A case study of personalized therapy for osteosarcoma.

BACKGROUND: Effective targeted therapies are needed in sarcomas, but the biological heterogeneity of these tumors has presented a challenge to clinical integration of small molecule inhibitors in sarcoma treatment. Here we outline a process to personalize therapy for sarcomas through a case study of a canine with spontaneous osteosarcoma. PROCEDURE: Rapid establishment of a primary tumor cell culture is described, followed by efficient functional characterization of the tumor that identified the Src inhibitor dasatinib as the most effective targeted therapy for this individual dog. RESULTS: Adjuvant dasatinib was administered for a total of 26 weeks following treatment with chemotherapy. Pharmacokinetic studies confirm that a therapeutic serum concentration was achieved at a tolerable dose of 0.75 mg/kg/day. The canine patient remains without evidence of recurrent disease 24 months following initial diagnosis. CONCLUSIONS: The approach described through this illustrative case study is broadly applicable and might be used for other solid tumors in canines as well as in humans.

The effects of taurolidine alone and in combination with doxorubicin or carboplatin in canine osteosarcoma in vitro.

BACKGROUND: Osteosarcoma (OS) affects over 8000 dogs/year in the United States. The disease usually arises in the appendicular skeleton and metastasizes to the lung. Dogs with localized appendicular disease benefit from limb amputation and chemotherapy but most die within 6-12 months despite these treatments. Taurolidine, a derivative of taurine, has anti-tumor and anti-angiogenic effects against a variety of cancers. The following in vitro studies tested taurolidine as a candidate for adjuvant therapy for canine OS. Tests for p53 protein status and caspase activity were used to elucidate mechanisms of taurolidine-induced cell death. RESULTS: Taurolidine was cytotoxic to osteosarcoma cells and increased the toxicity of doxorubicin and carboplatin in vitro. Apoptosis was greatly induced in cells exposed to 125 µM taurolidine and less so in cells exposed to 250 µM taurolidine. Taurolidine cytotoxicity appeared caspase-dependent in one cell line; with apparent mutant p53 protein. This cell line was the most sensitive to single agent taurolidine treatment and had a taurolidine-dependent reduction in accumulated p53 protein suggesting taurolidine's effects may depend on the functional status of p53 in canine OS. CONCLUSION: Taurolidine's cytotoxic effect appears dependent on cell specific factors which may be explained, in part, by the functional status of p53. Taurolidine initiates apoptosis in canine OS cells and this occurs to a greater extent at lower concentrations. Mechanisms of cell death induced by higher concentrations were not elucidated here. Taurolidine combined with doxorubicin or carboplatin can increase the toxicity of these chemotherapy drugs and warrants further investigation in dogs with osteosarcoma.

Pharmacokinetic study and evaluation of the safety of taurolidine for dogs with osteosarcoma.

BACKGROUND: Osteosarcoma in dogs and humans share many similarities and the dog has been described as an excellent model to study this disease. The median survival in dogs has not improved in the last 25 years. Taurolidine has been shown to be cytotoxic to canine and human osteosarcoma in vitro. The goals of this study were to determine the pharmacokinetics and safety of taurolidine in healthy dogs and the safety of taurolidine in combination with doxorubicin or carboplatin in dogs with osteosarcoma. METHODS: Two percent taurolidine was infused into six healthy dogs (150 mg/kg) over a period of two hours and blood samples were taken periodically. One dog received taurolidine with polyvinylpyrrolidone (PVP) as its carrier and later received PVP-free taurolidine as did all other dogs in this study. Serum taurolidine concentrations were determined using high-performance liquid chromatography (HPLC) online coupled to ESI-MS/MS in the multiple reaction monitoring mode. Subsequently, the same dose of taurolidine was infused to seven dogs with osteosarcoma also treated with doxorubicin or carboplatin. RESULTS: Taurolidine infusion was safe in 6 healthy dogs and there were no significant side effects. Maximum taurolidine serum concentrations ranged between 229 to 646 µM. The dog that received taurolidine with PVP had an immediate allergic reaction but recovered fully after the infusion was stopped. Three additional dogs with osteosarcoma received doxorubicin and taurolidine without PVP. Toxicities included dilated cardiomyopathy, protein-losing nephropathy, renal insufficiency and vasculopathy at the injection site. One dog was switched to carboplatin instead of doxorubicin and an additional 4 dogs with osteosarcoma received taurolidine-carboplatin combination. One incidence of ototoxicity occurred with the taurolidine- carboplatin combination. Bone marrow and gastro-intestinal toxicity did not appear increased with taurolidine over doxorubicin or carboplatin alone. CONCLUSIONS: Taurolidine did not substantially exacerbate bone marrow or gastro-intestinal toxicity however, it is possible that taurolidine increased other toxicities of doxorubicin and carboplatin. Administering taurolidine in combination with 30 mg/m2 doxorubicin in dogs is not recommended but taurolidine in combination with carboplatin (300 mg/m2) appears safe.

Quantitation of mercapturic acid conjugates of 4-hydroxy-2-nonenal and 4-oxo-2-nonenal metabolites in a smoking cessation study.

The breakdown of polyunsaturated fatty acids (PUFAs) under conditions of oxidative stress results in the formation of lipid peroxidation (LPO) products. These LPO products such as 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE) can contribute to the development of cardiovascular and neurodegenerative diseases and cancer. Conjugation with glutathione, followed by further metabolism to mercapturic acid (MA) conjugates, can mitigate the effects of these LPO products in disease development by facilitating their excretion from the body. We have developed a quantitative method to simultaneously assess levels of 4-oxo-2-nonen-1-ol (ONO)-MA, HNE-MA, and 1,4-dihydroxy-2-nonene (DHN)-MA in human urine samples utilizing isotope-dilution mass spectrometry. We are also able to detect 4-hydroxy-2-nonenoic acid (HNA)-MA, 4-hydroxy-2-nonenoic acid lactone (HNAL)-MA, and 4-oxo-2-nonenoic acid (ONA)-MA with this method. The detection of ONO-MA and ONA-MA in humans is significant because it demonstrates that HNE/ONE branching occurs in the breakdown of PUFAs and suggests that ONO may contribute to the harmful effects currently associated with HNE. We were able to show significant decreases in HNE-MA, DHN-MA, and total LPO-MA in a group of seven smokers upon smoking cessation. These data demonstrate the value of HNE and ONE metabolites as in vivo markers of oxidative stress.

Tumor imaging using technetium-99m bound to pH-sensitive peptides.

Solid tumors often display metabolic abnormalities that consistently produce low pH in the extracellular space of poorly perfused tissue. These acidic regions may provide a mechanism for drug targeting. Peptides have been designed in such a manner that they exist in an anionic hydrophilic form at the pH of normal tissues, but then undergo a sharp transition to a non-ionic lipophilic form at reduced pH. Peptides were labeled with fluorescein or technetium-99m (99mTc) and evaluated in vitro and in two murine models of cancer. Our studies suggest that PAP-1, an 18 amino acid pH activated peptide with a pH of transition between hydrophilic and lipophilic forms (pT) of 6.4, will deliver fluorescein and 99mTc to tumors. Activation of PAP-1 by low pH and penetration into the plasma membrane of cells and tumors were confirmed using flow cytometry, fluorescence microscopy, and gamma scintigraphy. These results support our central hypothesis that PAP-1 may enable the selective delivery of macromolecules to tumors. This technology has potential for exploiting a common property of tumors to achieve highly specific medical intervention.

Effects of chlorophyllin on transport of dibenzo(a, l)pyrene, 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine, and aflatoxin B(1) across Caco-2 cell monolayers.

Chlorophyllin (CHL) is a sodium copper derivative of chlorophyll that is capable of forming strong non-covalent complexes with several known carcinogens. Antimutagenic and anticarcinogenic effects, including reduced DNA adduct and tumor formation have been demonstrated for CHL against aflatoxin B(1) (AFB(1)), dibenzo(a,l)pyrene (DBP) and 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine (PhIP). Alterations in uptake and/or metabolism of planar molecules with at least partial ring structure have been proposed as mechanisms of action for CHL chemoprevention. The Caco-2 cell model of intestinal epithelial transport was used to evaluate the absorption of 1 microM DBP, AFB(1) and PhIP across cell monolayers in the presence of 0, 1, 10, and 100 microM CHL. No significant differences were observed in the permeability (P(e)) of DBP and AFB(1) from the basolateral-to-apical (BL --> AP) compared to apical-to-basolateral (AP --> BL) compartments for DBP and AFB(1), however, the P(e) of PhIP from BL --> AP, 1.26 x 10(5) +/- 2.10 x 10(6) cm/s, was significantly higher than AP --> BL, 5.83 x 10(6) +/- 7.56 x 10(7) cm/s, (P<0.001) suggesting an active efflux pathway. Transport of DBP from AP --> BL compartments was significantly reduced at all CHL concentrations (P<0.05). AP --> BL transport of AFB(1) was significantly reduced by the addition of 100 microM CHL (P<0.05) while 1 microM or 10 microM CHL had no effect. Complexation studies revealed a higher binding affinity (K(b)) for DBP to CHL compared to AFB(1) to CHL in transport buffer. AP --> BL transport of PhIP, which has a lower binding affinity for CHL than AFB(1) or DBP, was not significantly altered by the addition of CHL. These data suggest that the transport of AFB(1) and DBP can be inhibited by CHL, which supports a model of direct binding in the intestinal tract of CHL to these carcinogens with resultant reduction of bioavailability as one mechanism of action as a cancer chemopreventive agent.

Resistance to chemotherapeutic drugs overcome by c-Myc inhibition in a Lewis lung carcinoma murine model.

Chemotherapy resistance is a significant obstacle in lung cancer therapy, and has been found to frequently correlate with amplification and overexpression of the c-myc oncogene. Earlier studies have shown that c-Myc inhibition alone is not always effective in cancer models. The purpose of this study was to test different dosing regimen, which included commonly used chemotherapeutic drugs in combination with c-Myc inhibition in a Lewis lung syngeneic drug-resistant murine tumor model. Inhibition of c-myc was specifically achieved by using phosphorodiamidate Morpholino oligomer (PMOs), a novel, non-toxic antisense DNA chemistry for inhibition of gene expression by an RNase H-independent mechanism. When administration of cisplatin overlapped with c-myc PMO (AVI-4126) treatment there was no additional effect on tumor growth inhibition compared to cisplatin alone. In contrast, using a dosing regimen in which cisplatin or taxol treatment preceded AVI-4126, a dramatic decrease in tumor growth rate was observed with tumor areas less then 0.5 cm2 in 60% of the animals at the end of the study. This effect was specific to c-Myc inhibition as other antisense PMOs against p21 or Rad51 showed no such effect in combination with chemotherapy. Immunoblot and HPLC-based analysis of tumor lysates at the end of the study confirmed c-Myc inhibition and detection of intact AVI-4126, respectively. In conclusion, AVI-4126 potentiates the efficacy of chemotherapeutic drugs in a manner that is schedule dependent.

c-myc antisense oligonucleotide treatment ameliorates murine ARPKD.

BACKGROUND: Overexpression of c-myc is postulated to play a role in the pathogenesis of polycystic kidney disease (PKD). c-myc expression is increased in all rodent models of PKD that have been examined as well as in human ADPKD. To determine whether overexpression of renal c-myc contributes to renal cyst formation, C57BL/6J-cpk litters (an animal model of ARPKD) were treated with an antisense oligomer (ASO) to c-myc mRNA. METHODS: Injections of 30 microg of a c-myc ASO were given to C57BL/6J-cpk litters on postnatal days 7-20. Control mice received either sham injections or injections of an equal amount of a scrambled ASO. At 20 days, kidney weight, body weight, serum urea nitrogen (SUN), hematocrit, and renal concentration of ASO were determined. In kidney, c-Myc and PCNA protein were assessed by immunoblotting and steady state levels of renal RNA for c-myc, EGF, SGP-2, and histone H4 were assessed by northern blot hybridization. c-Myc and PCNA proteins were localized by immunohistochemistry. RESULTS: Cystic mice treated with the c-myc ASO had a decreased relative kidney weight, improved renal function, and a reduced amount of cystic change compared with sham and scrambled ASO controls. The abnormal expression of several PKD related proteins and mRNAs were partially reversed by c-myc antisense treatment. c-myc staining appeared to be reduced in the noncystic tubules. Treatment with the c-myc ASO did not cause a reduction in hematocrit or total body weight indicating that the beneficial effects were not due to a generalized inhibition of cell proliferation in rapidly growing tissue. CONCLUSIONS: c-Myc appears to play a role in the cystogenesis of cpk-induced murine PKD and antisense targeting the overexpression of c-myc partially ameliorated the renal changes.