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At least 19 recordsLinked to original sources
PubMed1990

Procyclic acidic repetitive protein (PARP) genes located in an unusually small alpha-amanitin-resistant transcription unit: PARP promoter activity assayed by transient DNA transfection of Trypanosoma brucei.

At least one of the procyclic acidic repetitive protein (PARP or procyclin) loci of Trypanosoma brucei is a small (5- to 6-kilobase) polycistronic transcription unit which is transcribed in an alpha-amanitin-resistant manner. Its single promoter, as mapped by run-on transcription analysis and UV inactivation of transcription, is located immediately upstream of the first alpha-PARP gene. Transcription termination occurs in a region approximately 3 kilobases downstream of the beta-PARP gene. The location of the promoter was confirmed by its ability to direct transcription of the bacterial chloramphenicol acetyltransferase gene in insect-form (procyclic) T. brucei. The putative PARP promoter is located in the region between the 3' splice acceptor site (nucleotide position 0) and nucleotide position -196 upstream of the alpha-PARP genes. Regulatory regions influencing the levels of PARP expression may be located further upstream. We conclude that a single promoter, which is located very close to the 3' splice acceptor site of the alpha-PARP genes, directs the transcription of a small, polycistronic, and alpha-amanitin-resistant transcription unit.

Amanitins↗
PubMed2026

Long-Term Outcomes in Patients With Recurrent Ovarian Cancer and Exceptional Response to PARP Inhibitors.

IMPORTANCE: A subset of patients with platinum-sensitive recurrent ovarian cancer (PS-ROC) treated with maintenance poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors have exceptional response. Although licensing recommends continuing PARP inhibitors until progression or unacceptable toxic effects, the optimal duration of PARP inhibitors, and the risks of late progression, myelodysplastic syndrome (MDS), or acute myeloid leukemia (AML) in patients with exceptional response are unknown. OBJECTIVE: To determine the long-term outcomes of patients with PS-ROC who have exceptional response to PARP inhibitors, and to explore genotype-phenotype associations. DESIGN, SETTING, AND PARTICIPANTS: This was an international, multicenter, retrospective cohort study of patients with exceptional response to PARP inhibitors, defined as patients with PS-ROC and progression-free survival (PFS) of 5 years or longer from PARP inhibitor commencement. The study was conducted across 41 sites in 14 countries from January 11, 2023, to November 10, 2025. EXPOSURES: Treatment with PARP inhibitors. MAIN OUTCOMES AND MEASURES: The primary end point was PFS, and secondary end points included overall survival, toxic effects, and dose reductions. RESULTS: A total of 320 patients with exceptional response (mean [SD] age, 56.4 [9.4] years) were included, with a median follow-up of 6.8 years (95% CI, 6.6-7.0 years). The median (IQR) PARP inhibitor duration was 75.0 (64.0-91.0) months. Of patients with exceptional response, 211 (65.9%) received continuous PARP inhibitors, but 109 (34.1%) discontinued: 34 (10.6%) due to physician recommendation, 2 (7.5%) had disease progression beyond 5 years, 22 (6.9%) had toxic effects, 17 (5.3%) for patient preference, and 12 (3.8%) for another reason. The 7.5-year and 10-year PFS rates were 88.8% (95% CI, 84.5%-93.3%) and 78.7% (95% CI, 70.5%-87.9%), respectively. Among the patients, 85 (26.6%) discontinued PARP inhibitors for reasons other than disease progression, with a 10-year PFS of 90.1% (95% CI, 80.6%-100%) vs 72.5% (95% CI, 60.3%-87.2%) for those who continued taking PARP inhibitors. Five patients (1.6%) were diagnosed with late-onset MDS/AML. Patients with exceptional response were enriched for variants in the BRCA1 RING domain and the BRCA2 DNA-binding domain. CONCLUSIONS AND RELEVANCE: In this cohort study, most patients with exceptional response to PARP inhibitors remained progression free, including those who discontinued PARP inhibitors without progression. The risk of late-onset MDS/AML was low. These results can guide counseling on the duration of maintenance PARP inhibitors in patients with exceptional response and suggest that functional cure may be possible in patients with PS-ROC and exceptional response to PARP inhibitors.

Humans↗
PubMed2026

Computational discovery of emodin-based anthraquinones as PARP-1 inhibitors with relevance to ovarian and prostate cancer.

Cancer is a disease characterized by genomic instability and aberrant DNA repair. Poly (ADP-ribose) polymerase-1 (PARP-1) represents a well-established therapeutic target, particularly in ovarian and prostate cancer. However, the currently approved PARP inhibitors face challenges such as resistance, toxicity, and reduced efficacy. The search for alternative scaffolds has therefore become increasingly urgent. In this study, we used an integrated approach combining computer-aided methods to search for potential lead compounds among emodin-based anthraquinone derivatives as PARP-1 inhibitors. Using a PASS-based QSAR approach, drug-likeness prediction, and in silico ADMET assessment, we pre-screened a large set of anthraquinones and identified several potential hits for interaction with PARP-1. These hits were studied using molecular docking with the PARP-1 catalytic domain (PDB ID: 7KK4). The most stable and compact complexes were further explored by 500 ns molecular dynamics (MD) simulations and various dynamic properties (RMSD, RMSF, Rg, SASA, MolSA, hydrogen bonds, PCA, DCCM). The key finding of this study is that several emodin-derived anthraquinones exhibited binding behavior and ADMET profiles comparable to, or better than, the reference PARP-1 inhibitor. Among them, CID-10425624 emerged as the most promising candidate, exhibiting stable binding, reduced conformational fluctuation, compact complex formation, persistent hydrogen-bond interactions, and enhanced dynamic residue correlations within the PARP-1 catalytic domain. These findings suggest that the anthraquinone scaffold can provide a valuable starting point for developing structurally distinct PARP-1 inhibitors. In summary, this study identified several emodin-derived anthraquinones, particularly CID-10425624, as computationally prioritized lead candidates for PARP-1 inhibition, providing a novel anthraquinone-based scaffold for further experimental validation and optimization.

Anthraquinones↗
PubMed2025

Targeting RAD52 overcomes PARP inhibitor resistance in preclinical Brca2-deficient ovarian cancer model.

BRCA-mutated ovarian cancer commonly develops resistance to poly (ADP-ribose) polymerase (PARP) inhibitors. Here, we investigated the DNA repair protein RAD52 as a potential target to overcome resistance. In analysis of The Cancer Genome Atlas datasets and immunohistochemistry of tissue microarrays, elevated RAD52 expression correlated with poor overall survival in patients with high-grade serous ovarian cancers. We tested two PARP inhibitor-resistant Brca2-deficient mouse ovarian cancer models, ID8-OR and HGS2-OR. HGS2-OR cells had higher RAD52 expression than parental lines. Rad52 knockout or knockdown restored PARP inhibitor sensitivity in both models. In syngeneic mice, ID8-OR cells in which Rad52 was knocked out yielded lower tumor burden and longer overall survival than control cells. Rad52 depletion impaired single-strand annealing and homologous recombination and led to accumulation of DNA double-strand breaks after PARP inhibitor treatment. RNA sequencing demonstrated that PARP inhibitor treatment induced Polq expression in Brca2- and Rad52-deficient cells, suggesting a switch to microhomology-mediated end joining. Finally, the RAD52 inhibitor D-I03 synergized with a PARP inhibitor to reduce cell viability and tumor burden and prolong survival. Collectively, our findings establish RAD52 as a promising therapeutic target to overcome PARP inhibitor resistance in BRCA2-mutated ovarian cancer and offer mechanistic insights to inform future clinical strategies.

Journal Article↗
PubMed1992

The promoter for the procyclic acidic repetitive protein (PARP) genes of Trypanosoma brucei shares features with RNA polymerase I promoters.

All eukaryotic protein-coding genes are believed to be transcribed by RNA polymerase (Pol) II. An exception may exist in the protozoan parasite Trypanosoma brucei, in which the genes encoding the variant surface glycoprotein (VSG) and procyclic acidic repetitive protein (PARP) are transcribed by an RNA polymerase that is resistant to the Pol II inhibitor alpha-amanitin. The PARP and VSG genes were proposed to be transcribed by Pol I (C. Shea, M. G.-S. Lee, and L. H. T. Van der Ploeg, Cell 50:603-612, 1987; G. Rudenko, M. G.-S. Lee, and L. H. T. Van der Ploeg, Nucleic Acids Res. 20:303-306, 1992), a suggestion that has been substantiated by the finding that trypanosomes can transcribe protein-coding genes by Pol I (G. Rudenko, H.-M. Chung, V. P. Pham, and L. H. T. Van der Ploeg, EMBO J. 10:3387-3397, 1991). We analyzed the sequence elements of the PARP promoter by linker scanning mutagenesis and compared the PARP promoter with Pol I, Pol II, and Pol III promoters. The PARP promoter appeared to be of limited complexity and contained at least two critical regions. The first was located adjacent to the transcription initiation site (nucleotides [nt] -69 to +12) and contained three discrete domains in which linker scanning mutants affected the transcriptional efficiency: at nt -69 to -56, -37 to -11, and -11 to +12. The second region was located between nt -140 and -131, and a third region may be located between nt -228 and -205. The nucleotide sequences of these elements, and their relative positioning with respect to the transcription initiation site did not resemble those of either Pol II or Pol III promoter elements, but rather reflected the organization of Pol I promoters in (i) similarity in the positioning of essential domains in the PARP promoter and Pol I promoter, (ii) strong sequence homology between the PARP core promoter element (nt -37 to -11) and identically positioned nucleotide sequences in the trypanosome rRNA and VSG gene promoters, and (iii) moderate effects on promoter activity of mutations around the transcription initiation site.

Base Sequence↗
PubMed1990

Isolation and primary structure of PARP, a 24-kDa proline- and arginine-rich protein from bovine cartilage closely related to the NH2-terminal domain in collagen alpha 1 (XI).

A protein rich in proline and arginine (proline/arginine-rich protein (PARP] has been isolated from dissociative extracts of bovine nasal and articular cartilage, and its primary structure has been determined. The protein has 218 amino acids, giving a calculated protein Mr of 24,075. In nasal cartilage, this protein is in molar concentrations equivalent to 1/20-1/10 that of the link protein of cartilage proteoglycan aggregates. PARP has also been isolated from bovine articular cartilage, bovine fetal epiphysis, and nonossified human tarsal bones. PARP is similar to various collagen NH2-terminal domains. It is 49% identical to the NH2-terminal end of collagen alpha 1 (XI), 17% identical to the NC4 domain of collagen alpha 1 (IX), and 14% identical to the NC3 domain of collagen alpha 1 (XII). Four cysteines are conserved between type XI collagen and PARP, and these form two disulfide bonds. Two of the cysteines are also conserved between PARP and collagens IX and XII. The homology between the collagens and PARP makes it possible to speculate on the likely disulfide bond pattern in the collagen NH2-terminal domains. It is probable that PARP is a collagen fragment removed during processing in a manner analogous to chondrocalcin (the C-terminal propeptide of type II collagen).

Amino Acid Sequence↗
PubMed2025

Repression of PRMT activities sensitize homologous recombination-proficient ovarian and breast cancer cells to PARP inhibitor treatment.

Therapeutic epigenetic modulation is currently being evaluated in the clinic to sensitize homologous recombination (HR)-proficient tumors to PARP inhibitors. To broaden its clinical applicability and identify more effective combination strategies, we conducted a drug screen combining PARP inhibitors with 74 well-characterized epigenetic modulators targeting five major classes of epigenetic enzymes. Notably, both type I PRMT inhibitors and PRMT5 inhibitors scored highly in combination efficacy and clinical prioritization. PRMT inhibition significantly enhanced PARP inhibitor-induced DNA damage in HR-proficient ovarian and breast cancer cells. Mechanistically, PRMT suppression downregulates DNA damage repair genes and BRCAness-associated pathways, while also modulating intrinsic innate immune responses within cancer cells. Integrative analysis of large-scale genomic and functional datasets from TCGA and DepMap further supports PRMT1, PRMT4, and PRMT5 as promising therapeutic targets in oncology. Importantly, dual inhibition of PRMT1 and PRMT5 synergistically sensitizes tumors to PARP inhibitors. Collectively, our findings provide strong rationale for the clinical development of PRMT and PARP inhibitor combinations in HR-proficient ovarian and breast cancers.

Journal Article↗
PubMed2024

DNA damage-induced EMT controlled by the PARP-dependent chromatin remodeler ALC1 promotes DNA repair efficiency through RAD51 in tumor cells.

Epithelial-to-mesenchymal transition (EMT) allows cancer cells to metastasize while acquiring resistance to apoptosis and chemotherapeutic agents with significant implications for patients' prognosis and survival. Despite its clinical relevance, the mechanisms initiating EMT during cancer progression remain poorly understood. We demonstrate that DNA damage triggers EMT and that activation of poly (ADP-ribose) polymerase (PARP) and the PARP-dependent chromatin remodeler ALC1 (CHD1L) was required for this response. Our results suggest that this activation directly facilitates access to the chromatin of EMT transcriptional factors (TFs) which then initiate cell reprogramming. We also show that EMT-TFs bind to the RAD51 promoter to stimulate its expression and to promote DNA repair by homologous recombination. Importantly, a clinically relevant PARP inhibitor reversed or prevented EMT in response to DNA damage while resensitizing tumor cells to other genotoxic agents. Overall, our observations shed light on the intricate relationship between EMT, DNA damage response, and PARP inhibitors, providing potential insights for in cancer therapeutics.

Humans↗
PubMed2026

The transposable element-PARP axis underpins synthetic lethality and immunogenic vulnerability in blood cancer.

Transposable elements (TEs) are emerging regulators of hematopoiesis and leukemia, creating vulnerabilities exploitable for therapy. Recent evidence shows that TE reactivation induces innate immune signaling, DNA damage responses, and dependence on poly(ADP-ribose) polymerase (PARP)-mediated protection, enabling synthetic lethality with PARP inhibition even in homologous recombination-proficient leukemias with epigenetic gene mutations. In this article, we highlight the biology underpinning this novel TE-PARP axis, its therapeutic implications, and strategies to expand PARP inhibition beyond HR-deficient cancers through rational combinations with immunotherapy and refined patient stratification.

Humans↗
PubMed2025

Role of GDH and PARP inhibitors as novel treatments for SDHB-deficient PPGLs.

SDHB, one of the four genes encoding the subunits of the Krebs cycle enzyme succinate dehydrogenase (SDH), acts as a tumor suppressor in several human cancers, including pheochromocytomas/paragangliomas. Mutations in SDHB lead to a reduction or complete loss of enzymatic activity, linking SDHB to paraganglioma malignancy. Given the difficulty in curing metastatic paragangliomas and the limited value of surgery, new treatments are needed. Glutamine dehydrogenase 1 (GDH1), a key regulator of glutathione metabolism, and poly (ADP-ribose) polymerase (PARP), essential for repairing single- or double-stranded DNA breaks, are crucial in cancer initiation and progression. We treated the human pheochromocytoma cell line (hPheo1) with knocked-down SDHB using radiation, the GDH inhibitor 'R162', and the PARP inhibitor 'olaparib'. Combining R162 with radiation enhances anticancer effectiveness, reduces cell proliferation, and causes G2/M phase arrest in the wild-type and KD-SDHB hPheo1 cell line. KD-SDHB hPheo1 cells treated with olaparib alone were more resistant than wild-type cells but were more sensitive in combination with radiation, activated repair mechanisms, and halted cell cycle progression at the G2/M phase. These results suggest that enhancing radiation-induced DNA damage could be a potential treatment strategy for metastatic pheochromocytomas/paragangliomas. Inhibiting GDH1 and PARP activities, with radiation, may represent promising strategies for the treatment of SDHB-deficient pheochromocytoma/paraganglioma; however, their effects do not appear to be specific to SDHB-deficient cells and require further validation.

Humans↗
PubMed1991

Anatomy of the parp gene promoter of Trypanosoma brucei.

While growing in the tsetse fly, Trypanosoma brucei expresses a major surface glycoprotein, the procyclic acidic repetitive protein (PARP). The parp genes are transcribed by an alpha-amanitin-resistant RNA polymerase. We have determined the sequence requirements for parp promoter activity. Studies of RNA produced from input DNA in transiently transfected trypanosomes indicate that the RNA is correctly processed by trans-splicing and polyadenylation. Deletion analyses show that 330 bp are sufficient for full promoter and splicing activity and that the promoter structure is complex, involving at least three elements whose mutual spacing is important. Mutagenesis pin-pointed two sequences vital for promoter activity; neither bears any resemblance to known prokaryotic or eukaryotic promoter elements.

Animals↗
PubMed2026

Bipolar Androgen Therapy as a Potential Mechanistic Bridge to Enhance PARP Inhibitor Efficacy in Prostate Cancer.

Prostate cancer remains a leading cause of cancer-related mortality, largely driven by progression to metastatic castration-resistant prostate cancer (mCRPC). Although poly(ADP-ribose) polymerase inhibitors (PARPis) have improved outcomes in patients with homologous recombination repair (HRR) alterations, particularly in BRCA2-mutated disease, their clinical benefit is limited by restricted patient selection, modest efficacy in non-BRCA HRR alterations, and the frequent emergence of resistance. These limitations highlight an unmet need for strategies that can both expand the therapeutic population and overcome PARPi resistance. Bipolar androgen therapy (BAT), which alternates between supraphysiological and near-castrate androgen exposure, has emerged as a paradoxical yet clinically active approach in mCRPC. Unlike conventional androgen deprivation strategies, preclinical evidence suggests that BAT induces acute androgen receptor-mediated DNA damage while simultaneously suppressing HRR gene expression. This dual effect may generate a transcription-coupled homologous recombination-deficient state that is independent of canonical baseline genomic HRR alterations, thereby potentially sensitizing tumors to PARP inhibition. Current clinical trials of BAT combined with PARP inhibitors suggest activity in both HRR-deficient and HRR-proficient disease. Collectively, these findings suggest a preliminary, hypothesis-generating conceptual framework in which BAT may expand the therapeutic scope of PARPis beyond genomically defined HRR-mutated tumors and may help counteract mechanisms of PARPi resistance in mCRPC.

PARP inhibitor↗
PubMed1991

Requirement of a polypyrimidine tract for trans-splicing in trypanosomes: discriminating the PARP promoter from the immediately adjacent 3' splice acceptor site.

We studied sequence requirements for trans-splicing at the 3' splice acceptor site of a procyclic acidic repetitive protein (PARP) coding gene in trypanosomes. In transient CAT transfection assays with linker scanning (LS) mutants in a PARP promoter--3' splice acceptor site--CAT construct, minor differences in the sequence composition of the polypyrimidine tract (nt -36 to -5 with respect to the 3' splice acceptor site) severely affected the CAT activity. Analysis of steady-state CAT RNA in stably transformed trypanosomes revealed that the LS mutations had indeed affected the pre-mRNA splicing efficiency. The data indicate that mini-exon addition is not required simply for maturation of polycistronic pre-mRNA but is also essential for the generation of functional mRNA from monocistronic genes, since unspliced monocistronic pre-mRNA did not accumulate or allow synthesis of CAT. We postulate that mini-exon addition at polycistronically transcribed genes, which can have drastically different polypyrimidine tracts at each of their 3' splice acceptor sites, can occur with different efficiencies for each gene of the array thus affecting mRNA abundance.

Animals↗
PubMed1992

The PARP and VSG genes of Trypanosoma brucei do not resemble RNA polymerase II transcription units in sensitivity to Sarkosyl in nuclear run-on assays.

Addition of the ionic detergent N-lauroylsarcosine (Sarkosyl) affects the efficiency of transcription of genes of the protozoan Trypanosoma brucei in nuclear run-on assays. Transcription of the PARP (procyclin or procyclic acidic repetitive protein), variant cell surface glycoprotein (VSG) and ribosomal RNA (rRNA) genes was resistant or increased after addition of Sarkosyl. In contrast, the transcription of seven protein coding house keeping genes and the mini-exon donor RNA (medRNA) genes was completely abolished by the addition of Sarkosyl, while the transcription of the 5S rRNA genes showed an intermediate sensitivity. We conclude that Sarkosyl can be used to discriminate between the different types of trypanosome transcription units. The PARP and VSG protein coding genes had previously been postulated to be transcribed by an RNA polymerase I-like enzyme on the basis of their resistance to the RNA polymerase II inhibitor alpha-amanitin. This model is now supported by their resistance to the addition of Sarkosyl.

Animals↗
PubMed2024

Induced degradation of lineage-specific oncoproteins drives the therapeutic vulnerability of small cell lung cancer to PARP inhibitors.

Although BRCA1/2 mutations are not commonly found in small cell lung cancer (SCLC), a substantial fraction of SCLC shows clinically relevant response to PARP inhibitors (PARPis). However, the underlying mechanism(s) of PARPi sensitivity in SCLC is poorly understood. We performed quantitative proteomic analyses and identified proteomic changes that signify PARPi responses in SCLC cells. We found that the vulnerability of SCLC to PARPi could be explained by the degradation of lineage-specific oncoproteins (e.g., ASCL1). PARPi-induced activation of the E3 ligase HUWE1 mediated the ubiquitin-proteasome system (UPS)-dependent ASCL1 degradation. Although PARPi induced a general DNA damage response in SCLC cells, this signal generated a cell-specific response in ASCL1 degradation, leading to the identification of HUWE1 expression as a predictive biomarker for PARPi. Combining PARPi with agents targeting these pathways markedly improved therapeutic response in SCLC. The degradation of lineage-specific oncoproteins therefore represents a previously unidentified mechanism for PARPi efficacy in SCLC.

Humans↗
PubMed2026

Patient-derived organoids predict responses to chemotherapy and PARP inhibitors in advanced ovarian cancer.

BACKGROUND: While tumor organoids hold promise for personalized medicine, clinical validation of epithelial ovarian cancer (EOC) organoids as predictors of therapeutic efficacy-particularly for PARP inhibitors (PARPi)-remains unestablished. METHODS: Patient-derived organoids (PDOs) were established from treatment-naive EOC specimens and characterized by H&E staining, immunohistochemistry, and whole-exome sequencing. Drug sensitivity testing (DST) was performed using carboplatin, paclitaxel, and PARPi (olaparib and niraparib). Clinical homologous recombination deficiency (HRD) status was assessed by tumor sequencing. Organoid responses were prospectively compared to patient outcomes after first-line chemotherapy (carboplatin/paclitaxel) and PARPi maintenance. RESULTS: PDOs were successfully established from 21 of 30 patients (70%) across multiple EOC subtypes and preserved the histopathological features and genomic landscapes of their corresponding primary tumors. Organoid-based DST accurately predicted responses to first-line carboplatin/paclitaxel, with a sensitivity of 100% (95% CI 62.88-100%), specificity of 66.67% (95% CI 12.53-98.23%), accuracy of 91.67% (95% CI 61.52-99.79%), AUC of 0.95 (95% CI 0.85-1.00), and Cohen's kappa of 0.75 (95% CI 0.30-1.00). In evaluating PARPi response, organoids revealed discrepancies between genomic HRD status and actual drug responses. One HRD-positive PDO was PARPi-resistant, consistent with patient non-response, while two HRR-proficient PDOs showed PARPi sensitivity and corresponding clinical benefit. CONCLUSIONS: EOC-derived PDOs provide a robust platform for predicting chemotherapy response and offer added value in assessing PARPi efficacy beyond genomic profiling. Combination of organoid-based testing with genomic analysis may improve precision treatment strategies in EOC.

Humans↗
PubMed2026

CRISPR screen identifies autophagy inhibition (GNS561) as a PARP inhibitor (AZD5305) combination strategy in small cell lung cancer.

BACKGROUND: Small cell lung cancer (SCLC) is a deadly cancer with few treatment options and poor prognosis, creating a dire need for improving therapies. Poly (ADP-ribose) polymerase inhibitors (PARPi) have been tested as a treatment strategy, but patient response varies. We aimed to identify novel approaches to sensitize SCLC to PARPi through a genome-wide CRISPR dropout screen. METHODS: Genome-wide CRISPR dropout screening was conducted in two SCLC cell lines using the PARPi, olaparib, as the selection pressure. Stable shRNA-mediated knockdown cell lines were validated by Western blotting and tested for olaparib sensitivity by assaying for cell viability. Synergy between PARPi and autophagy inhibition was tested by treating SCLC cell lines and analyzing cell viability using SynergyFinder+. The therapeutic strategy combining AZD5305 (PARPi) and GNS561 (novel autophagy inhibitor) was tested in cell line-derived xenograft mouse models. RESULTS: CRISPR screening identified the loss of mTOR negative regulators as a mechanism of PARPi sensitivity in SCLC, and knockdown of TSC1 and TSC2 sensitized SCLC cell lines to olaparib. Therapeutic strategies combining PARPi and autophagy inhibition demonstrated synergy in SCLC cell lines, and combination therapy with AZD5305 and GNS561 was effective in cell line-derived xenograft mouse models. CONCLUSIONS: Autophagy inhibition downstream of the mTOR pathway is a mechanism of PARPi sensitivity in SCLC. This suggests that a therapeutic combination of autophagy inhibition and PARPi is a promising treatment strategy in SCLC, paving the way for the adoption of novel treatments in this disease context.

Autophagy↗
PubMed1991

Inhibition of protein synthesis results in super-induction of procyclin (PARP) RNA levels.

Procyclin is an abundant surface antigen found exclusively on the procyclic forms of African trypanosomes. We are interested in the induction of procyclin gene expression during differentiation from bloodstream forms. We find that increased levels of procyclin RNA are evident as early as 15 min after triggering differentiation. The increase in procyclin RNA levels requires the temperature shift from 37 degrees C to 27 degrees C and is aided by addition of the tricarboxylic acid cycle intermediate cis-aconitate. Maximal induction is observed with a combination of three triggers of differentiation: citrate, cis-aconitate and the temperature shift. Protein synthesis does not appear to be required for induction of procyclin RNA during differentiation. In fact, addition of protein synthesis inhibitors results in super-induction of procyclin RNA levels, even under conditions where no induction is normally observed (i.e., at 37 degrees C in the absence of citrate and cis-aconitate). This super-induction was observed with four different protein synthesis inhibitors that affect different stages of translation. Thus, the accumulation of procyclin transcripts may be under the control of a negative regulator whose effective levels are reduced during differentiation from bloodstream to procyclic forms.

Aconitic Acid↗