Journal of Pharmacology and Experimental Therapeutics CHEMOTHERAPY, ANTIBIOTICS, AND GENE THERAPY

[CHEMOTHERAPY, ANTIBIOTICS, AND GENE THERAPY] Tumor-Penetrating Microparticles for Intraperitoneal Therapy of Ovarian Cancer

Lu, Z., Tsai, M., Lu, D., Wang, J., Wientjes, M. G., Au, J. L.-S. — 2008-11-12

Intraperitoneal chemotherapy prolongs survival of ovarian cancer patients, but its utility is limited by treatment-related complications and inadequate drug penetration in larger tumors. Previous intraperitoneal therapy used the paclitaxel/Cremophor EL (polyethoxylated castor oil) formulation designed for intravenous use. The present report describes the development of paclitaxel-loaded microparticles designed for intraperitoneal treatment (referred to as tumor-penetrating microparticles or TPM). Evaluation of TPM was performed using intraperitoneal metastatic, human ovarian SKOV3 xenograft tumor models in mice. TPM were retained in the peritoneal cavity and adhered to tumor surface. TPM consisted of two biocompatible and biodegradable polymeric components with different drug release rates; one component released the drug load rapidly to induce tumor priming, whereas the second component provided sustained drug release. Tumor priming, by expanding interstitial space, promoted transport and penetration of particulates in tumors. These combined features resulted in the following advantages over paclitaxel/Cremophor EL: greater tumor targeting (16-times higher and more sustained concentration in omental tumors), lower toxicity to intestinal crypts and less body weight loss, greater therapeutic efficacy (longer survival and higher cure rate), and greater convenience (less frequent dosing). TPM may overcome the toxicities and compliance-related problems that have limited the utility of intraperitoneal therapy.

[CHEMOTHERAPY, ANTIBIOTICS, AND GENE THERAPY] Chemotherapy-Induced CXC-Chemokine/CXC-Chemokine Receptor Signaling in Metastatic Prostate Cancer Cells Confers Resistance to Oxaliplatin through Potentiation of Nuclear Factor-{kappa}B Transcription and Evasion of Apoptosis

2008-11-12

Constitutive activation of nuclear factor (NF)-B is linked with the intrinsic resistance of androgen-independent prostate cancer (AIPC) to cytotoxic chemotherapy. Interleukin-8 (CXCL8) is a transcriptional target of NF-B whose expression is elevated in AIPC. This study sought to determine the significance of CXCL8 signaling in regulating the response of AIPC cells to oxaliplatin, a drug whose activity is reportedly sensitive to NF-B activity. Administration of oxaliplatin to PC3 and DU145 cells increased NF-B activity, promoting antiapoptotic gene transcription. In addition, oxaliplatin increased the transcription and secretion of CXCL8 and the related CXC-chemokine CXCL1 and increased the transcription and expression of CXC-chemokine receptors, especially CXC-chemokine receptor (CXCR) 2, which transduces the biological effects of CXCL8 and CXCL1. Stimulation of AIPC cells with CXCL8 potentiated NF-B activation in AIPC cells, increasing the transcription and expression of NF-B-regulated antiapoptotic genes of the Bcl-2 and IAP families. Coadministration of a CXCR2-selective antagonist, AZ10397767 (Bioorg Med Chem Lett 18:798–803, 2008), attenuated oxaliplatin-induced NF-B activation, increased oxaliplatin cytotoxicity, and potentiated oxaliplatin-induced apoptosis in AIPC cells. Pharmacological inhibition of NF-BorRNA interference-mediated suppression of Bcl-2 and survivin was also shown to sensitize AIPC cells to oxaliplatin. Our results further support NF-B activity as an important determinant of cancer cell sensitivity to oxaliplatin and identify the induction of autocrine CXCR2 signaling as a novel mode of resistance to this drug.

[CHEMOTHERAPY, ANTIBIOTICS, AND GENE THERAPY] Impact of High and Low Folate Diets on Tissue Folate Receptor Levels and Antitumor Responses Toward Folate-Drug Conjugates

2008-11-12

Herein, we present a detailed analysis on the effects of feeding laboratory mice both high and low folic acid (folate)-containing diets as related to associated changes in serum and red blood cell (RBC) folate levels, tissue-derived folate receptor levels, and the ability of folate-drug conjugates to bind and effectuate activity against folate receptor (FR)-positive tumor xenografts. Our data show that serum and RBC folate concentrations sharply drop immediately after mice are switched to low folate diets; however, both parameters reach steady-state, "human-like" levels after 6 weeks. Interestingly, tissue-related folate binding capacities were also lowered during the dietary modulation period, whereas the net uptake of a radiolabeled folate conjugate was simultaneously increased 2.6- and 5-fold in FR-positive kidney and tumor tissue, respectively. Finally, the performances of several clinically and preclinically relevant folate-drug conjugates were evaluated against tumors in mice that were fed high or low folate diets. Except when administered at a dose level 6-fold less than that required to saturate endogenous FRs, no significant loss of antitumor activity was observed. From these findings, we conclude that lowering the dietary intake of folates in mice has little impact on the biological activity of repetitively dosed folate-targeted agents but that low folate diet regimens will reduce serum and RBC folate levels down to levels that more closely approximate the normal human ranges.

[CHEMOTHERAPY, ANTIBIOTICS, AND GENE THERAPY] Enhancement of Cisplatin [cis-Diammine Dichloroplatinum (II)] Cytotoxicity by O6-Benzylguanine Involves Endoplasmic Reticulum Stress

2008-10-17

O⁶-Benzylguanine (BG) enhances cisplatin [cis-diammine dichloroplatinum (II)]-induced cytotoxicity and apoptosis in head and neck cancer cell lines by an unknown mechanism. We investigated the effect of cisplatin with and without BG on two targets of damage: DNA and the endoplasmic reticulum (ER). We chose three cancer cell lines to ascertain the mechanism of BG-enhanced cytotoxicity: SQ20b head and neck and SKOV-3x ovarian cancer cell lines, where BG enhanced cisplatin cytotoxicity, and A549 nonsmall cell lung cancer line, where BG did not enhance cisplatin cytotoxicity. All three lines had an increase in DNA damage when BG was added to cisplatin treatment, as evidenced by increased platination and phosphorylated histone H2AX formation. The increase in cisplatin-induced DNA damage after treatment with BG plus cisplatin is not sufficient to increase cytotoxicity or apoptosis in A549 cells. We evaluated the effect of cisplatin on the ER and observed increased caspase 12 cleavage in SQ20b and SKOV-3x cells, but not in A549 cells, after treatment with BG plus cisplatin versus cisplatin alone. Growth arrest and DNA damage inducible (GADD) 153, an ER stress-response gene, is up-regulated after treatment with BG plus cisplatin compared with cisplatin alone in SQ20b and SKOV-3x cells, but not in A549 cells. ER stress-induced apoptosis is an integral part of the mechanism by which BG enhances cisplatin. Inhibition of ER stress in the SQ20b cell line by salubrinal, an inhibitor of eIF2 dephosphorylation, or GADD153 small interfering RNA, abrogated BG-enhancement of cisplatin cytotoxicity and apoptosis through caspase 3 and 12 cleavage. These data indicate GADD153 up-regulation plays an important role in BG-enhanced cisplatin cytotoxicity and apoptosis.