A Novel Inhibitor of Poly(ADP-Ribose) Polymerase-1 Inhibits Proliferation of a BRCA-Deficient Breast Cancer Cell Line via the DNA Damage-Activated cGAS-STING Pathway.

Loss-of-function mutations in the Breast Cancer Susceptibility Gene (BRCA1 and BRCA2) are often detected in patients with breast cancer. Poly(ADP-ribose) polymerase-1 (PARP1) plays a key role in the repair of DNA strand breaks, and PARP inhibitors have been shown to induce highly selective killing of BRCA1/2-deficient tumor cells, a mechanism termed synthetic lethality. In our previous study, a novel PARP1 inhibitor─(E)-2-(2,3-dibromo-4,5-dimethoxybenzylidene)-N-(4-fluorophenyl) hydrazine-1-carbothioamide (4F-DDC)─was synthesized, which significantly inhibited PARP1 activity with an IC50 value of 82 ± 9 nM. The current study aimed to explore the mechanism(s) underlying the antitumor activity of 4F-DDC under in vivo and in vitro conditions. 4F-DDC was found to selectively inhibit the proliferation of BRCA mutant cells, with highly potent effects on HCC-1937 (BRCA1-/-) cells. Furthermore, 4F-DDC was found to induce apoptosis and G2/M cell cycle arrest in HCC-1937 cells. Interestingly, immunofluorescence and Western blot results showed that 4F-DDC induced DNA double strand breaks and further activated the cGAS-STING pathway in HCC-1937 cells. In vivo analysis results revealed that 4F-DDC inhibited the growth of HCC-1937-derived tumor xenografts, possibly via the induction of DNA damage and activation of the cGAS-STING pathway. In summary, the current study provides a new perspective on the antitumor mechanism of PARP inhibitors and showcases the therapeutic potential of 4F-DDC in the treatment of breast cancer.

Excavatolide C/cisplatin combination induces antiproliferation and drives apoptosis and DNA damage in bladder cancer cells.

Excavatolide C (EXCC), a marine coral-derived compound, exhibits an antiproliferation effect on bladder cancer cells. The present study evaluated the improvement in the antiproliferation ability of EXCC by co-treatment with cisplatin in bladder cancer cells. EXCC/cisplatin (12.5 and 1 µg/mL) showed higher antiproliferation effects on bladder cancer cells than single treatments (EXCC or cisplatin alone) in the 48 h ATP assay. EXCC/cisplatin also enhanced the increase in subG1, annexin V-mediated apoptosis, and activation of poly (ADP-ribose) polymerase (PARP) and several caspases (caspases 3, 8, and 9) compared to the single treatments. Cellular and mitochondrial oxidative stress was enhanced with EXCC/cisplatin compared to the single treatments according to analyses of reactive oxygen species (ROS), mitochondrial superoxide, and mitochondrial membrane potential; in addition, cellular antioxidants, such as glutathione (GSH), and the mRNA expressions of antioxidant signaling genes (catalase and NFE2-like bZIP transcription factor 2) were downregulated. EXCC/cisplatin treatment produced more DNA damage than the single treatments, as indicated by γH2AX and 8-hydroxy-2'-deoxyguanosine levels. Moreover, several DNA repair genes for homologous recombination (HR) and non-homologous end joining (NHEJ) were downregulated in EXCC/cisplatin compared to others. The addition of the GSH precursor N-acetylcysteine, which has ROS scavenging activity, attenuated all EXCC/cisplatin-induced changes. Notably, EXCC/cisplatin showed lower antiproliferation, apoptosis, ROS induction, GSH depletion, and γH2AX DNA damage in normal cells than in bladder cancer cells. Therefore, the co-treatment of EXCC/cisplatin reduces the proliferation of bladder cancer cells via oxidative stress-mediated mechanisms with normal cell safety.

La sobreexpresión de poli (ADP-ribosa) polimerasa se correlaciona con el desarrollo de necrosis tubular aguda y con la función precoz del trasplante renal / Poly (ADP-ribose) polimerase overexpression is correlationship with develop of acute tubular necrosis and early function of renal allograft

Poli (ADP-Ribosa) polimerasa (PARP-1) cataliza la ADP ribosilación de proteínas usando NAD(+) como sustrato. La activación de PARP-1 conduce a la depleción intracelular de NAD(+). El daño por isquemia-reperfusión (IR) induce una activación excesiva de PARP-1 y la muerte celular por consumo masivo de ATP. Nuestra hipótesis de trabajo es que la excesiva expresión tubular de PARP-1 en riñones humanos trasplantados es una de las causas directas de la inducción de necrosis tubular aguda (NTA) y contribuye al retraso de la función renal del injerto. Material y Métodos: Estudiamos 193 biopsias de trasplante renal (95 preimplante –biopsia de donante– y 98 postrasplante) incluidas en parafina con diferentes grados de NTA y 65 biopsias renales de donante sin NTA. La NTA se estratificó en cuatro grados: ausente (0); leve (1) [50%]. La expresión nuclear de PARP-1 fue evaluada mediante inmunohistoquímica con el kit de polimeros conjugado con peroxidasa MasVision y el anticuerpo anti- PARP-1 (clón PARP01) y valorada semicuantitativamente de 0 a 3. Resultados: La expresión nuclear de PARP-1 antecedió a los cambios morfológicos sugerentes de NTA. Principalmente la inmunotinción se localizó en los núcleos de células tubulares, cuando fue intensa la lesión también apareció en glomérulos (epitelio de la cápsula de Bowman y células endoteliales de capilares glomerulares). La inmunotición fue observable hasta fases finales de la necrosis tubular. La totalidad de las 95 biopsias renales pre-trasplante con NTA grado 1 (86%) o grado 2 (14%) mostraron expresión nuclear de PARP-1 en túbulos. Las 98 biopsias postrasplante con NTA mostraron expresión más intensa de PARP-1 [grado 2 (45%), grado 3 (25%)]. El grado de NTA se correlacionó significantivamente con la expresión de PARP- 1(r=0,565, p=0,0001, test de Pearson), con una expresión media 2,74±0,45 en los casos de NTA severa frente a 1,94±0,74 en los casos de NTA leve y 0,29±0,45 en los casos sin NTA (p=0,0001, test ANOVA de una vía). En conclusión, PARP-1 está vinculado a la inducción de NTA y desempeña un papel importante en el comportamiento de la función precoz del injerto renal ya que está correlacionada significativamente con el tiempo en recuperar la diuresis eficaz (r=0,578, p=0,0001, test de Pearson) y con los niveles séricos de creatinina en el momento de la biopsia (r=0,649), y a los 3 meses (r=0,363, p=0,0001, test de Pearson) pero no a los 6 y 12 meses postrasplante

Poly (ADP-Ribose) Polymerase (PARP-1) catalyzes ADP-ribosylation of proteins using NAD(+) as substrate. Its overactivation leads to massive NAD+ consumption and ATP depletion. The ischemia/reperfusion injury (IR) induces PARP-1 overactivation and leads to cellular necrosis by massive ATP consumption. Our working hypothesis was that massive PARP-1 tubular expression in allograft human kidneys are a direct cause of acute tubular necrosis (ATN) and contribute to delay in early recovery of renal function (RRF) of the transplanted organ. Material and Methods:A total of 193 paraffin embedded renal allograft biopsies (95 pre-implant –donor biopsies– and 98 post-implant) with several ATN degrees, and 65 control renal biopsies from donors without ATN were studied. ATN degree was classified as: Absence (0); mild (1) [50%]. Nuclear expression of PARP-1 in tubular cells was evaluated by immunohistochemistry using polymer-conjugate MasVision kit and the monoclonal antibody anti-PARP-1 (clone PAR01). It was semiquantitatively determined, and scored from 0 to 3. Results: The nuclear PARP-1 preceded the morphological features of ATN. Immunostaining was located mainly in tubular cells nuclei, in cases of intense injury also was observed in glomeruli (capillary endothelial cells and epithelial cells of Bowman’s capsule). Immunostaining was observed until advanced ATN condition. All 95 pre-transplant renal biopsies with ATN degree 1 (86%) or degree 2 (14%) showed tubular nuclei PARP-1 expression. The 98 post-transplant biopsies with ATN showed more intense expression of PARP-1 [degree 2 (45%), degree 3 (25%)]. Statistically significant relationship between ATN degree and PARP-1 expression was found (r=0.565, p=0.0001, Pearson test), with a mean expression of 2.74±0.45 in sever ATN cases versus 1.94±0.74 in mild ATN cases, and 0.29±0.45 in non-ATN cases (p=0.0001, one way ANOVA test). In conclusion, PARP-1 are linked to induction of ATN, and plays an important role in early graft renal function. This fact is indicated by the stati! stically significant relation with delay in total RRF (r=0.578, p=0.0001, Pearson test), creatinine serum levels at biopsy time (r=0.649) and at 3 months (r=0.363, p=0.0001, Pearson test), but not at 6 or 12 months post-transplant