Oxaliplatin loaded PLAGA microspheres: design of specific release profiles.

Oxaliplatin loaded PLAGA microspheres have been prepared by solvent extraction process. Parameters affecting the release kinetics in vitro have been studied in order to design specific release profiles suitable for direct intra-tumoral injection. By varying the nature and the relative proportions of different polymers we managed to prepare microspheres with good encapsulation efficiency (75-90%) and four different release profiles: zero order kinetics (type II) and the classical sigmoïd release profile with three different sizes of plateau and burst. These results, if correlated with in vivo activity, are promising to enhance effectiveness of local tumor treatment.

Circulating nerve growth factor level changes during oxaliplatin treatment-induced neurotoxicity in the rat.

BACKGROUND: Oxaliplatin neurotoxicity represents a clinically-relevant problem and its etio-pathogenesis is still unknown. We explored the possible role of some neuronal growth factors ("neurotrophins") during the course of oxaliplatin sensory neuronopathy. MATERIALS AND METHODS: In our rat model two different doses of oxaliplatin were used (2 and 3 mg/kg i.v. twice weekly for 9 times). The neurotoxicity of the treatment was assessed with neurophysiological and pathological methods and serum neurotrophin levels were measured by ELISA. RESULTS: Both oxaliplatin-treated groups showed the neurophysiological and neuropathological changes which mimic the chronic effects of oxaliplatin administration in humans, e.g. reversible sensory impairment due to dorsal root ganglia neuron damage. These changes were associated with a significant and dose-dependent reduction only in the circulating level of nerve growth factor (NGF), which returned to normal values after neurophysiological and pathological recovery. CONCLUSION: This specific association between neurological impairment and NGF modulation indicates that NGF impairment has a role in the neurotoxicity of oxaliplatin.

Anti-Vascular endothelial growth factor treatment augments tumor radiation response under normoxic or hypoxic conditions.

Recent studies in experimental animals have shown that combining antiangiogenic therapy with radiation can enhance tumor response. Whether this enhancement is mainly attributable to angiogenesis inhibition, endothelial cell radiosensitivity, tumor cell apoptosis, or a decrease in the number of hypoxic cells (improved oxygenation) is not known. We designed this study to discern the role of tumor oxygenation. We chose an anti-vascular endothelial growth factor (anti-VEGF) monoclonal antibody (mAb) which has a known target, human VEGF. We also measured interstitial fluid pressure (IFP) to test the hypothesis that the decreased vascular permeability induced by the anti-VEGF mAb can lower IFP. The effect of anti-VEGF mAb on vascular density, partial oxygen tension (pO2), and apoptosis was also measured. Athymic NCr/Sed nu/nu mice bearing 6-mm xenograft of the human glioblastoma multiforme (U87), or colon adenocarcinoma (LS174T) were treated with anti-VEGF mAb injected i.p. on alternate days for a total of six injections at a dosage of 100 microg/injection/mouse. For combined anti-VEGF and radiation, single radiation doses were given under normal blood flow (20 and 30 Gy) or clamped hypoxic conditions (30 and 40 Gy) 24 h after the sixth injection of mAb. The inhibition of the growth of U87 and LS174T tumors by the anti-VEGF mAb was associated with a significant reduction in tumor vascular density and a relatively small increase in the number of apoptotic cells. Compared with size-matched controls, IFP decreased by 74% in LS174T, and 73% in U87 in mice treated with anti-VEGF mAb. After antibody treatment PO2 increased significantly in U87, but did not change in LS174T tumors. Combined treatment induced in U87 tumors a tumor-growth delay (TGD) which was greater than additive; in LS174T except for the 40-Gy hypoxic group, the effect was only additive. In both U87 and LS174T the TGD induced by the antibody was independent of oxygen levels in the tumor at the time of radiation. The fact that the increase in TGD occurred under both normoxic and hypoxic conditions suggests that anti-VEGF mAb treatment can compensate for the resistance to radiation induced by hypoxia.

Taxane-induced apoptosis decompresses blood vessels and lowers interstitial fluid pressure in solid tumors: clinical implications.

Elevated tumor interstitial fluid pressure (IFP) is partly responsible for the poor penetration and distribution of therapeutic agents in solid tumors. The etiology of tumor interstitial hypertension is poorly understood. We have postulated that the solid stress generated by tumor cells growing in a confined space compresses blood vessels and increases tumor microvascular pressure and IFP. To test the hypothesis that neoplastic cell loss would decompress blood vessels and lower IFP, we induced apoptosis in tumors with paclitaxel and docetaxel. Taxanes inhibited the growth of the murine mammary carcinoma (MCa-IV) and of the human soft tissue sarcoma (HSTS-26T). Taxanes induced apoptosis and reduced the density of intact neoplastic cells in both MCa-IV and HSTS-26T. To determine whether neoplastic cell loss decompressed blood vessels, we measured the diameter of tumor vessels in HSTS-26T tumors implanted in transparent dorsal skin fold chambers. At 48 and 96 h after paclitaxel, the diameter of tumor vessels was significantly increased. The increase in vascular diameters was associated with reductions in microvascular pressure and IFP. The changes in neoplastic cell density and IFP were also correlated. In the human glioblastoma U87, which is resistant to paclitaxel, the IFP and cellular density were not modified by paclitaxel treatment. Collectively, these results support the hypothesis that solid stress generated by neoplastic cell proliferation increases vascular resistance and IFP. The increase in vessel diameter induced by paclitaxel and docetaxel suggests that taxanes could improve tumor response by increasing the vascular surface area for delivery of therapeutic agents.

Evaluation of Taxol in head and neck squamous carcinoma multicellular tumor spheroids.

Taxol cytotoxicity was evaluated in human head and neck squamous carcinoma cell lines growing as multicellular tumor spheroids (MTS) and compared with monolayered culture using conventional clonogenic assays. End points were respectively the concentration inhibiting 50% of the cellular growth (IC50) in clonogenic assays and the concentration required to induce a 50% decrease in the MTS volume (ID50) or number in the overall spheroid population (SCC50). A significant difference was observed when the cells were exposed for 10 days to Taxol as a consequence of the different growth kinetics of the spheroids. After 16 day exposure of spheroids to Taxol, no difference remained between ID50 and IC50. In addition, a significant correlation was found between individual spheroid sensitivity to Taxol (ID50) and the spheroid population sensitivity (SCC50). Both parameters (ID50 and SCC50) defined in cell models appear useful for the evaluation of chemosensitivity of three-dimensional structures known to be closer to in vivo tumor models.

In vitro evaluation of Taxol combined with radiations in human squamous cell carcinoma spheroids.

The effect of Taxol on the radiation sensitivity of human squamous carcinoma of the head and neck region was determined in vitro, using clonogenic assays and multicellular tumor spheroids (MTS). Radiosensitivity parameters were determined by alpha and beta for clonogenic assays, and by the residual/control volume ratios at 2 Gy (RSV2) and the dose inducing 50% decrease in MTS number (SCD50) for spheroids. In HTB43 and CAL27 colonies, the combination was antagonist. In spheroids, Taxol induced a decrease of RSV2 and SCD50 in HTB43 and CAL27 MTS and their combinations with radiation were synergistic and additive, respectively. Therefore, the different results obtained by clonogenic assays and MTS may suggest higher drug incorporation through the multiple cell layers of the spheroids than in monolayers.

Association of docetaxel/paclitaxel with irradiation in ovarian carcinoma cell lines in bidimensional (sulforhodamine B assay) and tridimensional (spheroids) cultures.

The association of taxoid derivatives (paclitaxel and docetaxel) with irradiation was evaluated in ovarian carcinoma cell lines (A2780 and CAVEOC-2) using the multicellular tumor spheroids (MTS) tridimensional model and compared to the conventional bidimensional model. The radiosensitivity parameters were the surviving fraction at 2 Gy, and alpha calculated using the linear-quadratic model for monolayer culture, the residual/control volume ratios at 2 Gy (RSV2) and doses inducing 50% decrease in MTS number (SCD50) calculated for spheroids. In A2780 monolayer culture, the combination was synergistic for paclitaxel and additive for docetaxel. In spheroids, both compounds induced a decrease in RSV2 and SCD50 in the two cell lines, and their combination with radiation was additive. Therefore, the radiosensitizing effect of taxoid derivatives was not constant in ovarian cell lines. The different results achieved in monolayer culture and in spheroids may suggest higher drug incorporation and fixation through the multiple cell layers of the spheroids than in monolayers.