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Cancer is a group of more than 100 different diseases, characterized by uncontrolled cellular growth, local tissue invasion, and distant metastases. The four most common cancers are prostate, breast, lung, and colorectal cancer (Balmer et al., 2005). Every year there are approximately 2, 20,000 new cases of cancer. Almost one-third of the population will develop cancer during their lifetime, and of these 70% will die of the disease, 1, 50,000 deaths a year. In recent years, the approach has been changing rapidly as a consequence of fundamental advances in cancer biology, the isolation of genes responsible for hereditary disposition to cancer, increasing accuracy in diagnosis and staging, and major developments in the use of radiotherapy and chemotherapy (Sohami, 2002).
Most cancer treatments are accompanied by a degree of herbal supplements. There are beneficial effects of medicinal plants on cancer. It does not need to be all chemicals and radiation. Several therapies include herbal remedies to improve the quality of life for the sufferer as well and aid the potent medicine to do its job of ridding the body of this fatal disease. Around the world there are countless herbs, trees and fruits that possess anti-cancer properties. Cancer patients becoming are more educated about this topic by learning about the positive effects of medicinal plants on cancer and finding their own success by taking high quality supplements to beat the disease (Spring, 2010).
Plant derived natural products such as flavonoids, terpenes, alkaloids etc have received considerable attention in recent years due to their diverse pharmacological properties including cytotoxic and cancer chemopreventive effects (Babu et al., 2002). The search for anti-cancer agents from plant sources started in the 1950s with the discovery and development of the vinca alkaloids, vincristine and vinblastine, and the isolation of the cytotoxic podophyllotoxines. These discoveries prompted the United States National Cancer Institute (NCI) to initiate an extensive plant collection program in 1960, focused mainly in temperature regions. This led to the discovery of many novel chemotypes showing a range of cytotoxic activities, including the taxanes and campothecins (Cragg and Newman, 2005).
Natural products discovered from medicinal plants have played an important role in the treatment of cancer. Natural products or natural product derivatives comprised 14 of top 35 drugs in 2000 based on worldwide sales (Butlet, 2004). Plant based medicine has definitely found a role in cancer treatment (chemotherapy), and the mechanism of interaction between many phytochemicals and cancer cells has been studied extensively. In particular, there is growing interest in the pharmacological evaluation of various plants used in, Indian tradition system of medicine. There are more than 270,000 higher plants existing on this planet. But only a small portion has been explored phytochemically. So, it is anticipated that plants can provide potential bioactive compounds for the development of new 'leads' to combat cancer diseases (Shoeb, 2006).
The phytochemical screening of HEBE and AGSE showed presence of useful chemical compounds such as alkaloids, flavonoids, glycosides, phenolics, steroids, tannins and terpenoids, whereas saponin is absent in HEBE and it was found present in AGSE. Medicinal plants may contain many kinds of chemical components and that their biological activities are not usually attributable to a single moiety (Cho et al., 2003).
The present study was undertaken to evaluate the cytotoxic activity of HEBE and AGSE. The cytotoxic result obtained in the present study demonstrates for the first time, to the best of our knowledge, that HEBE and AGSE caused a dose-dependent growth inhibitory effect.
Chemoprevention, which includes the use of synthetic or natural agents (alone or in combination) to block the development of cancer in human beings, is an extremely promising strategy for cancer prevention (Koppikar et al., 2010). The control of cell proliferation is crucial in maintaining cellular homeostasis and loss of this mechanism is a principle hallmark of cancer cells. Thus the inhibition of tumor cell growth without side effects is recognized as an important target for cancer therapy (Kametani et al., 2007).
In this study, methanolic extracts were used. Since it is known that different cell lines might exhibit different sensitivities towards a cytotoxic compound, the use of more than one cell line is therefore considered necessary in the detection of cytotoxic compounds (Kamuhabwa et al., 2000). Bearing this in mind, two cell lines of different histological origin were used in the present study. Cytotoxic specificity of plant extracts is likely to be due to the presence of different classes of compounds in the extract, as it has been documented in the case of known classes of compounds (Cragg et al., 1994).
In vitro confirmation of the extract's toxicity was done on DLA cell lines. Percentage of viable cell can be obtained by performing trypan blue dye exclusion technique. Trypan blue is a blue acid dye that has two azo chromophores group. Trypan blue will not enter into the cell wall of plant cells grown in culture. Trypan blue is an essential dye, use in estimating the number of viable cells present in a population (Patel et al., 2009). In this study HEBE and AGSE inhibits growth in DLA in a dose dependent manner. The results of the trypan blue dye exclusion assay indicated that HEBE and AGSE extracts could inhibit the growth of DLA cells significantly (P> 0.01) in culture (Shrivastava and Ganesh, 2010).
The cytotoxicity activity was carried out by using standard MTT assay. This Colorimetric assay is based on the capacity of mitochondria succinate dehydrogenase enzymes in living cells to reduce the yellow water soluble substrate 3- (4, 5-dimethyl thiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) into an insoluble, colored formazan product which is measured spectrophotometrically. Since reduction of MTT can only occur in metabolically active cells, the level of activity is a measure of the viability of the cells (Wilson, 2000). MTT reduction as a cell viability measurement is now widely chosen as the most advantageous end point (Wahab et al., 2009). The results of MTT assay indicated that HEBE and AGSE significantly (P>0.01) inhibited the proliferation of L929 cells in a dose dependent manner.
These cancer effects were further studied using morphological assessment of cancer cells using agarose gel electrophoresis (Cruchten and Broeck, 2002).
Anti-tumor agents can modulate apoptosis, may be able to affect the steady state of cell populations that are helpful in the management and therapy of cancer (Ramnath et al., 2009). There are two ways for cells to die: death by injury and death by suicide. The pattern of events in death by suicide is called apoptosis (Adams, 2003). Programmed cell death is needed whenever tissue modelling is required, during embryogenesis, for the removal of old cells and to prevent overgrowth after repair of cell loss by injury (Kerr et al., 1972). Programmed cell death is also needed to destroy cells that represent a threat to the integrity of the organism, such as virus-infected cells, effectors cells of the immune system that are no longer necessary and cells with DNA damage that can become cancerous. The mechanism of apoptosis is switched on by the imbalance between proapoptotic (death signals) and antiapoptotic (survival signals) factors. This happens in both normal and cancer cells. Dysregulation of apoptosis occurs in cancer cells (Marsoni and Damia, 2004).
In our study, HEBE and AGSE cause cell growth inhibition and induce apoptosis differentially in cancer cells. Apoptosis is a well identified biological response exhibited by cells after suffering DNA damage and is a useful marker for screening compounds for subsequent development as possible anticancer agent (Arulvasu et al, 2010). Most of the cytotoxic anticancer drugs in current use have been shown to induce apoptosis in susceptible cells. It has been established that apoptotic cells display DNA fragmentation at internucleosomal sites followed by morphological changes and loss of membrane integrity (Fan et al., 2005).
Further studies confirmed that, the cytotoxicity potential of HEBE and AGSE are closely associated with chromatin condensation, one of the well markers for apoptosis. The loss of chromatin integrity is often induced by activated caspases. It could be established that nuclear changes as a part of the apoptosis are followed by the loss of membrane integrity there by making trypan blue permeable. This study revealed that the potency of HEBE and AGSE to bring about the morphological changes like cell shrinkage, compaction and segregation of the nuclear chromatin, with the result of chromatin margination and condensation of the cytoplasm (Kerr et al., 1972). Progression of the condensation is accompanied by convolution of the nuclear and cell outlines followed by breaking up of the nucleus into discrete fragments and by budding of the cell as a whole to produce membrane-bounded apoptotic bodies (Merlin, 2010). In addition, apoptotic typical DNA strand-breaks were observed by means of gel electrophoresis (Sharma et al., 2007). This induction of apoptosis in tumor cells that make them more render for host phagocytic clearance without initiating inflammation, could be attributed for the extracts tumoricidal activity.
The burden of venous thromboembolism (VTE) is a challenging problem in the medical management of cancer patients. The well-known association between cancer and VTE can now be rigorously studied with modern molecular techniques (Buller et al., 2007). The association between cancer and venous thrombosis was first recognized more than 100 years ago by Trousseau. Large population-based epidemiologic studies have shed light on the relative frequency of VTE and cancer types, and clinical trials of cancer therapy have defined additional risk factors that compound the thrombotic risk (Solymoss, 2008).
Cancer-associated venousthromboembolism (VTE) has significant clinical consequences for patients. Thromboembolism is a leading cause of death in cancer patients and cancer patients who develop VTE have a significantly worse survival. Cancer patients with VTE also suffer a higher rate of both bleeding complications and recurrent VTE (Khorana et al., 2007). In cancer patients VTE complications are common and the second leading cause of death. Of every seven patients with cancer who die in hospital, one dies of pulmonary embolism. Compared with non-cancer patients the risk of developing symptomatic VTE is six to seven times higher in cancer patients, with similar risks for the components of VTE (Buller et al., 2007).
The treatment of cancer patients for VTE has been associated with a high risk of recurrent thrombosis and of bleeding complications. However, recent data point to improved patient outcome with the use of long-term low molecular weight heparin therapy. Cancer patients who also have VTE are at increased risk of mortality (Sørensen et al., 2000), but there are intriguing suggestions concerning the benefit of low molecular weight heparin for improved cancer survival. A recently published guideline facilitates the practice of evidence-based VTE prevention and treatment in cancer patients, and sets the stage for future directions in this important domain (Lyman et al., 2007).
Plants have been used as a major medicinal source, with interest in herbal formulations increasing globally over the past decade. In addition, extracts of natural products provide a useful source of bioactive compounds which can be developed as drugs directly or provide novel structural templates (Rahman et al., 2001). A selection of plants, most of which are known to have an anticancer activity, available in the Eastern Cape Province of South Africa was chosen to test for possible antithrombotic and anticoagulant activities. This could identify plants traditionally used in the treatment of cancer that have the additional benefit of an anticoagulant activity (Vanwyk et al., 1997).
In vitro anticoagulation study revealed that HEBE and AGSE display anticoagulant activity. Plasma obtained from human blood had a prolonged clotting time relative to the control groups. Blood clotting process is very complex, involving many factors found in the plasma and tissues. It involves both the intrinsic and extrinsic pathways (Brown, 1988; Jandl, 1996). Inhibitors (anticoagulants) and activators (procoagulant) of blood coagulation may affect any of the factors. The anticoagulant activities of compounds were measured by PT and APTT, and then compared with those of heparin. PT is used to characterize the extrinsic coagulation factors: factors V, VII, X, prothrombin and fibrinogen while APTT is used for the evaluation of coagulation factors such a VIII, IX, XI, XII and prekallikerin in the intrinsic blood coagulation pathway.
In this study both HEBE and AGSE showed significant increase in PT at all doses (100-800µg/ml). In Prothrombin time assay tissue thromboplastin, in the presence of calcium ions, is an activator which initiates the extrinsic pathway of coagulation. When a mixture of tissue thromboplastin and calcium ions is added to normal anticoagulated plasma, the clotting mechanism is initiated leading to formation of a fibrin clot. If a deficiency exists within the extrinsic pathway, the time required for clot formation will be prolonged depending on the severity of the deficiency. Prolongation in PT may be due to decrease in coagulation factors like V, VII and X involved in extrinsic pathway.
Anticoagulant activity of HEBE and AGSE were also characterized by APTT. When the degree of HEBE and AGSE increased, APTT prolonged respectively. Prolongation of APTT may be due to decrease in coagulation factors such as VIII, IX , XI, XII and prekallikrein involve in intrinsic pathway (chan et al.,2007). PT and APTT are often used to assess variation in coagulation factors (Yuan et al., 2007).
Here warfarin is used as the reference standard. It stops the blood from clotting within the blood vessels. Warfarin inhibit the effective synthesis of biologically active forms of the vitamin K-dependent clotting factors II, VII, IX and X as well as the regulatory factors protein C, protein S and protein Z and causes prolongation of PT (Gage et al., 2000). Therefore it can be assumed that both HEBE and AGSE produce the effect in a way similar to warfarin.
In conclusion, there has been a growing interest in the alternative medicine and the therapeutic properties of the natural products derived from plants in the recent years. Based on the evaluation done using the various in vitro assay models it may be concluded that Hymenodictyon excelsum Roxb. and Apium graveolens Linn. possess anticancer and anticoagulant activities. Methanolic extracts of bark of Hymenodictyon excelsum Roxb. and seeds of Apium graveolens Linn. are moderately active for the treatment of cancer. Further pharmacological research using other cancer cells is necessary in order to establish whether these plants can be used as a potential source for new anticancer medicine. The finding from this study highlight that the both extracts possessed potent anticoagulant properties. This extracts affects the clotting factor(s) in the extrinsic and intrinsic pathway by markedly reducing their levels, in concert with prolonged PT and APTT. Therefore it is suggested that further work could be done on the identification and isolation of the active constituents and the exact mechanism responsible for both the activities should be explored.