The secreted protein acidic and rich in cysteine (SPARC) is a matricellular glycoprotein that is produced by tumor and/or neighboring stroma. SPARC expression is thought to facilitate the intracellular accumulation of nanoparticle albumin-bound paclitaxel (nab-paclitaxel, abraxane [ABX]). Gene hypermethylation is a common mechanism for loss of SPARC expression in non-small cell lung cancer (NSCLC). We aim to demonstrate the role of SPARC expression as biomarker for treatment selection using ABX in NSCLC and to evaluate the presence of synergistic antitumor effect when a demethylating agent is combined with ABX.
We analyzed the SPARC messenger RNA expression and SPARC gene methylation status in 13 NSCLC cell lines and 22 minimally passaged patient-derived (PD) NSCLC tumors using real-time (RT) polymerase chain reaction. The effect of ABX on tumor growth was compared with cremophor-solubilized paclitaxel (taxol) in severe combined immunodeficiency mice bearing SPARC-positive PD xenografts. The effect of pretreatment with a demethylating agent, 5-Aza-2'-deoxycytidine (DEC) in SPARC-negative tumors was assessed.
SPARC expression was weak to absent in 62% of established NSCLC cell lines and 68% of PD NSCLC tumor xenografts. SPARC expression could be up-regulated/restored by DEC treatment in both SPARC-negative cell lines and PD xenografts in vitro and in vivo. ABX demonstrated better antitumor efficacy than equitoxic dose of taxol in SPARC-expressing xenografts and some SPARC-negative xenografts. At equimolar doses in vitro, there was similar increased cytotoxicity on DEC pretreatment with either ABX or taxol in SPARC-negative cell lines. At equitoxic doses, there was similar additive antitumor activity of DEC with either ABX or taxol in SPARC-negative PD xenografts.
Endogenous SPARC status is somewhat uncorrelated with response to ABX in NSCLC. The greater antitumor effect of ABX compared with equitoxic dose of taxol observed in SPARC-expressing NSCLC tumors can also be seen in some SPARC-negative tumors. DEC pretreatment similarly enhanced antitumor activity with either ABX or taxol in SPARC-negative tumors.
"SPARC is involved in cell-matrix interaction during tissue remodeling and embryonic development. In SPARC-negative NSCLC cells, SPARC gene undergoes promoter region hypermethylation, resulting in loss of expression.20 In SPARC-positive NSCLC, SPARC is selectively synthesized by the peritumoral stromal fibroblasts in the tumor microenvironment, with minimal production by the tumor cells themselves.21 "
[Show abstract][Hide abstract] ABSTRACT: Lung cancer is the leading cause of cancer mortality worldwide in both men and women. Non-small-cell lung cancer (NSCLC) is the most common type of lung cancer, accounting for more than 80% of cases. Paclitaxel has a broad spectrum of activity against various malignancies, including NSCLC. Paclitaxel is poorly soluble in water and thus, until recently, its commercially available preparations contained a non-ionic solvent Cremophor EL®. Cremophor EL® improves the solubility of paclitaxel and allows its intravenous administration. However, certain side-effects associated with paclitaxel, such as hypersensitivity reactions, myelosuppression, and peripheral neuropathy, are known to be worsened by Cremophor®. Nanoparticle albumin-bound paclitaxel ([nab-paclitaxel] ABRAXANE® ABI-007) is a new generation formulation of paclitaxel that obviates the need for Cremophor®, resulting in a safer and faster infusion without requiring the use of premedications to avoid hypersensitivity. Albumin-binding receptor-mediated delivery and lack of sequestering Cremophor® micelles allow higher intratumoral concentration of pharmacologically active paclitaxel. Multiple clinical trials have demonstrated a superior tolerability profile of nab-paclitaxel in comparison to solvent-bound paclitaxel (sb-paclitaxel). A recent Phase III trial compared the effects of weekly nab-paclitaxel in combination with carboplatin versus sb-paclitaxel in combination with carboplatin given every 3 weeks for first line treatment of NSCLC. This trial highlights the weekly nab-paclitaxel combination as an alternate treatment option for NSCLC, with higher response rate in squamous cell NSCLC and longer survival in elderly patients. This review will focus on the properties of nab-paclitaxel and its use in the first line treatment of NSCLC.
International Journal of Nanomedicine 01/2014; 9(1):209-221. DOI:10.2147/IJN.S41770 · 4.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nanoparticle albumin-bound (nab)-paclitaxel, an albumin-stabilized paclitaxel formulation, demonstrates clinical activity when administered in combination with gemcitabine in patients with metastatic pancreatic ductal adenocarcinoma (PDA). The limited availability of patient tissue and exquisite sensitivity of xenografts to chemotherapeutics have limited our ability to address the mechanistic basis of this treatment regimen. Here, we used a mouse model of PDA to show that the coadministration of nab-paclitaxel and gemcitabine uniquely demonstrates evidence of tumor regression. Combination treatment increases intratumoral gemcitabine levels attributable to a marked decrease in the primary gemcitabine metabolizing enzyme, cytidine deaminase. Correspondingly, paclitaxel reduced the levels of cytidine deaminase protein in cultured cells through reactive oxygen species-mediated degradation, resulting in the increased stabilization of gemcitabine. Our findings support the concept that suboptimal intratumoral concentrations of gemcitabine represent a crucial mechanism of therapeutic resistance in PDA and highlight the advantages of genetically engineered mouse models in preclinical therapeutic trials. SIGNIFICANCE: This study provides mechanistic insight into the clinical cooperation observed between gemcitabine and nab-paclitaxel in the treatment of pancreatic cancer.
Cancer Discovery 03/2012; 2(3):260-9. DOI:10.1158/2159-8290.CD-11-0242 · 19.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Anticancer drugs as well as nano-sized drug delivery systems face many barriers that hinder penetration deeply and evenly into solid tumors: a chaotic, tortuous vascular compartment resulting in tumor tissue distant from microvessels, a heterogeneous blood flow distribution with a concomitant defective microcirculatory exchange process, and a high interstitial fluid pressure. Furthermore, a resulting hostile tumor microenvironment characterized by hypoxia and/or extracellular acidosis can reduce the efficacy of anticancer drugs and confer drug resistance. Conversely, the enhanced permeation and retention effect has become the gold standard for developing macromolecular prodrugs and nano-sized drug delivery systems. Preclinically, there are meanwhile numerous in vivo proof-of-concepts that demonstrate not only a better tolerability of nano-sized drug delivery systems but also of enhanced antitumor efficacy compared to the conventional clinical standard. When faced with such a complex and heterogeneous disease as cancer in humans, it is more likely that a tailor-made combination of different therapeutic strategies will achieve the best results. In this respect, combining low-molecular weight cytostatic drugs with nano-sized drug delivery systems appears to be a natural choice for combination therapy that aims at distributing anticancer drugs at higher concentrations in the tumor in a more even manner. To date, such drug delivery approaches have been inadequately explored. In this review, we summarize the state-of-the-art of combination approaches with liposomal doxorubicin (Doxil™), the paclitaxel-albumin nanoparticle (Abraxane™) and the albumin-binding doxorubicin prodrug DOXO-EMCH (INNO-206), and discuss the insights obtained and perspectives for further research in this intriguing and promising field of drug delivery research.
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