Synthetic Lethality by Lentiviral Short Hairpin RNA Silencing of Thymidylate Kinase and Doxorubicin in Colon Cancer Cells Regardless of the <i>p53</i> Status

Hu, Chunmei; Chang, Zee-Fen

doi:10.1158/0008-5472.can-07-3069

Cited by 24 publications

(19 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[25] However, in another study, repression of the TYMK gene by RNAi did not induce direct lethal consequences in human colon cancer cell lines. [20] Quantitative PCR results revealed that silencing of the TYMK gene by RNAi achieved a significant (P < 0.02) 4-fold reduction of TYMK expression in the tymk-shRNA cell lines compared to the value of control cell lines ( Figure 4A). To determine whether this reduction had any effect on expression levels of DUT, TK, DCTD, and TYMS genes, quantitative PCR measurements were performed to measure their mRNA levels in tymk-shRNA cells.…”

Section: Silencing Of the Tymk Gene And Its Effect On Expressions Of mentioning

confidence: 95%

“…[5,18,19] Efficient RNAi experiments were also reported to silence the TYMK and TYMS genes in colon cancer cell lines. [20] In the present study, we aimed at generation of stable HeLa cell lines in which either the DUT or the TYMK gene is constantly silenced by a vector-based RNAi system. With respect to the essential functions of the aforementioned enzymes in thymidylate metabolism, we aimed to characterize the gene expression pattern of DUT, TK, TYMK, DCTD, and TYMS enzymes as molecular responses to the gene silencing (cf.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Cellular Response to Efficient dUTPase RNAi Silencing in Stable HeLa Cell Lines Perturbs Expression Levels of Genes Involved in Thymidylate Metabolism

Merényi

Kovari

Tóth

et al. 2011

Nucleosides, Nucleotides & Nucleic Acids

View full text Add to dashboard Cite

Section: Silencing Of the Tymk Gene And Its Effect On Expressions Of mentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Cellular Response to Efficient dUTPase RNAi Silencing in Stable HeLa Cell Lines Perturbs Expression Levels of Genes Involved in Thymidylate Metabolism

Merényi

Kovari

Tóth

et al. 2011

Nucleosides, Nucleotides & Nucleic Acids

View full text Add to dashboard Cite

“…It was previously shown that reducing the cellular level of dTTP by silencing thymidylate kinase expression significantly sensitizes tumor cells to a chemotherapeutic agent, demonstrating the importance of dTTP supply in tumor cell survival after genotoxic insults (39). Importantly, blocking TS does not necessarily lead to chemosensitization unless thymidine is deprived from the culture medium (39). These findings prompt us to further investigate the functional contribution of TK1-mediated dTTP synthesis in DNA damage response.…”

mentioning

confidence: 97%

“…A number of studies have shown that the decrease in the dTTP level due to TK deficiency is correlated with the increase in DNA damage-in-duced cell death and mutagenesis (33)(34)(35)(36)(37)(38). It was previously shown that reducing the cellular level of dTTP by silencing thymidylate kinase expression significantly sensitizes tumor cells to a chemotherapeutic agent, demonstrating the importance of dTTP supply in tumor cell survival after genotoxic insults (39). Importantly, blocking TS does not necessarily lead to chemosensitization unless thymidine is deprived from the culture medium (39).…”

mentioning

confidence: 99%

Regulation and Functional Contribution of Thymidine Kinase 1 in Repair of DNA Damage

Chen

Eriksson

Chang

2010

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

Cellular supply of dNTPs is essential in the DNA replication and repair processes. Here we investigated the regulation of thymidine kinase 1 (TK1) in response to DNA damage and found that genotoxic insults in tumor cells cause up-regulation and nuclear localization of TK1. During recovery from DNA damage, TK1 accumulates in p53-null cells due to a lack of mitotic proteolysis as these cells are arrested in the G 2 phase by checkpoint activation. We show that in p53-proficient cells, p21 expression in response to DNA damage prohibits G 1 /S progression, resulting in a smaller G 2 fraction and less TK1 accumulation. Thus, the p53 status of tumor cells affects the level of TK1 after DNA damage through differential cell cycle control. Furthermore, it was shown that in HCT-116 p53 ؊/؊ cells, TK1 is dispensable for cell proliferation but crucial for dTTP supply during recovery from DNA damage, leading to better survival. Depletion of TK1 decreases the efficiency of DNA repair during recovery from DNA damage and generates more cell death. Altogether, our data suggest that more dTTP synthesis via TK1 take place after genotoxic insults in tumor cells, improving DNA repair during G 2 arrest.The synthesis of dTTP is highly regulated and is important for DNA replication and repair in all living cells (1, 2). There are two pathways for dTTP synthesis in cells. In the de novo pathway, ribonucleotide reductase, which is composed of two pairs of R1 and R2 subunits, converts CDP and UDP to dCDP and dUDP, respectively. Both dCDP and dUDP can be metabolically converted to dUMP, and thymidylate synthase (TS) 3 catalyzes the reaction of dTMP formation from dUMP. In the salvage pathway, thymidine kinases (TKs), TK1 in cytosol and TK2 in mitochondria (3, 4), are responsible for dTMP production from thymidine (5). Phosphorylation of dTMP from either the salvage or de novo pathway to dTDP is catalyzed by thymidylate kinase, and nucleoside diphosphate kinase then converts dTDP to dTTP (6). Unlike TK2, the expression of TK1, TS, and thymidylate kinase is cell cycle-dependent (7-13).In response to DNA damage, cells trigger multifaceted responses such as cell cycle arrest, DNA repair, or apoptosis (14, 15). In Saccharomyces cerevisiae, it has been reported that DNA damage by ␥-irradiation, UV, or methyl methane sulfonate leads to increases in the levels of the four dNTPs through ribonucleotide reductase-mediated de novo synthesis, indicating a close relationship between the regulation of dNTP synthesis and DNA damage response (16,17). In mammalian cells, expression of p53-inducible R2 (p53R2), a homolog of the R2 subunit, is increased due to p53-dependent transcriptional activation upon DNA damage, suggesting a master role of p53 in integrating regulation of dNTP pools through the de novo pathway (18 -21). However, it is known that more than 50% human cancer cells harbor mutated or deleted p53, and these tumors are more resistant to chemotherapy due to the loss of p53-dependent apoptosis (22,23). This evoked the question as how p53-deficie...

show abstract

“…We have previously deciphered, at least partly, how ISP induces apoptosis in the human HCT-116 colon cancer cells (9), which displays sensitivity to pro-apoptotic stimuli (24,25). ISP induces apoptosis in HCT-116 colon cancer cells as shown by the translocation of phosphatidylserine from the inner layer to the outer layer of the plasma membrane, chromatin condensation, DNA fragmentation, and caspase-3 and -9 activation (9).…”

Section: Discussionmentioning

confidence: 99%

Isostrychnopentamine, an indolomonoterpenic alkaloid from Strychnos usambarensis, with potential anti-tumor activity against apoptosis-resistant cancer cells

Baldé

Mégalizzi²,

Cao³

et al. 2010

Int J Oncol

View full text Add to dashboard Cite

Abstract. Isostrychnopentamine (ISP) is an indolomonoterpenic alkaloid that is present in the leaves of Strychnos usambarensis, an East African small tree. We have reported previously pro-apoptotic effects induced in vitro by ISP in the human HCT-116 colon cancer cell line, a model that displays relative sensitivity to apoptosis. In the present study, we observed that the in vitro growth inhibitory activities of ISP are similar in cancer cells that display sensitivity versus resistance to apoptosis. We made use of the U373 glioblastoma and the A549 non-small cell lung cancer (NSCLC) cell lines as models relatively resistant to apoptosis, and the human PC-3 prostate cancer cell line as a model relatively sensitive to apoptosis. While ISP induced transient decreases in [ATP] i and apoptosis in human U373 GBM cells, it did not provoke such features in A549 NSCLC cells. It thus seems that ISPinduced anti-cancer activity can lead to pro-apoptotic effects as a consequence, while apoptosis seems not to be the main cause by which ISP induces cancer cell death. ISP is a compound that merits further investigations in order to: i) identify the mechanism(s) of action by which it kills cancer cells, and ii) hemisynthesize novel ISP derivatives aiming to overcome, at least partly, the resistance of metastatic cancers to apoptosis. IntroductionDespite frequent responses to chemotherapy, curative treatment remains elusive for the majority of patients with metastatic solid tumors (1). Indeed, in the common advanced cancers, over 40 years of cytotoxic drug development has brought no significant change in cure rates (1). Savage and colleagues (1) report that one interpretation is that the intrinsic properties of the malignancies themselves, rather than the qualities of individual drugs or combination therapies, are primarily responsible for their curability with chemotherapy. These authors thus suggest that the curability of these malignancies results from an intrinsic 'locked-in' state of sensitivity to proapoptotic stresses in these cells (1). In fact, >90% of cancer patients die from their metastases (2). Drug resistance, either acquired or intrinsic, often prevents tumor cells from undergoing sufficient levels of apoptosis, resulting in cancer cell survival and treatment failure (1,2). The metastatic process is inherent to a significant level of resistance to apoptosis. Indeed, as a barrier to metastases, cells normally undergo apoptosis after they lose contact with their extra cellular matrix or their neighboring cells (3). This cell death process has been termed 'anoikis' (3). Tumor cells that acquire malignant potential have developed mechanisms to resist anoikis and thereby survive after detachment from their primary site and while travelling through the lymphatic and circulatory systems (3). Defects in the death receptor pathway of caspase activation, such as the over-expression of the caspase-8 inhibitor FLIP, can render cells resistant to anoïkis (3).Plants have played a dominant role in the development of sophisticate...

show abstract

Synthetic Lethality by Lentiviral Short Hairpin RNA Silencing of Thymidylate Kinase and Doxorubicin in Colon Cancer Cells Regardless of the p53 Status

Cited by 24 publications

References 31 publications

Cellular Response to Efficient dUTPase RNAi Silencing in Stable HeLa Cell Lines Perturbs Expression Levels of Genes Involved in Thymidylate Metabolism

Cellular Response to Efficient dUTPase RNAi Silencing in Stable HeLa Cell Lines Perturbs Expression Levels of Genes Involved in Thymidylate Metabolism

Regulation and Functional Contribution of Thymidine Kinase 1 in Repair of DNA Damage

Isostrychnopentamine, an indolomonoterpenic alkaloid from Strychnos usambarensis, with potential anti-tumor activity against apoptosis-resistant cancer cells

Contact Info

Product

Resources

About