Herbal medicines have become principal and complementary anti-neoplastic agents for its special pharmacologic actions, slight toxicity and reduced side effects. Three important anti-neoplastic mechanisms are reversing the multidrug resistance of tumor cells, inhibiting tumor angiogenesis, suppressing tumor angiogenesis, and enhancing body immunity. Herbal medicines are hopefully becoming more specific to their targets.
The comprehensive therapies against neoplasm, one of the fatal diseases, mainly include surgery, chemotherapy, radiotherapy, biotherapy, etc. However, the curative effects are not satisfactory. In current anti-neoplasm medicines, herbal medicines play an important role because of its holistic treatments and mixed functions of tonification and purgation. It is characterized by low side-effect, alleviation for suffering, increase of life quality and sustainable efficacy. Three important anti-neoplastic mechanisms of herbal extracts and their promising future are discussed hereinafter.
1. The reversal of tumor cells
Multi-drug resistance (MDR) is the primary reason for the failure of chemotherapy, referring to the fact when tumor cells shows resistance to one anti- neoplastic drug, they also cross resist to other drugs with different structures or mechanisms. The mechanism of MDR is associated with MDR-related proteins (MRP), lung resistance-related protein (LRP), P-glycoprotein (P-gp), glutathione (GSH), glutathione 2S transferase. Liu et al. found the injection of Panax Notoginseng Saponins (PNS) can inhibit the drug-pumping of tumor cells to partly achieve reversal of MDR of drug-resistant breast cancer cell by suppressing MDR genes and its P-gP glycoprotein product. Therefore, searching for MDR reversal agents and recovering the sensitivity of MDR cells to anti-neoplastic medicines provide a main therapy for neoplasm.
2. Inhibitiontumor angiogenesis
It is required to stimulate angiogenesis when tumor growth to >2 mm. Tumor vessel is new immature vessel with disorder branches, incomplete basilar membrane and high permeability, which has higher possibility to be penetrated by tumor cells for metastasis than mature vessel. Therefore, it is effective to correct branch of tumor blood vessels and suppress tumor angiogenesis for inhibiting neoplasm and its metastasis. Study results show that lots of herbal medicines and extracts can suppress tumor angiogenesis. Chen et al. studied the tumor growth inhibition of ginsenoside RS3 by analyzing the expression of several vasostimulating factors including VEGF, Fit and MMP-2 and results indicate that RS3 effect on tumor angiogenesis through different target spots. It is suggested that Tripterygium wilfordii can reduce VEGF mRNA and protein expression of Raji cells, and assumed that the inhibition effect of Tripterygium wilfordii on tumor cells growth, proliferation and metastasis is associated with suppressing tumor angiogenesis.
3. Enhancement of immunity
The immunity system is responsible for monitoring abnormal cells and malignant cells in early phase, and removing them in time. However, tumor cells can escape or inhibit immunity function. As a result, improving immunity is an effective method towards anti-neoplasm development and progression. Traditional Chinese medicine theory indicates that herbal medicine can enhance immunity by supporting body to resist diseases, activating blood and dissolving stasis, and invigorating Qi (a traditional term of Chinese medicine, similar to energy) and strengthening spleen and so on, which are important mechanisms for herbal medicine to suppress neoplasm. The research by Li et al. found that Linglong liquidum extractum (LLE) effectively suppresses the tumor growth in tumor bearing mice through the improved immunity reaction which antagonize the inhibition of immunity function. Researches in recently years show that deer horn polysaccharides, radix codonopsis, Panax ginseng, atractylodes can increase T cell ratio and enhance phagocyte function and other related effects.
4. Prospect
Nowadays, herbal extracts and medicines are more and more important for anti-neoplastic therapy researches. With the further research of neoplastic pathogenesis and the development of isolation and purifying techniques, it is believed that new single-ingredient anti-neoplastic agents with higher purity and more specific target can be developed from herbal medicines.
