Chunjing Wu

South Florida Veterans Affairs Foundation for Research and Education, Miami, Florida, United States

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Publications (9)22.96 Total impact

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    ABSTRACT: Arginine deprivation is a promising strategy for treating ASS-negative malignant tumors including melanoma. However, autophagy can potentially counteract the effectiveness of this treatment by acting as a pro-survival pathway. By combining tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) with arginine deprivation using ADI-PEG20 (pegylated arginine deiminase), we achieved enhanced apoptosis and accelerated cell death in melanoma cell lines. This implies a switch from autophagy to apoptosis. In our current investigation, we found that TRAIL could induce the cleavage of two key autophagic proteins, Beclin-1 and Atg5, in the combination treatment. Using specific inhibitors for individual caspases, we found that caspase-8 inhibitor could completely abolish the cleavage. Furthermore, caspase-8 inhibitor was able to fully reverse the enhanced cytotoxicity induced by TRAIL. Inhibitors for caspase-3, 6, 9, and 10 were able to block the cleavage of these two autophagic proteins to some extent and correspondingly rescue cells from the cytotoxicity of the combination of TRAIL and arginine deprivation. In contrast, calpain inhibitor could not prevent the cleavage of either Beclin-1 or Atg5, and was unable to prevent cell death. Overall, our data indicate that the cleavage of Beclin-1 and Atg5 by TRAIL-initiated caspase activation is one of the mechanisms that lead to the enhancement of the cytotoxicity in the combination treatment.
    Molecular and Cellular Biochemistry 11/2012; · 2.33 Impact Factor
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    ABSTRACT: Elimination of cisplatin-resistant lung cancer cells remains a major obstacle. We have shown that cisplatin-resistant tumors have higher reactive oxygen species (ROS) levels and can be exploited for targeted therapy. Here, we show that increased secretion of the antioxidant thioredoxin-1 (TRX1) resulted in lowered intracellular TRX1 and contributed to higher ROS in cisplatin-resistant tumors in vivo and in vitro. By reconstituting TRX1 protein in cisplatin-resistant cells, we increased sensitivity to cisplatin but decreased sensitivity to elesclomol (ROS inducer). Conversely, decreased TRX1 protein in parental cells reduced the sensitivity to cisplatin but increased sensitivity to elesclomol. Cisplatin-resistant cells had increased endogenous oxygen consumption and mitochondrial activity but decreased lactic acid production. They also exhibited higher levels of argininosuccinate synthetase (ASS) and fumarase mRNA, which contributed to oxidative metabolism (OXMET) when compared with parental cells. Restoring intracellular TRX1 protein in cisplatin-resistant cells resulted in lowering ASS and fumarase mRNAs, which in turn sensitized them to arginine deprivation. Interestingly, cisplatin-resistant cells also had significantly higher basal levels of acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS). Overexpressing TRX1 lowered ACC and FAS proteins expressions in cisplatin-resistant cells. Chemical inhibition and short interfering RNA of ACC resulted in significant cell death in cisplatin-resistant compared with parental cells. Conversely, TRX1 overexpressed cisplatin-resistant cells resisted 5-(tetradecyloxy)-2-furoic acid (TOFA)-induced death. Collectively, lowering TRX1 expression through increased secretion leads cisplatin-resistant cells to higher ROS production and increased dependency on OXMET. These changes raise an intriguing therapeutic potential for future therapy in cisplatin-resistant lung cancer.
    Molecular Cancer Therapeutics 03/2012; 11(3):604-15. · 5.60 Impact Factor
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    ABSTRACT: Current treatment for advanced, metastatic melanoma is not very effective, and new modalities are needed. ADI-PEG20 is a drug that specifically targets ASS-negative malignant melanomas while sparing the ASS-expressing normal cells. Although laboratory research and clinical trials showed promising results, there are some ASS-negative cell lines and patients that can develop resistance to this drug. In this report, we combined ADI-PEG20 with another antitumor drug TRAIL to increase the killing of malignant melanoma cells. This combination can greatly inhibit cell growth (to over 80%) and also enhanced cell death (to over 60%) in four melanoma cell lines tested compared with control. We found that ADI-PEG20 could increase the cell surface receptors DR4/5 for TRAIL and that caspase activity correlated with the increased cell death. These two drugs could also increase the level of Noxa while decrease that of survivin. We propose that these two drugs can complement each other by activating the intrinsic and extrinsic apoptosis pathways, thus enhance the killing of melanoma cells.
    Biochemical and Biophysical Research Communications 03/2010; 394(3):760-6. · 2.41 Impact Factor
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    ABSTRACT: Cisplatin is an important chemotherapeutic agent in lung cancer treatment. The mechanism of drug resistance to cisplatin is complex and historically has been difficult to overcome. We report here that cisplatin resistant lung cancer cell lines possess high basal levels of reactive oxygen species (ROS) when compared to normal cells and their parental cell counterparts. These resistant cells also have low thioredoxin (TRX) levels which may be one of the contributory factors to high ROS. N'(1),N'(3)-dimethyl-N'(1),N'(3)-bis(phenylcarbonothioyl) propanedihydrazide (elesclomol), an agent known to increase ROS is selectively toxic to cisplatin-resistant cells, while sparing normal cells and the parental counterpart. The cytotoxic effect of elesclomol in resistant cells is accompanied by further decreases in TRX and glutathione (GSH) antioxidant systems, while opposite results were found in parental cells. The ID(50) of elesclomol in cisplatin-resistant cells ranged from 5-10 nM, which is well within clinically achievable ranges. N-Acetylcysteine (NAC), which is known to neutralize ROS, can abolish the cytotoxic effect of elesclomol, suggesting that the cytotoxic effect results from increased ROS. Overall, our data suggest that elesclomol selectively kills cisplatin-resistant tumor cells through increased ROS. This agent may hold potential to overcome cisplatin resistance and should be further explored to treat patients who have failed cisplatin therapy.
    Cancers. 01/2009; 1(1):23-38.
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    ABSTRACT: We show that cisplatin resistance in certain lung cancer cell lines can be reversed through inhibition of mTOR (mammalian Target of Rapamycin). These cell lines appear to possess high levels of phospho-mTOR, phospho-AKT and other growth-related proteins, such as hTERT (human telomerase reverse transcriptase), and Cyclin D3 which decrease upon inhibition of mTOR. Interestingly in one cisplatin resistant cell line which expresses BCL2/BCLxL, treatment with mTOR inhibitor (CCI-779) results in decreased levels of these anti-apoptotic proteins and may contribute to increasing apoptosis. Moreover, continuous exposure to CCI-779 was found to increase the expression of the multi-drug resistant P-gp1(P-gycoprotein1) efflux pump and therefore should be taken into consideration when designing clinical trials with this compound.
    European Journal of Pharmacology 07/2008; 591(1-3):124-7. · 2.59 Impact Factor
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    ABSTRACT: It has been shown that melanoma cells do not express argininosuccinate synthetase (ASS) and therefore are unable to synthesize arginine from citrulline. Depleting arginine using pegylated arginine deiminase (ADI-PEG20) results in cell death in melanoma but not normal cells. This concept was translated into clinical trial and responses were seen. However, induction of ASS expression does occur which results in resistance to ADI-PEG20. We have used 4 melanoma cell lines to study factors which may govern ASS expression. Although these 4 melanoma cell lines do not express ASS protein or mRNA as detected by both immunoblot and northernblot analysis, ASS protein can be induced after these cells are grown in the presence of ADI-PEG20, but again repressed after replenishing arginine in the media. The levels of induction are different and one cell line could not be induced. Interestingly, a melanoma cell line with the highest level of induction could also be made resistant to ADI-PEG20. This resistant line possesses high levels of ASS mRNA and protein expression which cannot be repressed with arginine. Our study indicates that ASS expression in melanoma cells is complex and governed by biochemical parameters which are different among melanoma cells.
    Drug Target Insights 01/2007; 2:119-28.
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    ABSTRACT: Cisplatin resistance is complex and involves several different mechanisms. Employing cDNA microarray analysis, we have found that cisplatin resistant cells share the common characteristic of increase in ribosomal proteins and elongation factors. We hypothesize that in order to survive cisplatin treatment, cells have to synthesize DNA repair proteins, antiapoptotic proteins and growth-stimulating proteins. Thus, by blocking the translation of these proteins, one should be able to restore cisplatin sensitivity. We have studied the role of CCI-779, an ester analog of rapamycin which is known to inhibit translation by disabling mTOR, in restoring cisplatin sensitivity in a panel of cisplatin resistant cell lines. We have also determined the role of CCI-779 in P-gp1 and MRP1 mediated resistance. Our data show that CCI-779 possess antiproliferative effects in both cisplatin sensitive and resistant cell lines, but shows no effect in P-gp1 and MRP1 overexpressing cell lines. Importantly, CCI-779 at 10 ng/ml (less that 10% of the growth inhibitory effect) can increase the growth inhibition of cisplatin by 2.5-6 fold. Moreover, CCI-779 also enhances the apoptotic effect of cisplatin in cisplatin resistant cell lines. In these resistant cells, adding CCI-779 decreases the amount of 4E-BP phosphorylation and p-70S6 kinase phosphorylation as well as lower the amount of elongation factor while cisplatin alone has no effect. However, CCI-779 can only reverse P-gp mediated drug resistance at a higher dose(1 ug/ml). We conclude that CCI-779 is able to restore cisplatin sensitivity in small cell lung cancer cell lines selected for cisplatin resistance as well as cell lines derived from patients who failed cisplatin. These findings can be further explored for future clinical use. On the other hand, CCI-779 at achievable clinical concentration, has no growth inhibitory effect in P-gp1 or MRP1 overexpressing cells. Furthermore, CCI-779 also appears to be a weak MDR1 reversal agent. Thus, it is not a candidate to use in MDR1 or MRP1 overexpressing cells.
    Molecular Cancer 02/2005; 4(1):25. · 5.13 Impact Factor
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    ABSTRACT: Collagen type I production has been shown to play a role in malignant transformation. We examined procollagen type I expression in brain tumors and with histopathological grading. Expression levels of procollagen alpha 1 type 1 were determined in 5 glioma cell lines by RT-PCR, Northern, and Western blot analysis. In addition, 41 primary brain tumors and 2 metastatic lung cancers to the brain were examined by PCR. Of the 5 glioma cell line analyzed, 3 (glioma 1, SW-1783 and U-118) expressed procollagen alpha 1 type I and were sensitive to vitamin D3 (VD3). In contrast, 2 of the cell lines (U-373 and T-98G) lacked procollagen alpha 1 type 1 expression. In patients' samples, 14 of 15 anaplastic and low grade gliomas expressed procollagen alpha 1 type I, and 12 of the 14 expressed high levels. In contrast, only 12 of 21 high grade gliomas from patients expressed procollagen alpha 1 type1 and among these, only 4 of the 12 expressed high levels. Thus, there is an inversed correlation between procollagen alpha 1 type 1 expression and histopathological grading (R2=- 0.56, p=0.0005). Our data suggest that procollagen alpha 1 type I expression occurs more commonly in intermediate and low grade gliomas and may assist in histopathological grading.
    Cancer Investigation 02/2005; 23(7):577-81. · 2.24 Impact Factor
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    ABSTRACT: Cisplatin (CDDP) resistance is one of the major impediments in cancer chemotherapy. In an attempt to define this complex mechanism(s) of resistance, we have identified 7 cDNA fragments which are overexpressed in CDDP resistant small cell lung cancer cell line (SR-2) using PCR selected cDNA subtraction. One of these fragments was identical with nucleotide 3657-4042 of MRP4. The other fragments share sequence homology with elongation factor alpha, human placenta villi cDNA, heat shock protein (Hsp70), ribosomal RNA, BNP1 brain specific Na-dependent inorganic phosphate cotransporter and telomeric catalytic subunit. Examination of other MRP members (MRP1, 2, 3, 5, 6) did not show discernable differences in their expression between the parental (SCLC1) and the CDDP-resistant variant (SR-2). Full length MRP4 cDNA was obtained from SCLC1 and SR-2. Both cell lines carry a point mutation at nucleotide 3532 while SR-2 carries two additional mutations at 3228 and 3246. Since MRP4 is known to transport azidiothymidine (AZT) and overexpression of MRP4 confers AZT resistance, we have studied growth inhibitory effects of AZT and [3H]-AZT accumulation. Interestingly, SR-2 is more sensitive to AZT while accumulating lesser amounts of [3H]-AZT. The thymidine kinase activity is similar in both cell lines. Thus, the increased sensitivity to AZT in SR-2 could not be solely due to mutation of MRP4. These findings are most likely due to the inhibitory effects of telomere catalytic subunit by AZT. Thus, certain biochemical changes induced by CDDP can be explored for future treatment to overcome this form of resistance.
    International Journal of Oncology 08/2003; 23(1):173-9. · 2.66 Impact Factor

Publication Stats

131 Citations
22.96 Total Impact Points

Institutions

  • 2012
    • South Florida Veterans Affairs Foundation for Research and Education
      Miami, Florida, United States
  • 2005–2012
    • University of Miami Miller School of Medicine
      • Sylvester Comprehensive Cancer Center
      Miami, FL, United States
  • 2003–2005
    • University of Miami
      • Sylvester Comprehensive Cancer Center
      كورال غيبلز، فلوريدا, Florida, United States