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E. Bolderson
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P1.02 - Biology/Pathology (ID 614)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Biology/Pathology
- Presentations: 2
- Moderators:
- Coordinates: 10/16/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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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 - 09:30 | Author(s): E. Bolderson
- 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 - 09:30 | Author(s): E. Bolderson
- 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.
