A PARP1 PROTAC as a novel strategy against PARP inhibitor resistance via promotion of ferroptosis in p53-positive breast cancer.

Therapeutic targeting of the nuclear enzyme poly (ADP-ribose) polymerase 1 (PARP1) with PARP inhibitors (PARPis) in patients with a homologous recombination (HR)- deficient phenotype based on the mechanism of synthetic lethality has been shown tremendous success in cancer therapy. With the clinical use of various PARPis, emerging evidence has shown that some PARPis offer hope for breakthroughs in triple-negative breast cancer (TNBC) therapy, regardless of HR status. However, similar to other conventional cytotoxic drugs, PARPis are also subject to the intractable problem of drug resistance. Notably, acquired resistance to PARPis caused by point mutations in the PARP1 protein is hard to overcome with current strategies. To explore modalities to overcome resistance and identify patients who are most likely to benefit from PARP1-targeted therapy, we developed a proteolysis-targeted chimaera (PROTAC) to degrade mutant PARP1 in TNBC. Here, we investigated a PARP1 PROTAC termed "NN3″, which triggered ubiquitination and proteasome-mediated degradation of PARP1. Moreover, NN3 degraded PARP1 with resistance-related mutations. Interestingly, compared with other reported PARP1 degraders, NN3 exhibited a unique antitumor mechanism in p53-positive breast cancer cells that effectively promoted ferroptosis by downregulating the SLC7A11 pathway. Furthermore, NN3 showed potent activity and low toxicity in vivo. In conclusion, we propose PROTAC-mediated degradation of PARP1 as a novel strategy against mutation-related PARPi resistance and a paradigm for targeting breast cancer with functional p53 via ferroptosis induction.

The microRNA miR-184 regulates the CYP303A1 transcript level to control molting of Locusta migratoria.

Cytochrome P450 monooxygenases (CYPs) play essential physiological functions in insects. CYP303A1 is highly conserved in insect species studied to date, and shows an indispensable role for adult eclosion in both Locusta migratoria and Drosophila melanogaster. However, how CYP303A1 is regulated to control insect developmental processes remains uninvestigated. In this study, we discovered functional binding sites for miR-184 in the coding sequence of LmCYP303A1. The luciferase reporter assay showed that miR-184 could target LmCYP303A1 and regulate its expression in vitro. Furthermore, overexpression of miR-184 through microinjection of agomir to locusts reduced the transcripts of LmCYP303A1 and led to abnormal molting, which is similar to the phenotype of silencing LmCYP303A1 by direct injection of dsLmCYP303A1 to locusts. Meanwhile, down-regulation of miR-184 by injection of antagomir increased the LmCYP303A1 transcript and caused molting defects. These findings suggested that miR-184 could target LmCYP303A1 to regulate the molting process in L. migratoria, which might be considered as a novel target for pest control.

Curcumin derivative C817 inhibits proliferation of imatinib-resistant chronic myeloid leukemia cells with wild-type or mutant Bcr-Abl in vitro.

AIM: To find new kinase inhibitors that overcome the imatinib resistance in treatment of chronic myeloid leukemia (CML), we synthesized C817, a novel derivative of curcumin, and tested its activities against wild-type (WT) and imatinib-resistant mutant Abl kinases, as well as in imatinib-sensitive and resistant CML cells in vitro. METHODS: 32D cells harboring WT or mutant Abl kinases (nucleotide binding P-loop mutants Q252H, Y253F, and imatinib contact residue mutant T315I), as well as K562/G01 cells (with whole Bcr-Abl gene amplication) were tested. Kinase activity was measured using Kinase-Glo Luminescent Kinase Assay Platform in recombinant WT and mutant (Q252H, Y253F, and T315I) Abl kinases. Cell proliferation and apoptosis were examined using MTT assay and flow cytometry, respectively. The phosphorylation levels of Bcr-Abl initiated signaling proteins were analyzed using Western blotting. Colony forming units (CFU) growth and long term culture-initiating cells (LTC-ICs) were used to test the effects of C817 on human leukemia progenitor/stem cells. RESULTS: C817 potently inhibited both WT and mutant (Q252H, Y253F, and T315I) Abl kinase activities in a non-ATP competitive manner with the values of IC50 at low nanomole levels. In consistent with above results, C817 suppressed the growth of both imatinib-sensitive and resistant CML cells, including wild-type K562, K562/G01, 32D-T315I, 32D-Q252H, and 32D-Y253F cells with the values of IC50 at low micromole levels. C817 (0.5 or 1 µmol/L) dose-dependently inhibited the phosphorylation of Bcr-Abl and downstream proteins STAT-5 and CrkL in imatinib-resistant K562/G01 cells. Furthermore, C817 significantly suppressed CFU growth and LTC-ICs, implicating that C817 could eradiate human leukemia progenitor/stem cells. CONCLUSION: C817 is a promising compound for treatment of CML patients with Bcr-Abl kinase domain mutations that confer imatinib resistance.

Metabolic engineering for ethylene production by inserting the ethylene-forming enzyme gene (efe) at the 16S rDNA sites of Pseudomonas putida KT2440.

The ethylene-forming enzyme gene (efe) from Pseudomonas syringae pv. glycinea was transferred into Pseudomonas putida KT2440 by recombination at five of the seven 16S rDNA sites. PCR analysis demonstrated that strains DC1, DC2 and DC3 contained three, four and five copies of efe, respectively. In contrast to the parent strain which produced ethylene at 14.7 mg h(-1) g(-1) dry weight, strains DC1, DC2 and DC3 produced ethylene at 36.2, 47.2 and 53.8 mg h(-1) g(-1) dry weight, respectively. Quantitative PCR showed that efe mRNA levels increased with increasing efe copy numbers. When additional copies of efe were introduced into strain DC3 via the broad-host-range plasmid pBBR1MCS2 an ethylene production rate of 80.2 mg h(-1) g(-1) dry weight was obtained and 489 mg ethylene was produced in 24h corresponding to a conversion rate of 21.7 mg ethylene g(-1) glucose. Our results indicated that P. putida KT2440 could be genetically modified to be a promising biomaterial producer.

Curcumin synergistically augments bcr/abl phosphorothioate antisense oligonucleotides to inhibit growth of chronic myelogenous leukemia cells.

AIM: To investigate the growth inhibition effect of the combination of bcr/abl phosphorothioate antisense oligonucleotides (PS-ASODN) and curcumin (cur), and the possible mechanisms of cur on the chronic myelogenous leukemia cell line K562. METHODS: The K562 cell line was used as a P210( bcr/abl )-positive cell model in vitro and was exposed to different concentrations of PS-ASODN (0-20 micromol/L), cur (0-20 micromol/L), or a combination of both. Growth inhibition and apoptosis of K562 cells were assessed by MTT assay and AO/EB fluorescent staining, respectively. The expression levels of P210( bcr/abl ), NF-kappaB and heat shock protein 90 (Hsp90) were assessed by Western blot. RESULTS: Exposure to cur (5-20 micromol/L) and PSASODN (5-20 micromol/L) resulted in a synergistic inhibitory effect on cell growth. Growth inhibition was associated with the inhibition of the proliferation and induction of apoptosis. Western blot analysis showed that the drugs synergistically downregulated the level of P210( bcr/abl ) and NF-kappaB. Cur downregulated Hsp90, whereas no synergism was observed when cur was combined with PS-ASODN. CONCLUSION: PS-ASODN and cur exhibited a synergistic inhibitory effect on the cell growth of K562. The synergistic growth inhibition was mediated through different mechanisms that involved the inhibition of P210( bcr/abl ).

[Construction of hyaluronidase gene mutant of Enterococcus faecium and the function of hyaluronidase gene].

OBJECTIVE: To construct a hyaluronidase (hyl) gene mutant strain of Enterococcus faecium and to study the function of hyl gene. METHODS: An isogenic hyl-deficient mutant (*hyl) with suicide plasmid pTX4577 was constructed and screened by allelic replacement. The mutant strain and wild type strain TX2466 were cultured to observe the growth curves. Both *hyl and TX2466 strains were cultured in solid with kanamycin (KAN) to detect the tolerance to KAN. The study of virulence in mice peritonitis and rabbit endocarditis models in vivo were made. RESULTS: A mutant strain, *hyl, was selected by KAN and identified by PCR, pulsed field gel electrophoresis, and Southern blotting. The growth ability of the *hyl strain was remarkably reduced in comparison with the wide-type strain. The survival rate of the mice within 100 h after the inoculation of Enterococcus faecium. TX2466 was 0, significantly lower than that of the *hyl group (50%, P<0.01). The numbers of colonies in the aortic valve and ventricular wall vegetations of the TX2466 group rabbits were (3.04+/-0.63)x10(6) and (6.87+/-0.58)x10(6) CFU/g respectively, both significantly higher than those of the *hyl group [(0.21+/-0.06)x10(6) and (0.66+/-0.05)x10(6) CFU/g respective, both P<0.01]. CONCLUSION: Probably a major virulence factor of Enterococcus faecalis, hyl gene is important in the pathogenesis of this bacterium.

Down-regulation of p210(bcr/abl) by curcumin involves disrupting molecular chaperone functions of Hsp90.

AIM: To investigate the effects of curcumin (Cur) on p210(bcr/abl) level in K562 cells, and the relationship between these effects and the molecular chaperone functions of heat shock protein 90 (Hsp90). METHODS: Flow cytometry and Western blot were used to examine the abundance of p210(bcr/abl), Hsp90, p23, Hsp70, and p60(Hop) in K562 cells treated with Cur. Reverse transcription polymerase chain reaction (RT-PCR) was used to determine the bcr-abl mRNA level in K562 cells treated with Cur. After co-immunoprecipitation of p210(bcr/abl) and its molecular chaperones, the immunoprecipitate was then subjected to Western blot analysis with anti-Hsp90, anti-Hsp70, anti-p23, and anti- p60(Hop)mAb. RESULTS: An exposure of K562 cells to Cur produced time-dependent down-regulation of p210(bcr/abl), the inhibition rate of p210(bcr/abl) in K562 cells determined by flow cytometry after treatment with Cur 27.2 micromol/L for 1 h, 6 h, 12 h and 24 h was 31.2%, 63.7%, 81.3% and 94.5%, respectively. In contrast, Cur had almost no influence on bcr-abl mRNA level. Treatment with Cur for 24 h reduced the association of p210(bcr/abl) with Hsp90/p23 complex, while increasing the association of p210(bcr/abl) with Hsp70/ p60(Hop) complex; however, the total protein abundance of Hsp90, p23, and p60(Hop) in K562 cells had no apparent change, while Hsp70 increased greatly. CONCLUSION: Down-regulation of p210(bcr/abl) by Cur involves dissociating the binding of p210(bcr/abl) with Hsp90/p23 complex. In contrast, the association of p210(bcr/abl) with Hsp70/ p60(Hop) complex increased.

Inhibitory effect of curcumin on proliferation of K562 cells involves down-regulation of p210(bcr/abl) initiated Ras signal transduction pathway.

AIM: To investigate the effects of curcumin (Cur) on proliferation of K562 cells and the relationship between these effects and Ras signal transduction pathway activated by p210bcr/abl. METHODS: K562 cell line was used as a p210bcr/abl-positive cell system and HL-60 cell line as a p210bcr/abl-negative control; etoposide (VP-16), which has no influence on p210bcr/abl and has resistance to K562 cells[1], was used as an anticancer drug control to compare with curcumin. MTT was used to determine the proliferative effects of drugs on K562 and HL-60 cells. Western blot and flow cytometry were used to examine the abundance of signal protein molecules expressed in tumor cells. RESULTS: An exposure of K562 cells or HL-60 cells to Cur produced both concentration- and time-dependent increase in the anti-proliferative rate. Moreover, both cell lines had the same sensitivity to Cur (P>0.05). In contrast, HL-60 cells had more sensitivity to VP-16 than K562 cells in anti-proliferative effect (P<0.01). The abundance of p210bcr/abl as well as MEK-1 and c-JUN proteins were strongly down-regulated in curcumin-treated p210bcr/abl-positive K562 cells while c-JUN and MEK-1 proteins were only slightly down-regulated in p210bcr/abl-negative HL-60 cells. CONCLUSION: Curcumin inhibited the proliferation of K562 cells and the inhibitory effect was correlated with down-regulation of the abundance of p210bcr/abl, which may ultimately lead to retard the Ras signal transduction pathway. Curcumin might be worthy of being evaluated as a potential chemotherapeutic agent to CML.