Anti-tumoral Effects And Mechanism Of Combination Of Curcumin And Oxaliplatin On Human Colon Cancer Cells

Colon cancer is a serious threat to human life and health of malignant tumors, and itsincidence is ranked the second malignant tumors in western developed countries. With thepeople’s living habits and diet changes, the incidence of colon cancer in China showed anincreasing trend, the incidence rate of increase is twice the world average, is ranked the fourthin the incidence of malignant diseases. How effective prevention and treatment of coloncancer has become one of the focus of attention of the medical profession. In addition to thetraditional surgery, radiotherapy and chemotherapy, to find efficient, low toxicity drugs andstudy combining traditional Chinese medicine and western medicine treatment is still to beresolved in the colon cancer treatment. Natural medicine because of its multi-target,multi-link and multi-channel anti-tumor effect, becoming a hot spot of the clinical anticancerdrug research.Curcumin (diferuloylmethane) is a natural polyphenol extracted from the rhizomes of theplant Curcuma longa Linn. It has wide range of pharmacological effects, anti-cancer is one ofthe main function. Oxaliplatin is a third generation platinum anti-cancer drugs after cisplatinand carboplatin. It has a wide range of anti-tumor spectrum, and is commonly used drugs inthe clinical treatment of colon cancer. Therefore, in-depth study of the anti-cancer activity ofcurcumin and its mechanism, and further studying anti-colon cancer effect of combination ofcurcumin and oxaliplatin could establish some foundation for colon cancer treatment inclinical application. In this research, anti-tumoral effects and mechanism of combination ofcurcumin and oxaliplatin on human colon cancer cells in vitro and in vivo were investigatedwith colon cancer cells LoVo and colon cancer-bearing nude mice models through flowcytometry, transmission electron microscopy (TEM), reverse transcription-polymerase chainreaction (RT-PCR), western blotting, immunohistochemistry and immunofluorescencemethods. The main results as follow:1. Curcumin could inhibit the growth of the tumor cells of different tissue origin (LoVo,SW480, MCF-7, BGC-823and SMMC-7721), has a dose-and time-dependent relationship;the growth of inhibition is more obvious in LoVo and MCF-7cells, while in normal cellsHK-2more than48h, when doses of more than20μg/mL, its growth has a certain inhibition.Suggesting that curcumin inhibition of cell growth may have tissue-specific, may not have asignificant tumor cell-specific.2. Curcumin could significantly inhibit the growth and proliferation in LoVo cells, has abetter concentration-and time-dependent relationship; The inhibitory concentration50% (IC50) of curcumin were12.70±0.06,8.80±0.50and4.97±0.71μg/mL in LoVo cells at24,48and72h. Curcumin could make LoVo cell morphological changes, showing the typicalcharacteristics of apoptotic cells; arrest cell cycle at S phase, and induce apoptosis of LoVocells.3. Curcumin can significantly reduce mitochondrial membrane potential, prompting therelease of cytochrome c, inhibition the expression of Bcl-2, Bcl-xL, c-myc and survivinprotein, up-regulation the expression of Bax, caspase-3and p53protein, increase the activityof caspase-9in LoVo cells, and induced apoptosis of LoVo cells through the mitochondrialpathway.4. Combination of curcumin and oxaliplatin could synergistically inhibit proliferation ofLoVo cells, make the LoVo cells obvious morphological changes, arrest cell cycle at S phase,induce a large number of tumor cells death.5. Combination of curcumin and oxaliplatin could synergistically reduce significantlymitochondrial membrane potential, activate the expression of caspase-3and caspase-9, inhibitthe expression of Bcl-2and Bcl-xL and promote the expression of Bax at the mRNA level,down-regulation the expression of Bcl-2, c-myc, and survivin protein, and promote theexpression of Bax and caspase-3at the protein level.6.50mg/kg dose of curcumin can inhibit the growth of LoVo colonic xenografts in nudemice, and combination of curcumin and oxaliplatin group treatment could emerge additiveeffect on the inhibition of tumor growth, tumor inhibition rates were59.47%and70.56%,respectively. Curcumin group and combination of curcumin and oxaliplatin group treatmentdid not influence nude mice blood system, liver and kidney organs. Combination of curcuminand oxaliplatin group treatment could interfere with cell cycle arrest at S phase, inducingtumor cells apoptosis and necrosis. Using RT-PCR, western blotting andimmunohistochemistry to clarify the combination of curcumin and oxaliplatin treatment cansignificantly inhibit the Bcl-xL, Bcl-2, c-myc and survivin expression, promote the expressionof Bax, down-regulation the expression of HSP70protein, and activated caspase-3and PARPexpression in tumor tissue of tumor-bearing nude mice.7. Curcumin could regulate the antioxidant system of colon cancer-bearing nude mice.Experiments in vivo showed that curcumin group and combination of curcumin andoxaliplatin group treatment could increase the levels of serum T-SOD and T-AOC, butdecrease the MDA level in tumor-bearing nude mice. They also improved the T-SOD, T-AOCand GR levels in liver and kidney of tumor-bearing nude mice, Furthermore, curcumin groupand combination of curcumin and oxaliplatin group treatment could increase the T-AOC level in spleen tissues, but not influence the T-SOD level in spleen, the GR level of spleen tissuewas the highest in curcumin group. To tumor tissues, curcumin group and combination ofcurcumin and oxaliplatin group treatment decreased T-AOC, T-SOD and GR levels. Besidesthat, the serum LDH level of tumor-bearing nude mice was suppressed by the treatment ofcurcumin group and combination of curcumin and oxaliplatin group. Curcumin grouptreatment could not influence the level of serum AKP, but combination of curcumin andoxaliplatin group treatment could increase the level of serum AKP significantly. Experimentsin vitro further showed that curcumin had strong effects on scavenging·OH radical, O2·-radical and DPPH radical.In summary, curcumin could inhibit LoVo cells growth, induce LoVo cells arrest andapoptosis, Curcumin combination with oxaliplatin had a synergistic inhibitory effect on thegrowth of LoVo cells. Combination of curcumin and oxaliplatin used in the treatment of coloncancer, not only mitigated the toxicity of oxaliplatin, but also increased of anti-cancer effects,and did not find toxicity overlap of the two drugs. This suggested that the combination ofcurcumin and oxaliplatin treatment for colon cancer is feasible and worth of clinicalapplication.