human EGFR or HER) as a potential new molecular entity for bisphosphonate action. Protein thermal shift and cell-free kinase assays, together with computational modeling, demonstrated that N-containing bisphosphonates directly bind to the kinase domain of HER1/2 to cause a global reduction in downstream signaling. By doing so, the drugs kill lung, breast, and colon cancer cells that are driven by activating mutations or overexpression of HER1. Knocking down HER isoforms thus abrogates cell killing by bisphosphonates, establishing complete HER dependence and ruling out a significant role for other receptor tyrosine kinases or the enzyme farnesyl pyrophosphate synthase. Consistent with this finding, colon cancer cells expressing low levels of HER do not respond to bisphosphonates. The results suggest that bisphosphonates can potentially be repurposed for the prevention and therapy of HER family-driven cancers.
Project description:Bisphosphonates are approved for treating malignant bone disease from advanced cancer because they are effective inhibitors of osteoclast-mediated bone resorption. However, there may be a greater role for the use of bisphosphonates than has previously been considered. There is a large body of preclinical evidence showing that bisphosphonates exert a variety of direct and indirect anticancer activities that affect both tumor cells and the surrounding microenvironment, and that stimulate immune reactions. Recent data from clinical trials have shown that adding the bisphosphonate zoledronate to endocrine therapy or chemotherapy improves disease-free survival of patients with endocrine-responsive early breast cancer in a low estrogen environment (that is, following ovarian suppression therapy or in women with established menopause at diagnosis). Adjuvant treatment with the bisphosphonate clodronate also improves disease-free survival in postmenopausal breast cancer. Additionally, zoledronate was found to prolong survival in patients with symptomatic multiple myeloma or other advanced cancers. Here, we present an overview of preclinical and clinical studies that demonstrate anticancer benefits of bisphosphonates, and we discuss potential mechanisms of action that might be responsible for the anticancer activity of bisphosphonates in the clinic.
Project description:Bisphosphonates are generally used to treat bone diseases, such as bone metastasis from cancer. There is evidence that, through the modification of the pharmacokinetics and biodistribution of bisphosphonates by formulating them into nanoparticles, they may be able to treat extraskeletal tumors. However, many previously reported bisphosphonate nanoparticle formulations show extensive premature release of bisphosphonates. Herein, using zoledronate (Zol), a third-generation bisphosphonate, we developed a new Zol nanoparticle formulation (denoted as Zol-NPs) by encapsulating anionic lipid-coated Zol-calcium nanocomplexes into poly(lactic- co-glycolic) acid nanoparticles emulsified with octadecanoic acid-hydrazone-polyethylene glycol (2000), an acid-sensitive cleavable emulsifying agent. The resultant Zol-NPs, about 180 nm in hydrodynamic diameter, show very limited premature release of Zol (i.e., <5% in 48 h in a simulated physiological condition) and enhanced cytotoxicity to both murine cancer cells and macrophages. In a mouse model with orthotopically transplanted mammary tumors, Zol-NPs significantly reduced the distribution of Zol in bones, but increased its distribution in tumors. Importantly, Zol-NPs also significantly inhibited tumor growth, whereas the equivalent dose of free Zol did not. This platform technology may be exploited to treat extraskeletal tumors with bisphosphonates.
Project description:Ultrasound (US) is a non-ionizing pressure wave that can produce mechanical and thermal effects. Bisphosphonates have demonstrated clinical utility in bone metastases treatment. Preclinical studies suggest that bisphosphonates have anticancer activity. However, bisphosphonates exhibit a high affinity for bone mineral, which reduces their bioavailability for tumor cells. Ultrasound has been shown to be effective for drug delivery but in interaction with gas bubbles or encapsulated drugs. We examined the effects of a clinically relevant dose of bisphosphonate zoledronate (ZOL) in combination with US. In a bone metastasis model, mice treated with ZOL+US had osteolytic lesions that were 58% smaller than those of ZOL-treated animals as well as a reduced skeletal tumor burden. In a model of primary tumors, ZOL+US treatment reduced by 42% the tumor volume, compared with ZOL-treated animals. Using a fluorescent bisphosphonate, we demonstrated that US forced the release of bisphosphonate from the bone surface, enabling a continuous impregnation of the bone marrow. Additionally, US forced the penetration of ZOL within tumors, as demonstrated by the intratumoral accumulation of unprenylated Rap1A, a surrogate marker of ZOL antitumor activity. Our findings made US a promising modality to trigger bisphosphonate anticancer activity in bone metastases and in primary tumors.
Project description:Introduction: Bisphosphonates are well known above all for their use in the treatment of osteoporosis. They also play an important role as accompanying therapy for advanced tumour diseases with extensive spread into the skeletal system. Their adjuvant use in the treatment of breast cancer without bony metastases is currently a subject of controversial discussion. The objective of the present evaluation is to describe the use of bisphosphonates in the therapy for breast cancer. We will show how frequently bisphosphonates are used, which bisphosphonates are preferred and what specific features patients under bisphosphonate therapy exhibit. Methods and Materials: The pseudonymous data set from the biobank of the German PATH foundation was used for the evaluation. From the total collective, 2492 patients were selected after consideration of the inclusion and exclusion criteria. The selected patient collective was divided into two groups (with and without bisphosphonate therapy) and the two groups compared with one another with the help of descriptive statistics. Results: 17.5?% of the 2492 patients had prescriptions for a bisphosphonate as part of their therapy. The most frequently administered bisphosphonate was zoledronate. Pathological (induced by tumour therapy) osteoporosis was the most frequently stated indication among the bisphosphonate patients, followed by consumption starting prior to the breast cancer therapy and treatment of bony metastases. Patients under bisphosphonate and antihormonal therapy frequently received an aromatase inhibitor as the active principle in the antihormonal therapy whereas patients under antihormonal therapy but without bisphosphonates more frequently received tamoxifen as active principle. Ten of the 2492 patients reported receiving bisphosphonate therapy as prophylaxis for bony metastases without a documented and approved indication. Use of bisphosphonates in the course of the GAIN, ICE, SUCCESS or, respectively, NATAN trials was reported by 29 of the 2492 patients. Conclusions: In the PATH collective, bisphosphonates were employed above all for the treatment of (tumour therapy-induced) osteoporosis and bony metastases. Off-label use and participation in clinical trials played only a minor role in this patient collective. Against the background of the uncertain data status for the adjuvant use of bisphosphonates, the development (and use) of standardised, validated questionnaires to record the indications for and frequency of use of bisphosphonate therapy is recommended.