Reexpression of Tumor Suppressor, sFRP1, Leads to Antitumor Synergy of Combined HDAC and Methyltransferase Inhibitors in Chemoresistant Cancers

Abstract

Metastatic solid tumors are aggressive and mostly drug resistant leading to few treatment options and poor prognosis as seen with clear cell renal cell carcinoma (ccRCC) and triple negative breast cancer (TNBC). Therefore the identification of new therapeutic regimes for the treatment of metastatic disease is desirable. ccRCC and TNBC cell lines were treated with the HDAC inhibitor romidepsin and the methyltransferase inhibitor decitabine, two epigenetic modifying drugs approved by the FDA for the treatment of various hematologic malignancies. Cell proliferation analysis, flow cytometry, quantitative PCR and immuno-blotting techniques were utilized to evaluate the antitumor synergy of this drug combination and identify the re-expression of epigenetically silenced tumor suppressor genes. Combinatorial treatment of metastatic TNBC and stage 4 ccRCC cell lines with romidepsin/decitabine leads to synergistic inhibition of cell growth and induction of apoptosis above levels of individual drug treatments alone. Synergistic re-expression of the tumor suppressor gene secreted frizzled-related protein one (sFRP1) was observed in combinatorial drug treated groups. Silencing sFRP1 (shRNA) prior to combinatorial drug treatment demonstrated that sFRP1 mediates the growth inhibitory and apoptotic activity of combined romidepsin/decitabine. Furthermore, addition of recombinant sFRP1 to ccRCC or TNBC cells inhibits cell growth in a dose-dependent manner through the induction of apoptosis identifying that epigenetic silencing of sFRP1 contributes to renal and breast cancer cell survival. Combinatorial treatment with romidepsin and decitabine in drug resistant tumors is a promising treatment strategy. Moreover, recombinant sFRP1 may be a novel therapeutic strategy for cancers with suppressed sFRP1 expression.

MicroRNA-27a Promotes the Proliferation and Invasiveness of Colon Cancer Cells by Targeting SFRP1 through the Wnt/β-Catenin Signaling Pathway

“…Cell proliferation and anchorage independent growth can be inhibited if miR-27a is suppressed, which demonstrates that miR-27a exerts effects on cell proliferation [30]. The tumor suppressor gene SFRP1 functions as a negative regulator of Wnt signaling via its ability to form a heterodimer with Frizzled; this then prevents the formation of nonfunctional receptor complexes by Wnt proteins [31]. As Wnt antagonists, proteins in the SFRP family are endogenous modulators of Wnt signaling that compete with Wnt ligands for binding to the Frizzled receptors.…”

[Retracted Article] Methylation of the Wnt Signaling Antagonist, Wnt Inhibitory Factor 1 and Dickkopf-1 Genes in Acute Myeloid Leukemia at the Time of Diagnosis

“…Epigenetic disorders, in contrast to genetic changes, are reversible and a role of the DNA demethylating agents such as 5-aza-2'-deoxycytidine has been established in the treatment of hematopoietic malignancies [3][4][5][6]. Cooper et al suggested that recombinant SFRP may be a novel therapeutic strategy for cancers with suppressed SFRP expression [25]. The DKK-1 gene, located on chromosome 11p15.1, is suppressed in a difference of human cancer cell lines and in numerous kinds of human cancers such as non-small cell lung carcinomas [26,27], human renal clear cell carcinoma [26], acute lymphoblastic leukemia [28] which also makes it a candidate tumor suppressor gene.…”

Low SFRP1 Expression Correlates with Poor Prognosis and Promotes Cell Invasion by Activating the Wnt/β-Catenin Signaling Pathway in NPC

“…SFRP1 hypermethylation and downregulation are also associated with poor prognosis in several tumors (34,37,38). Moreover, SFRP1 is associated with tumor chemotherapy, and some antitumor drugs inhibit cell growth through the re-expression of SFRP1 (39)(40)(41). However, emerging evidence has indicated that SFRP1 may also be highly expressed in carcinomas and promote tumor proliferation or migration, such as in basal-like breast cancer (42), gastric cancer (43), and metastatic renal carcinoma (44).…”