Kevin M. Kremer

PARP1 inhibition prevents ribosome biogenesis and decreases protein translation. Treatment with niraparib significantly decreases rRNA subunit (18S) production in endometrial (A) and ovarian (B) cancer cells as assayed by qPCR. Each bar represents the mean + SEM; n = 3. Bars marked with asterisks are significantly different; Student t test; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001. Puromycin incorporation is diminished with niraparib treatment in endometrial (C) and ovarian (D) cancer cells as assayed by Western blotting. E and F, Quantification of puromycin incorporation assay from C and D, respectively. Each bar represents the mean + SEM; n = 3. Bars marked with asterisks are significantly different; Student t test; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.

PARP1 inhibition prevents ribosome biogenesis by inhibiting rRNA subunit production

PARP1 inhibition prevents ribosome biogenesis by inhibiting rRNA subunit production

DDX21 nucleolar localization associates with PARP1 expression and decreased survival outcomes. A and B, Representative immunohistochemical staining of PARP1 and DDX21 from endometrial (A) and ovarian (B) cancer commercial tissue microarrays (left) and box plots showing quantification of nucleolar DDX21 intensity in low versus high PARP1 endometrial (A) and ovarian (B) cancer samples (right). Student t test; ****, P < 0.0001. B, Representative IHC images from advanced stage endometrioid endometrial cancer patient samples showing low versus high nucleolar DDX21 staining by IHC. Kaplan–Meier curves showing high nucleolar localization of DDX21 is significantly associated with decreased OS (P-value = 0.0155; D) and PFS (P-value = 0.0092; E) in patients with advanced stage endometrioid endometrial cancer. Total n = 39 (number of patients with low DDX21 nucleolar staining = 14; number of patients with high DDX21 nucleolar staining = 25). log-rank (Mantel–Cox) test; *, P < 0.05; **, P < 0.01.

Niraparib inhibits ADPRylation and disrupts the nucleolar localization of DDX21 in endometrial and ovarian cancer cells. Inhibition of PARP1 catalytic activity in endometrial cancer cell lines (Ishikawa, HEC-1-A, KLE; A) and ovarian cancer cell lines (OVCAR3, OVCAR4, HCC5012; B) by niraparib promotes the redistribution of DDX21 from the nucleolus to the nucleoplasm but does not affect the nucleolar localization of NOP58 as assayed by immunofluorescent staining. C, Quantification of the results from experiments shown in A and B showing the proportion of cells that have disrupted nucleoplasmic localization of DDX21. Each bar represents the mean + SEM; n = 3 (endometrial), n = 6 (ovarian). Bars marked with asterisks are significantly different; Student t test; *, P < 0.05; **, P < 0.01; ***, P < 0.001. D, ADPRylation (PAR) is inhibited in endometrial and ovarian cancer cells treated with niraparib. PARP1 and DDX21 protein expression levels are not affected by niraparib treatment as assayed by Western blotting. E, Quantification of PAR levels from experiments shown in D for endometrial and ovarian cancer cell lines with and without niraparib treatment. Each bar represents the mean + SEM; n = 3. Bars marked with asterisks are significantly different; Student t test; *, P < 0.05; **, P < 0.01.

Niraparib decreases cell growth in endometrial and ovarian cancer cell lines

Endometrial and ovarian cancer cell lines are HR-proficient

Demographic data of 39 advanced stage endometrioid endometrial cancer patients

Demographic data of 39 advanced stage endometrioid endometrial cancer patients

PARP1 inhibition prevents ribosome biogenesis and decreases protein translation. Treatment with niraparib significantly decreases rRNA subunit (18S) production in endometrial (A) and ovarian (B) cancer cells as assayed by qPCR. Each bar represents the mean + SEM; n = 3. Bars marked with asterisks are significantly different; Student t test; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001. Puromycin incorporation is diminished with niraparib treatment in endometrial (C) and ovarian (D) cancer cells as assayed by Western blotting. E and F, Quantification of puromycin incorporation assay from C and D, respectively. Each bar represents the mean + SEM; n = 3. Bars marked with asterisks are significantly different; Student t test; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.