The two faces of FBW7 in cancer drug resistance

Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
BioEssays (Impact Factor: 4.73). 11/2011; 33(11):851-9. DOI: 10.1002/bies.201100101
Source: PubMed


Chemotherapy is an important therapeutic approach for cancer treatment. However, drug resistance is an obstacle that often impairs the successful use of chemotherapies. Therefore, overcoming drug resistance would lead to better therapeutic outcomes for cancer patients. Recently, studies by our own and other groups have demonstrated that there is an intimate correlation between the loss of the F-box and WD repeat domain-containing 7 (FBW7) tumor suppressor and the incurring drug resistance. While loss of FBW7 sensitizes cancer cells to certain drugs, FBW7-/- cells are more resistant to other types of chemotherapies. FBW7 exerts its tumor suppressor function by promoting the degradation of various oncoproteins that regulate many cellular processes, including cell cycle progression, cellular metabolism, differentiation, and apoptosis. Since loss of the FBW7 tumor suppressor is linked to drug resistance, FBW7 may represent a novel therapeutic target to increase drug sensitivity of cancer cells to conventional chemotherapeutics. This paper thus focuses on the new functional aspects of FBW7 in drug resistance.


Available from: Fukushima Hidefumi
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    • "Recently, multiple new targets of FBW7 including MED13 (Mediator 13), KLF2 (Krüppel-like factor 2), NF-κB2 [47, 48], and G-CSFR (Granulocyte colony stimulating factor receptor) [49] have been also discovered. Since several excellent review articles have already summarized the roles of FBW7 in human cancers [20, 22, 50, 51], we will briefly discuss these newly identified FBW7 substrates that would help us to further understand the critical role of FBW7 in tumorigenesis. "
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    ABSTRACT: FBW7 (F-box and WD repeat domain-containing 7) or Fbxw7 is a tumor suppressor, which promotes the ubiquitination and subsequent degradation of numerous oncoproteins including Mcl-1, Cyclin E, Notch, c- Jun, and c-Myc. In turn, FBW7 is regulated by multiple upstream factors including p53, C/EBP-δ, EBP2, Pin1, Hes-5 and Numb4 as well as by microRNAs such as miR-223, miR-27a, miR-25, and miR-129-5p. Given that the Fbw7 tumor suppressor is frequently inactivated or deleted in various human cancers, targeting FBW7 regulators is a promising anti-cancer therapeutic strategy.
    Oncotarget 04/2014; 5(8):2000-2015. DOI:10.18632/oncotarget.1859 · 6.36 Impact Factor
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    • "Fbw7 deficiency is thought to be involved in drug resistance in human cancers [22], [23]. It has been shown to be inactivated by mutation, deletion, or promoter hypermethylation in breast cancer [17], [18], colon cancer [19], [20], and leukemia [21]. "
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    ABSTRACT: Wogonin is a plant monoflavonoid which has been reported to inhibit cell growth and/or induce apoptosis in various tumors. The present study examined the apoptosis-inducing activity and underlying mechanism of action of wogonin in A549 cells. The results showed that wogonin was a potent inhibitor of the viability of A549 cells. Apoptotic protein changes detected after exposure to wogonin included decreased XIAP and Mcl-1 expression, increased cleaved-PARP expression and increased release of AIF and cytotchrome C. Western blot analysis showed that the activity of c-Myc/Skp2 and HDAC1/HDAC2 pathways, which play important roles in tumor progress, was decreased. Quantitative PCR identified increased levels of c-Myc mRNA and decreased levels of its protein. Protein levels of Fbw7α, GSK3β and Thr58-Myc, which are involved in c-Myc ubiquitin-dependent degradation, were also analyzed. After exposure to wogonin, Fbw7α and GSK3β expression decreased and Thr58-Myc expression increased. However, MG132 was unable to prevent c-Myc degradation. The present results suggest that wogonin has multiple anti-cancer effects associated with degradation of c-Myc, SKP2, HDAC1 and HDAC2. Its ability to induce apoptosis independently of Fbw7α suggests a possible use in drug-resistance cancer related to Fbw7 deficiency. Further studies are needed to determine which pathways are related to c-Myc and Fbw7α reversal and whether Thr58 phosphorylation of c-Myc is dependent on GSK3β.
    PLoS ONE 11/2013; 8(11):e79201. DOI:10.1371/journal.pone.0079201 · 3.23 Impact Factor
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    • "Fbxw7 has been identified as a p53 target gene [11,12]. In support of this notion, Fbxw7 was dramatically up-regulated by infection with adenovirus-mediated transfer of wild-type p53 into the p53-deficient cells [4]. Moreover, p53-binding sites were discovered in the Fbxw7 exon, further emphasizing Fbxw7 as a direct target of p53 [11]. "
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    ABSTRACT: F-box and WD repeat domain-containing 7 (Fbxw7/hAgo/hCdc4/Fbw7) is a p53-dependent tumor suppressor and leads to ubiquitination-mediated suppression of several oncoproteins including c-Myc, cyclin E, Notch, c-Jun and others. Our previous study has indicated that low expression of Fbxw7 was negatively correlated with c-Myc, cyclin E and mutant-p53 in hepatocellular carcinoma (HCC) tissues. But the role and mechanisms of Fbxw7 in HCC are still unknown. Here, we investigated the function of Fbxw7 in HCC cell lines and the anti-tumor activity of recombinant human adenovirus-p53 injection (rAd-p53, Gendicine) administration in vitro and in vivo. Fbxw7-specific siRNA enhanced expression of c-Myc and cyclin E proteins and increased proliferation in cell culture. rAd-p53 inhibited tumor cell growth with Fbxw7 upregulation and c-Myc and cyclin E downregulation in vitro and a murine HCC model. This effect could be partially reverted using Fbxw7-specific siRNA. Here, we suggest that the activation of Fbxw7 by adenoviral delivery of p53 leads to increased proteasomal degradation of c-Myc and cyclin E enabling growth arrest and apoptosis. Addressing this pathway, we identified that rAd-p53 could be a potential therapeutic agent for HCC.
    PLoS ONE 07/2013; 8(7):e68574. DOI:10.1371/journal.pone.0068574 · 3.23 Impact Factor
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