Ruma Sarkar

Sulphoraphane, a naturally occurring isothiocyanate induces apoptosis in breast cancer cells by targeting heat shock proteins

Heat shock proteins (HSPs) are involved in protein folding, aggregation, transport and/or stabilization by acting as a molecular chaperone, leading to inhibition of apoptosis by both caspase dependent and/or independent pathways. HSPs are overexpressed in a wide range of human cancers and are implicated in tumor cell proliferation, differentiation, invasion and metastasis. HSPs particularly 27, 70, 90 and the transcription factor heat shock factor1 (HSF1) play key roles in the etiology of breast cancer and can be considered as potential therapeutic target. The present study was designed to investigate the role of sulphoraphane, a natural isothiocyanate on HSPs (27, 70, 90) and HSF1 in two different breast cancer cell lines MCF-7 and MDA-MB-231 cells expressing wild type and mutated p53 respectively, vis-à-vis in normal breast epithelial cell line MCF-12F. It was furthermore investigated whether modulation of HSPs and HSF1 could induce apoptosis in these cells by altering the expressions of p53, p21 and some apoptotic proteins like Bcl-2, Bax, Bid, Bad, Apaf-1 and AIF. Sulphoraphane was found to down-regulate the expressions of HSP70, 90 and HSF1, though the effect on HSP27 was not pronounced. Consequences of HSP inhibition was upregulation of p21 irrespective of p53 status. Bax, Bad, Apaf-1, AIF were upregulated followed by down-regulation of Bcl-2 and this effect was prominent in MCF-7 than in MDA-MB-231. However, very little change in the expression of Bid was observed. Alteration in Bcl-2 Bax ratio resulted in the release of cytochrome c from mitochondria and activation of caspases 3 and 9 which are in agreement with apoptotic index values. Sulphoraphane therefore can be regarded as a potent inducer of apoptosis due to HSP modulation in breast cancer cells.

Phenethyl isothiocyanate, by virtue of its antioxidant activity, inhibits invasiveness and metastatic potential of breast cancer cells: HIF-1α as a putative target

Abstract Hypoxia-inducible factor 1α (HIF-1α) plays a crucial role in facilitating tumor progression and metastasis. Reducing the levels of HIF-1α might therefore be an important anticancer strategy. This could be achieved by understanding the key cellular events involved in HIF-1α activation. Present study explored the effect of phenethyl isothiocyanate (PEITC), a natural isothiocyanate, found in cruciferous vegetables on the expression of HIF-1α and HSP90 in breast adenocarcinoma cell lines (MCF-7 and MDA-MB-231) under both normoxia and hypoxia. This study established the possible role of ROS in the up-regulation of these markers in breast cancer cells. PEITC-induced nuclear accumulation of Nrf2, increased the activities of several antioxidant enzymes, and thus reduced the ROS burden of the tumor cells by acting as an indirect antioxidant. This resulted in the down-regulation of HSP90 and thereby HIF-1α expression. HSP90 was also found to be involved in the regulation of HIF-1α. A probable link between down-regulation of HIF-1α with reduction of ROS by PEITC through induction of Nrf2 was determined. Finally, our study demonstrated that modulation of HIF-1α by PEITC retarded adhesion, aggregation, migration and invasion of the breast cancer cells, thereby showing anti-metastatic effect. Activities of MMPs (2 & 9) and expression of VEGF were also altered by PEITC.

Inhibition of crosstalk between Bcr-Abl and PKC signaling by PEITC, augments imatinib sensitivity in chronic myelogenous leukemia cells.

Chronic myelogenous leukemia (CML), a clonal hyperproliferation of immature blood cells accounts for 20% of adult leukemia cases. Reciprocal translocation of chromosomes 9 and 22, results into Bcr-Abl fusion and is responsible for expression of a tyrosine kinase protein p210(bcr/abl), which mediates several survival pathways and confer therapeutic resistance. Protein kinase C (PKC), a family of serine threonine kinases play an important role in the process of leukemogenesis. A crosstalk between Bcr-Abl and PKC signaling has been documented. Therefore, targeting p210(bcr/abl) and its associated signaling proteins using non-toxic natural means will be an effective strategy for antileukemic therapy. Aim of the present study is to investigate whether PEITC, a natural isothiocyanate in combination with imatinib mesylate (IM), a tyrosine kinase inhibitor could increase the therapeutic efficacy of IM by modulating the expression of p210(bcr/abl). Enhanced cytotoxic efficacy of IM by PEITC was further validated using another myelogenous leukemia cell line, KU812. It was observed that PEITC in combination with IM efficiently downregulated the expression of p210(bcr/abl) in chronic myelogenous leukemia cell lines (K-562). PEITC inhibited the expressions of PKCα, PKCβII and PKCζ (both phosphorylated and total form). Expression of Raf1 and ERK1/2, two important target proteins in PKC signaling cascade was diminished. The result indicated that PEITC ultimately reduced expression of Raf1 and ERK1/2 through Bcr-Abl and PKC inhibition. This result was further confirmed by UCN-01, a selective PKC inhibitor and IM; indicating an association between p210(bcr/abl) and PKC with Raf1 and ERK1/2. PEITC thus may have enormous potential in synergistic therapy of leukemia by enhancing drug efficacy.

Curcumin Inhibits Histone Deacetylase Leading to Cell Cycle Arrest and Apoptosis via Upregulation of p21 in Breast Cancer Cell Lines

ABSTRACT Curcumin was reported to modulate the expression of HDACs 1 and 2. The effect of curcumin on the expression levels of acetylated histones (H3 and H4), acetylated p53, p21, cyclinB1, and Cdk-1 were investigated in breast cancer cell lines MCF-7 and MDA-MB-231, expressing wild-type and mutated p53, respectively. Curcumin increased histone acetylation in both cell lines. Increased p53 acetylation was observed in MCF-7 but not in MDA-MB-231. Upregulation of p21 by curcumin was observed in both cell lines, leading to cell cycle arrest and apoptosis by caspase-9 induction. Curcumin therefore may be regarded as a potent epigenetic regulator in breast cancer.

In Search of Natural Remediation for Cervical Cancer

Cancer is a serious global health issue. Cancer of the cervix is one of the leading gynecological malignancies worldwide; though it is more prevalent in the developing countries. Fruitful approaches are needed to control cervical cancer. Awareness through proper education, screening and early detection may pave a way to combat the disease process in the first place. Surgery, chemotherapy and radiotherapy are some of the common modes of treatment for cervical cancer. Conventional medical treatments often are not able to eliminate the offending growth fully and are not free from complications. Side effects very often are disastrous. Therefore, it is high time to focus our attention to bring about a novel way to tackle the problem. Advocating holistic approach using plant derived phytochemicals may address this health problem. These molecules show potent anticancer potential and are free from toxicity. Adjunctive therapies using phytochemicals may prove to be of tremendous importance. Plants are a prime source of effective drugs for the treatment of various forms of cancer. Many of these compounds are well characterized and have led the researchers to develop potential chemotherapeutic agents. Neutraceuticals may not replace the conventional treatment regimen, but they may enhance the efficacy of chemotherapy and radiotherapy.

Sulforaphane Inhibits Metastatic Events in Breast Cancer Cells through Genetic and Epigenetic Regulation

Metastasis is a deadly event in carcinogenesis, which is regulated both genetically as well as epigenetically. Regulation of key molecules involved in this phenomenon could be a promising strategy in cancer control. The epigenetic enzyme HDAC6 along with telomerase and HSP90, two genetic markers of carcinogenesis are implicated in the metastatic pathway. Therefore, modulation of these markers may aid in prevention of spread of cancer to distant parts. Plant derived molecules are apparently nontoxic and stud with anticancer activities. Present study aims to investigate the effect of sulforaphane (Sfn), an organosulfur compound on these markers, which might be helpful in inhibition of metastasis. It was observed that sulforaphane significantly inhibited HDAC6 expression, both at protein and genetic level in metastatic breast cancer cell MDA-MB-231. Inhibition of HDAC6 was associated with increased acetylation of HSP90 and diminished expression of transcription factor c-myc. These results were further confirmed by using tubacin, a specific HDAC6 inhibitor. Activity and expression of human telomerase reverse transcriptase, a main determinant of catalytic activity of the enzyme was found to be inhibited by Sfn. Repression of c-myc led to transcriptional down-regulation of hTERT mRNA and de-repression of p21. Modulation of these proteins led to down-regulation of VEGF and MMPs (2 and 9), two key players of the metastatic event. Regulation of these proteins by Sfn decelerates migration and invasion of the metastatic breast cancer cells, thereby showing anti-metastatic potential. Sulforaphane, by virtue of its modulatory role on HDAC6 and other associated proteins may lead to inhibition of metastasis in breast cancer cells.