Potential Clinical Applications of Stem Cells in Regenerative Medicine.

The field of regenerative medicine is looking for a pluripotent/multipotent stem cell able to differentiate across germ layers and be safely employed in therapy. Unfortunately, with the exception of hematopoietic stem/progenitor cells (HSPCs) for hematological applications, the current clinical results with stem cells are somewhat disappointing. The potential clinical applications of the more primitive embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have so far been discouraging, as both have exhibited several problems, including genomic instability, a risk of teratoma formation, and the possibility of rejection. Therefore, the only safe stem cells that have so far been employed in regenerative medicine are monopotent stem cells, such as the abovementioned HSPCs or mesenchymal stem cells (MSCs) isolated from postnatal tissues. However, their monopotency, and therefore limited differentiation potential, is a barrier to their broader application in the clinic. Interestingly, results have accumulated indicating that adult tissues contain rare, early-development stem cells known as very small embryonic-like stem cells (VSELs), which can differentiate into cells from more than one germ layer. This chapter addresses different sources of stem cells for potential clinical application and their advantages and problems to be solved.

Micro-RNA-186-5p inhibition attenuates proliferation, anchorage independent growth and invasion in metastatic prostate cancer cells.

BACKGROUND: Dysregulation of microRNA (miRNA) expression is associated with hallmarks of aggressive tumor phenotypes, e.g., enhanced cell growth, proliferation, invasion, and anchorage independent growth in prostate cancer (PCa). METHODS: Serum-based miRNA profiling involved 15 men diagnosed with non-metastatic (stage I, III) and metastatic (stage IV) PCa and five age-matched disease-free men using miRNA arrays with select targets confirmed by quantitative real-time PCR (qRT-PCR). The effect of miR-186-5p inhibition or ectopic expression on cellular behavior of PCa cells (i.e., PC-3, MDA-PCa-2b, and LNCaP) involved the use bromodeoxyuridine (BrdU) incorporation, invasion, and colony formation assays. Assessment of the impact of miR-186-5p inhibition or overexpression on selected targets entailed microarray analysis, qRT-PCR, and/or western blots. Statistical evaluation used the modified t-test and ANOVA analysis. RESULTS: MiR-186-5p was upregulated in serum from PCa patients and metastatic PCa cell lines (i.e., PC-3, MDA-PCa-2b, LNCaP) compared to serum from disease-free individuals or a normal prostate epithelial cell line (RWPE1), respectively. Inhibition of miR-186-5p reduced cell proliferation, invasion, and anchorage-independent growth of PC-3 and/or MDA-PCa-2b PCa cells. AKAP12, a tumor suppressor target of miR-186-5p, was upregulated in PC-3 and MDA-PCa-2b cells transfected with a miR-186-5p inhibitor. Conversely, ectopic miR-186-5p expression in HEK 293 T cells decreased AKAP12 expression by 30%. Both pAKT and ß-catenin levels were down-regulated in miR-186-5p inhibited PCa cells. CONCLUSIONS: Our findings suggest miR-186-5p plays an oncogenic role in PCa. Inhibition of miR-186-5p reduced PCa cell proliferation and invasion as well as increased AKAP12 expression. Future studies should explore whether miR-186-5p may serve as a candidate prognostic indicator and a therapeutic target for the treatment of aggressive prostate cancer.

Inhibition of autophagy prevents cadmium-induced prostate carcinogenesis.

BACKGROUND: Cadmium, an established carcinogen, is a risk factor for prostate cancer. Induction of autophagy is a prerequisite for cadmium-induced transformation and metastasis. The ability of Psoralidin (Pso), a non-toxic, orally bioavailable compound to inhibit cadmium-induced autophagy to prevent prostate cancer was investigated. METHODS: Psoralidin was studied using cadmium-transformed prostate epithelial cells (CTPE), which exhibit high proliferative, invasive and colony forming abilities. Gene and protein expression were evaluated by qPCR, western blot, immunohistochemistry and immunofluorescence. Xenograft models were used to study the chemopreventive effects in vivo. RESULTS: Cadmium-transformed prostate epithelial cells were treated with Pso resulting in growth inhibition, without causing toxicity to normal prostate epithelial cells (RWPE-1). Psoralidin-treatment of CTPE cells inhibited the expression of Placenta Specific 8, a lysosomal protein essential for autophagosome and autolysosome fusion, which resulted in growth inhibition. Additionally, Pso treatment caused decreased expression of pro-survival signalling proteins, NFκB and Bcl2, and increased expression of apoptotic genes. In vivo, Pso effectively suppressed CTPE xenografts growth, without any observable toxicity. Tumours from Pso-treated animals showed decreased autophagic morphology, mesenchymal markers expression and increased epithelial protein expression. CONCLUSIONS: These results confirm that inhibition of autophagy by Pso plays an important role in the chemoprevention of cadmium-induced prostate carcinogenesis.

Targeting aberrant expression of Notch-1 in ALDH+ cancer stem cells in breast cancer.

We have previously reported that high aldehyde dehydrogenase (ALDH) enzyme activity in breast cancer cells results in breast cancer stem cell (BCSC) properties by upregualting Notch-1 and epithelial mesenchymal markers. This results in chemoresistance in breast cancer. Here, we examined the functional and clinical significance of ALDH expression by measuring the ALDH levels in breast cancer tissues by immunohistochemistry. There was a significantly higher ALDH expression in higher grade breast cancer tumor tissues (Grade- II and III) versus normal breast tissues. Injection of BCSC (ALDH+ and CD44+ /CD22- ) cells resulted in aggressive tumor growth in athymic mice versus ALDH- cells. The ALDH+ and CD44+ /CD22- tumors grow rapidly and are larger than ALDH- tumors which were slow growing and smaller. Molecularly, ALDH+ tumors expressed higher expression of Notch-1 and EMT markers than ALDH- tumors. Oral administration of the naturally occurring Psoralidin (Pso, 25 mg/kg of body weight) significantly inhibited the growth in ALDH+ and ALDH- tumors as well. Psoralidin inhibited Notch-1 mediated EMT activation in ALDH+ and ALDH- tumors-this confirms our in vitro findings. Our results suggest that Notch-1 could be an attractive target and inhibition of Notch-1 by Psoralidin may prevent pathogenesis of breast cancer as well as metastasis. © 2016 Wiley Periodicals, Inc.

Induction of reactive oxygen species generation inhibits epithelial-mesenchymal transition and promotes growth arrest in prostate cancer cells.

Oxidative stress is one causative factor of the pathogenesis and aggressiveness of most of the cancer types, including prostate cancer (CaP). A moderate increase in reactive oxygen species (ROS) induces cell proliferation whereas excessive amounts of ROS promote apoptosis. In this study, we explored the pro-oxidant property of 3,9-dihydroxy-2-prenylcoumestan (psoralidin [pso]), a dietary agent, on CaP (PC-3 and C4-2B) cells. Pso greatly induced ROS generation (more than 20-fold) that resulted in the growth inhibition of CaP cells. Overexpression of anti-oxidant enzymes superoxide dismutase 1 (SOD1), SOD2, and catalase, or pretreatment with the pharmacological inhibitor N-acetylcysteine (NAC) significantly attenuated both pso-mediated ROS generation and pso-mediated growth inhibition in CaP cells. Furthermore, pso administration significantly inhibited the migratory and invasive property of CaP cells by decreasing the transcription of ß-catenin, and slug, which promote epithelial-mesenchymal transition (EMT), and by concurrently inducing E-cadherin expression in CaP cells. Pso-induced ROS generation in CaP cells resulted in loss of mitochondrial membrane potential, cytochrome-c release, and activation of caspase-3 and -9 and poly (ADP-ribose) polymerase (PARP), which led to apoptosis. On the other hand, overexpression of anti-oxidants rescued pso-mediated effects on CaP cells. These findings suggest that increasing the threshold of intracellular ROS could prevent or treat CaP growth and metastasis.

Activation of AKT signaling promotes epithelial-mesenchymal transition and tumor growth in colorectal cancer cells.

Activation of the serine-threonine protein kinase AKT has emerged as a central feature of epithelial-mesenchymal transition (EMT), which is the initial step for metastasis in many cancer models, including colorectal cancer. The focus of our study was to dissect the role of AKT and its molecular regulation of EMT in colorectal cancer. HCT-116 colorectal cancer cells stably overexpressing AKT (AKT/HCT-116) showed significantly higher cell proliferation compared with vector-transfected cells (pCMV/HCT-116). Elevated expression of important EMT-related transcription factors and genes such as Snail, Slug, ß-catenin, vimentin, and MMP-9 correlated with increased migration and invasion by AKT/HCT-116 cells. Further, in vivo studies confirmed that AKT/HCT-116 xenografts were highly aggressive and angiogenic in nature compared with pCMV/HCT-116 xenografts. Molecular analysis of tumor samples revealed transcriptional regulation of Snail, Slug, ß-catenin, MMP-2, and MMP-9 in AKT/HCT-116 tumors. These results were supported by immunohistochemistry analysis. Low levels of E-cadherin expression with a concomitant increase in and nuclear localization of ß-catenin were evident in AKT/HCT-116 tumors compared with control tumors. Increased microvessel formation coincident with high expression of Factor VIII and increased numbers of reticulocytes confirmed the angiogenic property of AKT/HCT-116 tumors. Our results confirm the potential role of AKT signaling in regulating EMT and angiogenesis in colorectal cancer and suggest that inhibition of AKT can serve as an important therapeutic strategy in modulating EMT in colorectal cancer growth and metastasis.

Withaferin A, a steroidal lactone from Withania somnifera, induces mitotic catastrophe and growth arrest in prostate cancer cells.

Cell cycle deregulation is strongly associated with the pathogenesis of prostate cancer. Clinical trials of cell cycle regulators that target either the G0/G1 or G2/M phase to inhibit the growth of cancers including prostate cancer are increasing. The present study focused on the cell cycle regulatory potential of the withanolide withaferin A (1) on prostate cancer cells. Compound 1 induced G2/M arrest in both prostate cancer cell lines (PC-3 and DU-145) when treated for 48 h. The G2/M arrest was accompanied by upregulation of phosphorylated Wee-1, phosphorylated histone H3, p21, and Aurora B. On the other hand, downregulation of cyclins (A2, B1, and E2) and a reduction in phosphorylated Cdc2 (Tyr15) were observed in 1-treated prostate cancer cells. In addition, decreased levels of phosphorylated Chk1 (Ser345) and Chk2 (Thr68) were evident in prostate cancer cells on treatment with 1. These results suggest that activation of Cdc2 leads to arrest in the M phase, with abnormal duplication, and initiation of mitotic catastrophe that results in cell death. In conclusion, these results show clearly the potential of 1 as a regulator of the G2/M phase of the cell cycle and as a therapeutic agent for prostate cancer.

Risk factors for SARS-CoV-2 infection among health workers in India: a case control study.

Background: COVID-19 was declared as a Public Health Emergency of International Concern on 30th January 2020. Compared to the general population, healthcare workers and their families have been identified to be at a higher risk of getting infected with COVID-19. Therefore, it is crucial to understand the risk factors responsible for the transmission of SARS-CoV-2 infection among health workers in different hospital settings and to describe the range of clinical presentations of SARS-CoV-2 infection among them. Methodology: A nested case-control study was conducted among healthcare workers who were involved in the care of COVID-19 cases for assessing the risk factors associated with it. To get a holistic perspective, the study was conducted in 19 different hospitals from across 7 states (Kerala, Tamil Nadu, Andhra Pradesh, Karnataka, Maharashtra, Gujarat, and Rajasthan) of India covering the major government and private hospitals that were actively involved in COVID-19 patient care. The study participants who were not vaccinated were enrolled using the incidence density sampling technique from December 2020 to December 2021. Results: A total of 973 health workers consisting of 345 cases and 628 controls were recruited for the study. The mean age of the participants was observed to be 31.17 ± 8.5 years, with 56.3% of them being females. On multivariate analysis, the factors that were found to be significantly associated with SARS-CoV-2 were age of more than 31 years (adjusted odds ratio [aOR] 1.407 [95% CI 1.53-1.880]; p = 0.021), male gender (aOR 1.342 [95% CI 1.019-1.768]; p = 0.036), practical mode of IPC training on personal protective equipment (aOR 1. 1.935 [95% CI 1.148-3.260]; p = 0.013), direct exposure to COVID-19 patient (aOR 1.413 [95% CI 1.006-1.985]; p = 0.046), presence of diabetes mellitus (aOR 2.895 [95% CI 1.079-7.770]; p = 0.035) and those received prophylactic treatment for COVID-19 in the last 14 days (aOR 1.866 [95% CI 0.201-2.901]; p = 0.006). Conclusion: The study was able to highlight the need for having a separate hospital infection control department that implements IPC programs regularly. The study also emphasizes the need for developing policies that address the occupational hazards faced by health workers.

Antibacterial, antioxidant, and haemolytic potential of silver nanoparticles biosynthesized using roots extract of Cannabis sativa plant.

In this study, Cannabis sativa roots extract has been employed for the biosynthesis of silver nanoparticles (AgNPs). The appearance of reddish-brown colour followed by absorption peak of AgNPs at 408 nm through UV-vis spectrophotometry suggested biosynthesis of AgNPs. The size of the particles ranged from 90-113 nm, confirmed using DLS and TEM along with zeta potential of -25.3 mV. The FTIR provided information regarding the phytochemical capping. The study was further elaborated for determining AgNPs antibacterial, antioxidant, and cellular toxicity using MIC, DPPH, MTT, and haemolytic assays, respectively. The AgNPs were significantly effective against Staphylococcus aureus (Gram-positive), as compared to that of Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli (Gram-negative). AgNPs also exhibited remarkable antioxidant potential wherein 58.01 ± 0.09% free radical scavenging was observed at a concentration of 100 µg/ml. AgNPs revealed lower cytotoxicity where cell viability was observed to be 52.38 ± 0.6% at a very high concentration of 500 µg/ml in HEK 293 cells. Further, very low toxicity was seen in RBCs i.e. 6.47 ± 0.04% at a high concentration of 200 µg/ml. Thus, the current study beholds anticipation that Cannabis sativa ethanolic root extract-mediated AgNPs may play a vital role in therapeutic.

Novel view of the adult stem cell compartment - a developmental story of germline and parental imprinting.

Evidence has accumulated that postnatal tissues contain developmentally early stem cells that remain in a dormant state as well as stem cells that are more proliferative, supplying tissue-specific progenitor cells and thus playing a more active role in the turnover of adult tissues. The most primitive, dormant, postnatal tissue-derived stem cells, called very small embryonic like stem cells (VSELs), are regulated by epigenetic changes in the expression of certain parentally imprinted genes, a molecular phenomenon previously described for maintaining primordial germ cells (PGCs) in a quiescent state. Specifically, they show erasure of parental imprinting at the Igf2-H19 locus, which keeps them in a quiescent state in a similar manner as migrating PGCs. To date, the presence of these cells in adult postnatal tissues have been demonstrated by at least 25 independent laboratories. We envision that similar changes in expression of parentally imprinted genes may also play a role in the quiescence of dormant VSELs present in other non-hematopoietic tissues. Recent data indicate that VSELs expand in vivo and in vitro after reestablishment of somatic imprinting at the Igf2-H19 locus by nicotinamide treatment in response to stimulation by pituitary gonadotrophins (follicle stimulating factor, luteinizing hormone and prolactin) and gonadal androgens and estrogens. These cells could be also successfully expanded ex vivo in the presence of the small molecule UM177.

Withaferin A Inhibits Prostate Carcinogenesis in a PTEN-deficient Mouse Model of Prostate Cancer.

We recently demonstrated that AKT activation plays a role in prostate cancer progression and inhibits the pro-apoptotic function of FOXO3a and Par-4. AKT inhibition and Par-4 induction suppressed prostate cancer progression in preclinical models. Here, we investigate the chemopreventive effect of the phytonutrient Withaferin A (WA) on AKT-driven prostate tumorigenesis in a Pten conditional knockout (Pten-KO) mouse model of prostate cancer. Oral WA treatment was carried out at two different doses (3 and 5 mg/kg) and compared to vehicle over 45 weeks. Oral administration of WA for 45 weeks effectively inhibited primary tumor growth in comparison to vehicle controls. Pathological analysis showed the complete absence of metastatic lesions in organs from WA-treated mice, whereas discrete metastasis to the lungs was observed in control tumors. Immunohistochemical analysis revealed the down-regulation of pAKT expression and epithelial-to-mesenchymal transition markers, such as ß-catenin and N-cadherin, in WA-treated tumors in comparison to controls. This result corroborates our previous findings from both cell culture and xenograft models of prostate cancer. Our findings demonstrate that the daily administration of a phytonutrient that targets AKT activation provides a safe and effective treatment for prostate cancer in a mouse model with strong potential for translation to human disease.

Withaferin-A suppress AKT induced tumor growth in colorectal cancer cells.

The oncogenic activation of AKT gene has emerged as a key determinant of the aggressiveness of colorectal cancer (CRC); hence, research has focused on targeting AKT signaling for the treatment of advanced stages of CRC. In this study, we explored the anti-tumorigenic effects of withaferin A (WA) on CRC cells overexpressing AKT in preclinical (in vitro and in vivo) models. Our results indicated that WA, a natural compound, resulted in significant inhibition of AKT activity and led to the inhibition of cell proliferation, migration and invasion by downregulating the epithelial to mesenchymal transition (EMT) markers in CRC cells overexpressing AKT. The oral administration of WA significantly suppressed AKT-induced aggressive tumor growth in a xenograft model. Molecular analysis revealed that the decreased expression of AKT and its downstream pro-survival signaling molecules may be responsible for tumor inhibition. Further, significant inhibition of some important EMT markers, i.e., Snail, Slug, ß-catenin and vimentin, was observed in WA-treated human CRC cells overexpressing AKT. Significant inhibition of micro-vessel formation and the length of vessels were evident in WA-treated tumors, which correlated with a low expression of the angiogenic marker RETIC. In conclusion, the present study emphasizes the crucial role of AKT activation in inducing cell proliferation, angiogenesis and EMT in CRC cells and suggests that WA may overcome AKT-induced cell proliferation and tumor growth in CRC.

Oral administration of withaferin A inhibits carcinogenesis of prostate in TRAMP model.

We previously reported that withaferin A (WA), a natural compound, deters prostate cancer by inhibiting AKT while inducing apoptosis. In the current study, we examined its chemopreventive efficacy against carcinogenesis in the prostate using the transgenic adenocarcinoma of mouse prostate (TRAMP) model. Two distinct sets of experiments were conducted. To determine whether WA delays tumor progression, it was given before cancer onset, at week 6, and until week 44. To determine its effect after the onset of prostate cancer, it was given from weeks 12 to 35. In both strategies, oral administration of WA effectively suppressed tumor burden when compared to vehicle-treated animals. No toxicity was seen in treated animals at gross pathological examination. Western blot analysis and immunohistochemistry of tumor sections revealed that in TRAMP controls, AKT and pAKT were highly expressed while nuclear FOXO3a and Par-4 were downregulated. On the contrary, treated mice showed inhibition of AKT signaling and activation of FOX03a-Par-4-induced cell death. They also displayed inhibition of mesenchymal markers such as ß-catenin, vimentin, and snail as well as upregulation of E-cadherin. Because expressions of the angiogenic markers factor VIII and retic were downregulated, an anti-angiogenic role of WA is suggested. Overall, our results suggest that WA could be a promising anti-cancer agent that effectively inhibits carcinogenesis of the prostate.

Activation of AKT negatively regulates the pro-apoptotic function of death-associated protein kinase 3 (DAPK3) in prostate cancer.

The activation of AKT governs many signaling pathways and promotes cell growth and inhibits apoptosis in human malignancies including prostate cancer (CaP). Here, we investigated the molecular association between AKT activation and the function of death-associated protein kinase 3 (DAPK3) in CaP. An inverse correlation of pAKT and DAPK3 expression was seen in a panel of CaP cell lines. Inhibition of AKT by wortmannin/LY294002 or overexpression of DAPK3 reverts the proliferative function of AKT in CaP cells. On the other hand, ectopic expression of AKT inhibited DAPK3 function and induced proliferation of CaP cells. In addition, AKT over-expressed tumors exhibit aggressive growth when compared to control vector in xenograft models. The immunohistochemistry results revealed a down-regulation of DAPK3 expression in AKT over-expressed tumors as compared to control tumors. Finally, we examined the expression pattern of AKT and DAPK3 in human CaP specimens - the expected gradual increase and nuclear localization of pAKT was seen in higher Gleason score samples versus benign hyperplasia (BPH). On the contrary, reduced expression of DAPK3 was seen in higher Gleason stages versus BPH. This suggests that inhibition of DAPK3 may be a contributing factor to the carcinogenesis of the prostate. Understanding the mechanism by which AKT negatively regulates DAPK3 function may suggest whether DAPK3 can be a therapeutic target for CaP.

miR-301a expression: A prognostic marker for prostate cancer.

PURPOSE: The diagnosis and treatment of prostate cancer (CaP) continues to be challenging, as prostate-specific antigen (PSA) appears to be overly sensitive and biopsy is the only reliable method for confirmation. Hence, the goal of the study is to identify a biomarker that could distinguish malignant cancer from benign prostatic hyperplasia (BPH) during the early diagnosis of the disease. MATERIALS AND METHODS: A total of 75 formalin fixed paraffin embedded (FFPE) with matching controls, 4 paired metastatic tumors, 6 fresh tumor tissues and BPH (13 cases) with their clinical diagnosis were selected for this study. Prostate cancer cell lines and normal prostate epithelial cell lines were obtained from ATCC and subjected to phenotypic analysis. RESULTS: We observed significant differential expression of miR-301a in CaP samples in comparison to BPH and adjacent benign samples. The overexpression of miR-301a activates the invasion/migration of CaP cells. In contrast, silencing miR-301a expression inhibited the colony-forming ability, adhesion, invasion and migration of CaP cells. Similarly, the overexpression of miR-301a increased cell motility in normal RWPE-1 prostate epithelial cells. Our results suggest that miR-301a is differentially expressed between BPH and CaP specimens and that the expression of miR-301a correlates with biochemical recurrence and/or metastasis in CaP patients. CONCLUSIONS: The expression of miR-301a could be a potential marker for metastasis in CaP patients. Detecting miR-301a expression during diagnosis will avoid wait and watch timelines, thus preventing morbidity.

Targeting Notch Signaling in Colorectal Cancer.

The activation of Notch signaling is implicated in tumorigenesis in the colon due to the induction of pro-survival signaling in colonic epithelial cells. Chemoresistance is a major obstacle for treatment and for the complete eradication of colorectal cancer (CRC), hence, the inhibition of Notch is an attractive target for CRC and several groups are working to identify small molecules or monoclonal antibodies that inhibit Notch or its downstream events; however, toxicity profiles in normal cells and organs often impede the clinical translation of these molecules. Dietary agents have gained momentum for targeting several pro-survival signaling cascades, and recent studies demonstrated that agents that inhibit Notch signaling result in growth inhibition in preclinical models of CRC. In this review, we focus on the importance of Notch as a preventive and therapeutic target for colon cancer and on the effect of WA on this signaling pathway in the context of colon cancer.

Molecular interplay between cdk4 and p21 dictates G0/G1 cell cycle arrest in prostate cancer cells.

This study examined the effect of 3, 9-dihydroxy-2-prenylcoumestan (pso), a furanocoumarin, on PC-3 and C4-2B castration-resistant prostate cancer (CRPC) cell lines. Pso caused significant G0/G1 cell cycle arrest and inhibition of cell growth. Molecular analysis of cyclin (D1, D2, D3, and E), cyclin-dependent kinase (cdk) (cdks 2, 4, and 6), and cdk inhibitor (p21 and p27) expression suggested transcriptional regulation of the cdk inhibitors and more significant downregulation of cdk4 than of cyclins or other cdks. Overexpression of cdk4, or silencing of p21 or p27, overcame pso-induced G0/G1 arrest, suggesting that G0/G1 cell cycle arrest is a potential mechanism of growth inhibition in CRPC cells.

Chemoprevention of breast cancer by dietary compounds.

Breast cancer is the leading cause of cancer-related deaths in women in the United States and many other countries. There is an immediate need for more effective and less toxic therapeutic and preventive strategies for many cancers, especially for breast cancer. Natural products are being tested with a hope of identifying novel potent molecules as anticancer agents. Phytochemicals and dietary compounds have been used for the treatment of various illnesses throughout history due to their safety, low toxicity, and general availability. Currently, many active phytochemicals are in clinical trials. Preclinical and clinical studies have indicated that daily consumption of dietary phytochemicals reduces the risk of several cancers. Phytochemicals can inhibit, delay, or reverse carcinogenesis by inducing detoxifying and antioxidant enzymes, by regulating inflammatory/proliferative signaling pathways, and by inducing apoptosis. This review article describes some of the potential natural cancer preventive compounds, along with a mechanistic discussion of their interactions with key cellular signal transduction pathways as well as their contribution to the suppression of breast cancer cell growth.