10.4225/03/584a011c7a609
Marini, Kieren David
Kieren David
Marini
Mechanisms of Platinum Chemoresistance in Lung Cancer
Monash University
2019
Platinum
1959.1/1240643
monash:165934
Open access and full embargo
thesis(doctorate)
ethesis-20160125-161947
Chemoresistance
2015
Lung Cancer
2019-08-22 01:16:56
Thesis
https://bridges.monash.edu/articles/thesis/Mechanisms_of_Platinum_Chemoresistance_in_Lung_Cancer/4299338
Lung cancer is the leading cause of cancer-related death. Although platinum-based
chemotherapy is the standard of care for most cases of advanced lung cancer,
resistance limits its effectiveness. Initial treatments with platinum chemotherapies are
effective in small cell lung cancer (SCLC); often resulting in a complete response
with resistance being acquired after multiple rounds of chemotherapy. In contrast,
initial adenocarcinoma response rates rarely exceed 20% suggesting that
adenocarcinoma is innately resistant.
I hypothesized that chemoresistance is mediated by one or more signalling pathways
dependent on the expression of a single gene, and that these pathways could
ultimately be targeted therapeutically. As such I set out to determine the mechanisms
behind acquired resistance in SCLC and innate chemoresistance in lung
adenocarcinoma.
To address chemoresistance in SCLC, I first developed a cohort of patient derived
xenografts, obtained using Endobronchial Ultrasound-Guided Transbronchial Needle
Aspiration (EBUS-TBNA), a minimally invasive technique for biopsying lung cancer.
From this cohort of PDXs, I generated an in vivo model of acquired resistance by
treating mice with multiple rounds of chemotherapy. To identify mechanisms of
chemoresistance, gene expression arrays comparing resistant and naïve tumours were
performed, identifying differential expression in 767 genes. By comparing these
genes to those identified in acute response to platinum, we identified Notch 3 as a
potential target for the re-sensitization of acquired resistant SCLC to platinum.
To address innate chemoresistance, I developed a synthetic-lethal high throughput
xiv
siRNA screen using the innately resistant A549 lung adenocarcinoma cell line.
Optimisation of the screen was performed using a siRNA death control (PLK1),
which induced cell death in the absence of platinum, and a sensitization control
(MTOR), which enhanced cell death only in combination with a sublethal
concentration of carboplatin. These independent controls revealed that the screening
protocol performed within acceptable limits of variability, quality and reproducibility
as determined by Z’ factor analysis. Screening was then performed using a pool of
four siRNAs targeting a single gene in conjunction with vehicle treatment, or with
carboplatin. After screening 18,000 siRNAs targeting coding sequences of the whole
human genome, we identified 909 candidate targets based on fold change difference
between platinum and vehicle treatments, and statistical significance determined by
multiple t-test corrected for false discovery rate.
From the screen I identified and validated several therapeutic targets. Of these
Follistatin, an endogenous Activin/TGFβ superfamily ligand trap, was identified as a
potent platinum sensitization agent. Importantly, Follistatin also has the potential to
block Activin/TGBβ signaling in the setting of inflammation, fibrosis, renal injury,
cachexia and anemia, all of which are commonly seen in lung cancer patients treated
with platinum agents. I conclude that Follistatin therapy could improve the efficacy of
platinum-based chemotherapy in lung adenocarcinoma, while at the same time
ameliorate the systemic effects of both chemotherapy and malignancy. Additional material(s) submitted with thesis.