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J. Burgess
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MA 03 - Chemotherapy (ID 651)
- Event: WCLC 2017
- Type: Mini Oral
- Track: Advanced NSCLC
- Presentations: 1
- Moderators:Jin-Hyoung Kang, W. Su
- Coordinates: 10/16/2017, 11:00 - 12:30, Room 502
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MA 03.11 - Targeting CDCA3 Enhances Sensitivity to Platinum-Based Chemotherapy in Non-Small Cell Lung Cancer (ID 9607)
11:00 - 12:30 | Author(s): J. Burgess
- Abstract
- Presentation
Background:
Lung cancer is the leading cause of cancer-related mortality worldwide with a 5 year survival rate of 15%. Non-small cell lung cancer (NSCLC) is the most commonly diagnosed form of lung cancer. Cisplatin-based regimens are currently the most effective chemotherapy for NSCLC, however, chemoresistance poses a major therapeutic problem. New and reliable strategies are required to avoid drug resistance in NSCLC. Cell division cycle associated 3 (CDCA3) is a key regulator of the cell cycle. CDCA3 modulates this process by enabling cell entry into mitosis through degradation of the mitosis-inhibitory factor WEE1. Herein, we describe CDCA3 as a novel prognostic target to delay or prevent cisplatin resistance in NSCLC.
Method:
CDCA3 expression was investigated using bioinformatic analysis, tissue microarray immunohistochemistry and western blot analysis of matched NSCLC tumour and normal tissue. CDCA3 function in NSCLC was determined using several in vitro assays by siRNA depleting CDCA3 in a panel of three immortalized bronchial epithelial cell lines (HBEC) and seven NSCLC cell lines. To determine strategies to suppress CDCA3 activity the phosphorylation status of CDCA3 was assessed using mass spectrometry analysis. Kinases that phosphorylate CDCA3 were identified using a siRNA screen and high content immunofluorescence and microscopy approaches.
Result:
We have previously shown that CDCA3 transcripts and protein levels are elevated in resected NSCLC patient tissue, high mRNA levels being associated with poor survival. CDCA3 depletion markedly impairs proliferation in seven NSCLC cell lines by inducing a G2 cell cycle arrest. Silencing of CDCA3 also greatly sensitises NSCLC cell lines to cisplatin. Consistently, NSCLC patients with elevated CDCA3 levels and treated with cisplatin have a poorer outcome than patients with reduced CDCA3 levels. To aid patient response to cisplatin, we have been looking at strategies to suppress CDCA3 expression in tumour cells. Accordingly, in response to cisplatin, CDCA3 is phosphorylated (S[222]) via casein kinase 2 (CK2) which prevents CDCA3 degradation in NSCLC cells. Moreover, the CK2 inhibitor CX-4945 reduces CDCA3 levels in cisplatin treated cells. CX-4945 increased cisplatin-induced cell death in control cells. The efficacy was further enhanced in CDCA3 depleted NSCLC cells.
Conclusion:
Our data highlight CDCA3 as a novel factor in the pathogenesis of NSCLC. We propose that preventing cisplatin-induced CDCA3 phosphorylation by targeting CK2 is a worthwhile and novel strategy in treating NSCLC and may ultimately benefit patient outcome by preventing cisplatin resistance.
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P1.02 - Biology/Pathology (ID 614)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Biology/Pathology
- Presentations: 3
- Moderators:
- Coordinates: 10/16/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P1.02-010 - Novel Role of hSSB2 in the Base Excision Repair Pathway (BER) (ID 9579)
09:30 - 16:00 | Author(s): J. Burgess
- Abstract
Background:
The base excision repair (BER) pathway is responsible for removing damaged or incorrectly incorporated uracil bases in the genome. Mismatched bases that persist in the genome and remain unrepaired may result in either lethal mutations or cytotoxic DNA double strand breaks. Previous studies have determined that hSSB1 is critical for the detection, signaling and repair of cytotoxic double strand DNA breaks and oxidized DNA lesions within the genome. The role of hSSB2 is, however, less clear. In this study, we have identified that the single stranded DNA binding proteins, hSSB1 and 2, are involved in the detection and removal of uracils within the genome and function as part of the BER pathway.
Method:
We identified a novel role for hSSB1 and hSSB2 in BER. EMSA and incision biochemical assays were used to determine the ability of hSSB1/2 to bind uracil containing mismatches. Incision assays were used to determine the effect hSSB2 and hSSB1 have on UNG2 activity. Two cytotoxic drugs (5-fluorouracil and pemetrexed), which induce uracil misincorporation in the genome, were used to determine the cell sensitivity in control and hSSB1/2-depleted cells using a live and dead cell assay. Immunoprecipitation, immunofluorescence and Protein-Protein interactions were carried out to determine whether hSSB2 and hSSB1 interacts with key regulatory proteins of the BER pathway.
Result:
This study demonstrates that hSSB1 and hSSB2 proteins can recognize and bind to double stranded DNA substrates containing a uracil mismatch. Interestingly, we have identified that hSSB1 and hSSB2 have a differential preference for uracil mismatches, with hSSB1 preferentially binding UA and hSSB2 UG mismatches. Furthermore, hSSB2 induces the incision activity of UNG2 by approximately two fold for a U:G mismatch but not a U:A mismatch. A549 lung adenocarcinoma cells depleted of both hSSB1 and hSSB2 are hypersensitive to 5-fluorouracil and pemetrexed. Loss of either hSSB1 or hSSB2 alone by siRNA results in a compensatory upregulation of hSSB2 or hSSB1 respectively, suggesting over-lapping functionality and substrate specificity.
Conclusion:
This study highlights the importance of hSSB2 and hSSB1 in the removal of uracil from the genome. Currently, pemetrexed and fluorouracil based agents are in use for treating lung cancer. This study raises the possibility that hSSB2 and hSSB1 may be biological indicators of response to fluorouracil and pemetrexed. Further, it may be possible to develop future hSSB2/hSSB1 inhibitors that could enhance the activity of these agents in the treatment of lung cancer.
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P1.02-071a - Targeting Human Single Stranded DNA Binding Protein (hSSB) 1, a Novel Prognostic Factor, in Non-Small Cell Lung Cancer (ID 9210)
09:30 - 16:00 | Author(s): J. Burgess
- Abstract
Background:
Lung cancer is the leading cause of cancer death worldwide. The hallmark of all malignant disease is genomic instability leading to tissue invasion, metastasis and resistance to chemotherapy, notably cisplatin. hSSB1 is a guardian of the genome with a key role in the detection and repair of DNA double-strand breaks, replication fork arrest and oxidative stress damage. Recently we have shown that hSSB1 is directly phosphorylated by DNA-PK at serine residue 134 in response to replication stress to promote cellular survival. We hypothesized that hSSB1 may play a role in the pathogenesis of non-small cell lung cancer (NSCLC) and in the mechanism of resistance to cisplatin based chemotherapy observed for (NSCLC). Therefore we evaluated the role of hSSB1 as a prognostic factor and as a potential new target for therapy.
Method:
We analyzed the prognostic significance of hSSB1 mRNA expression from public on line databases and through assessment of protein expression in an NSCLC tissue macro-array (TMA) using immunohistochemistry. hSSB1 mRNA levels were analyzed in matched normal:tumour adenocarcinoma and squamous cell tumour samples, and in a platinum sensitive vs resistant cells. We also explored the impact of hSSB1 expression on NSCLC cell lines sensitivity to cisplatin (measured by cell proliferation) by over-expressing a Flag tagged hSSB1 or depleting hSSB1 with specific small interfering (si)RNA.
Result:
hSSB1 expression was associated with poor prognosis for lung cancer, high levels of mRNA and protein expression correlating with a worse overall survival. hSSB1 mRNA levels were prognostic in adenocarcinomas only. hSSB1 mRNA was also significantly increased in both adenocarcinoma and squamous cell carcinoma compared to matched normal tissue. Furthermore, we observed that hSSB1 was upregulated in H460 cisplatin resistant cells as compared to the parental line. Knockdown of hSSB1 in H460 cells was associated with a significant increase in sensitivity to cisplatin.
Conclusion:
Our results establish hSSB1 as a prognostic factor in non-small cell lung cancer. Moreover, targeting hSSB1 may prove an effective method of reversing platinum resistance. Evaluation of the potential role of DNA-PK inhibition in inhibiting hSSB1 activation and reversing cisplatin and radiotherapy resistance in tumours with high levels of hSSB1 expression is currently ongoing.
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P1.02-071b - SASH1 Is a Prognostic Indicator and Future Target in NSCLC (ID 9591)
09:30 - 16:00 | Author(s): J. Burgess
- Abstract
Background:
Lung cancer is the most commonly diagnosed cancer in the world and the fifth most common in Australia, where it is responsible for almost one in five cancer deaths. SASH1 (SAM and SH3 domain-containing protein 1) is a tumor suppressor functioning to control of apoptosis and cellular proliferation. Previously SASH1 has been shown to be down-regulated in approximately 90% of lung cancers, however little is known about the role of SASH1 in the pathogenesis of the disease. Cytotoxic platinum based chemotherapy two-drug regimens remain a cornerstone NSCLC patient care, however, resistance to these agents is almost inevitable. The re-sensitisation of these cancer cells to chemotherapeutics is a key to improving patient survival. We hypothesised that modulation of SASH1 expression may alter cisplatin sensitivity.
Method:
A panel of lung cancer cell lines depleted of SASH1 (siRNA) or overexpressing SASH1 were analysed for protein levels via immunoblotting, cell proliferation, and survival/death assays. Treatment of lung cancer cells with the SASH1 protein stabilising compound chloropyramine (0-50 μM) and/or cisplatin (0-10 μM) was performed followed by immunoblotting for SASH1, cell proliferation, and survival/death assays. SASH1 IHC staining of adenocarcinoma and Squamous cell carcinomas was correlated with patient survival.
Result:
We demonstrated that SASH1 depletion results in a significant increase in cellular proliferation of NSCLC cancer cells. The depletion of SASH1 within lung cancer cell lines was associated with a significant increase in cisplatin resistance. Transfection of SASH1 into NSCLC cell lines induced cell death. The treatment of cells with the SASH1 protein stabilising compound chloropyramine increased SASH1 levels, reduced proliferation and induced apoptosis. Furthermore, chloropyramine increased cisplatin sensitivity. The relationship between SASH1 protein expression with overall survival was accessed in a NSCLC TMA panel. This showed that high SASH1 protein levels were associated with a poor prognosis in adenocarcinomas but were non-prognostic in squamous cell disease. Interestingly high SASH1 mRNA levels were associated with a favourable prognosis in adenocarcinoma but were not prognostic in squamous cell cancer. In a panel of cancer cell lines we observed no correlation between mRNA and protein levels that may explain this discrepancy.
Conclusion:
Agents that upregulate SASH1, or SASH1 gene therapy, are potential novel approaches to the management of NSCLC. Further preclinical and clinical studies of chloropyramine in combination with chemotherapy are justified in NSCLC.
