RECK and TIMP-2 mediate inhibition of MMP-2 and MMP-9 by Annona muricata

Up-regulation of MMP-2 and MMP-9 plays a significant role in promoting cancer progression by degradingthe components of the extracellular matrix, thereby enhancing the migration of tumor cells. Although the antiproliferative and apoptotic effect of Annona muricata is well established, its effect on MMP-2 and MMP-9, amajor target in several types of cancers, has not been studied. Powdered samples of various parts of A.muricata like fruit, stem, seed, and twig extracted using aqueous methanol showed significant dose-dependentinhibition of MMP-2 and MMP-9 in a highly metastatic fibrosarcoma cell line, HT1080. Additionally, theseextracts also up-regulated the expression of several endogenous inhibitors of MMP-2 and MMP-9 likeREversion-inducing Cysteine-rich protein with Kazal motifs (RECK) and Tissue Inhibitor of Metalloproteinase-2 (TIMP-2). Furthermore, primary cells developed from tumor tissues obtained from patients notexposed to chemotherapy, also exhibited similar results. Remarkably, the inhibition of MMP-2 and MMP-9observed was tumor specific, with the A. muricata fruit extract showing only 2% inhibition in cells obtainedfrom normal tissues, when compared to 60% inhibition observed in cells obtained from tumor samples. Thepresent study elucidates a novel mechanism by which A. muricata extracts selectively exhibit their anti-canceractivity in tumor cells by down-regulating MMP-2 and MMP-9 that are important biomarkers in cancer.

Sensitization of hepatocellular carcinoma cells towards doxorubicin and sorafenib is facilitated by glucosedependent alterations in reactive oxygen species, P-glycoprotein and DKK4

Altered glucose uptake and metabolism is the key characteristic of cancer cells including hepatocellularcarcinoma (HCC). However, role of glucose availability in chemotherapeutic outcome of HCC is unclear. Thepresent study investigates the effect of glucose facilitated sensitization of HCC cells towards doxorubicin(DOX) and sorafenib (SORA). In HCC cells, we observed that hyperglycemic culture condition (HG) isassociated with increased sensitivity towards DOX and SORA. P-glycoprotein (P-gp), a transporter involved indrug efflux, was elevated in HCC cells in NG, rendering them less susceptible to DOX and SORA. Further, thisstudy demonstrated that knockdown of dickkopf protein 4 (DKK4), a Wnt antagonist protein, causes enhancedglucose uptake and reduction in P-gp level rendering HCC cells in NG sensitive to DOX and SORA.Moreover, HG elevates the level of intracellular reactive oxygen species (ROS), which regulates P-gp.Alteration in intracellular ROS did not directly affect regulation of DKK4 in HCC cells. Functional assayssuggest that alterations in DKK4 and P-gp level in HCC cells are dependent on glucose availability andchanges in ROS level because of enhanced glucose utilization, respectively. Collectively, the present studyhighlights direct involvement of glucose-induced ROS, DKK4 and P-gp in altering the sensitivity of HCC cellstowards DOX and SORA.