Knockdown of protein phosphatase 5 inhibits ovarian cancer growth in vitro

Abstract

Abstract. Ovarian cancer is the most common cause of gynecological cancer-related mortality. Serine/threonine protein phosphatase 5 (PP5, PPP5C) has been recognized to be involved in the regulation of multiple cellular signaling cascades that control diverse cellular processes, including cell growth, differentiation, proliferation, motility and apoptosis. In this study, to evaluate the functional role of PP5 in ovarian cancer cells, lentivirus-mediated RNA interference (RNAi) was applied to silence PPP5C in the human ovarian cancer cell line CAOV-3. Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell colony forming ability was measured by colony formation. Cell cycle progression was determined by propidium iodide staining and flow cytometry. The results demonstrated that lentivirus-mediated RNAi specifically suppressed the expression of PPP5C at the mRNA and protein levels in CAOV-3 cells. Further investigations revealed that PP5 knockdown significantly inhibited the proliferation and colony formation of CAOV-3 cells. Moreover, the cell cycle of CAOV-3 cells was arrested at the G0/G1 phase following PP5 knockdown. This study highlights the crucial role of PP5 in promoting ovarian cancer cell proliferation, and provides a foundation for further study into the clinical potential of lentiviral-mediated delivery of PP5 RNAi therapy for the treatment of ovarian cancer. IntroductionOvarian cancer is the most common invasive malignancy of the female genital tract in the USA, with an estimated 22,240 cases diagnosed annually. Approximately 14,030 females succumb every year to ovarian cancer, representing the most common cause of mortality among females with gynecological malignancies (1). Surgical resection and platinum-based combination regimens offer a modest but significant survival advantage in ovarian cancer patients with advanced or metastatic disease, although most patients eventually experience disease progression (2). These data highlight the need to identify new approaches that, along with the current treatments, may assist in bringing about a better outcome for ovarian cancer patients.Protein kinases and phosphatases work together to control cellular processes and signaling pathways (3,4). Although much more is known about protein kinases and their relevant substrates compared with protein phosphatases (5-7), the significance of studying protein phosphatase enzymes and their targets has been demonstrated for disease states attributed in part to malfunctioning protein phosphatase enzymes (8). Protein phosphatase 5 (PP5; gene name, PPP5C) is a ubiquitously expressed serine/threonine protein phosphatase related to PP1, PP2A and PP2B (9). Structural analysis has revealed that PP5 contains a C-terminal catalytic domain and three N-terminal tetratricopeptide repeats (TPRs) that are unique in the phosphoprotein phosphatase family (10). PP5 is auto-inhibited by intramolecular interactions with its TPR domain (11).PP5 has been implicated in numerous cellular processe...

MiR-20a-5p functions as a potent tumor suppressor by targeting PPP6C in acute myeloid leukemia

“…The pro-survival effects of PPP6C have been manifested in ultraviolet-B-induced carcinogenesis [ 22 ] and keratinocyte proliferation [ 23 ]. By searching the members of the protein serine/threonine phosphatase family, we found PPP5C could significantly promote the tumor cell proliferation and survival, including HCC [ 34 ], ovarian cancer [ 35 ] and prostate cancer [ 36 ]. Interestingly, knockdown of PPP5C suppressed the proliferation ability, and led to G0/G1 phase arrest, induced cell apoptosis in leukemic cell line U937 cells [ 37 ], which is line with our data showed that PPP6C promoting AML cell proliferation.…”

PPP5C promotes cell proliferation and survival in human prostate cancer by regulating of the JNK and ERK1/2 phosphorylation

“… 18 Several subsequent studies 19 – 21 also reported that PPP5C was upregulated in breast cancer, mantle-cell lymphoma and liver cancer tissues, and ascites. Other studies 22 – 25 reported that downregulation of PPP5C expression could inhibit malignant cells in human glioma, ovarian cancer, hepatocellular carcinoma, and colorectal cancer. The aforementioned findings suggest that PPP5C may play a role in the development and progression of some cancers.…”

The Antitumor Drug LB-100 Is a Catalytic Inhibitor of Protein Phosphatase 2A (PPP2CA) and 5 (PPP5C) Coordinating with the Active-Site Catalytic Metals in PPP5C

“…Because inactivating alterations of PP2A subunits have been observed in human cancers and the suppression of the same PP2A components contribute to cell transformation (for review, see ref, 29), many view PP2A as a tumor suppressor. In contrast, PPP5C is found in high levels in several types of human cancers (30)(31)(32)(33)(34)(35), and many lines of evidence indicate that inhibitors of PPP5C may prove useful for the medical management of several types of human cancers (30,32,(36)(37)(38)(39)(40)(41)(42)(43). Therefore, when several carboxamide derivatives containing the 7-oxabicyclo[2.2.1]heptane-2-carboxylic acid moiety shared with LB-100 were identified as novel inhibitors of PPP5C in an ultra-high-throughput screening campaign (44), we were prompted to test LB-100 for inhibitory activity against PPP5C.…”