0      0

eSymposia | Genomic Stability and DNA Repair


Acquired Resistance To BRAF Inhibitor Sensitizes Melanoma Cells To Chk1 Inhibition-Induced Replication Stress


Sep 21, 2020 12:00am ‐ Sep 21, 2020 12:00am

Description

Acquired Resistance To BRAF Inhibitor Sensitizes Melanoma Cells To Chk1 Inhibition-Induced Replication Stress Carvalho, D.G.1,*, Kenski, J.C.N.2,*, Rajão, M.A.1, Viola, J.P.B.1, Peeper, D.S.2, Possik, P.A.1 1Brazilian National Cancer Institute, Rio de Janeiro, Brazil; 2The Netherlands Cancer Institute, Amsterdam, The Netherlands *These authors contributed equally to this work BRAF mutations are frequent in melanoma and contribute to disease progression. BRAF inhibitor (BRAFi) treatment leads to rapid regression of melanoma metastases. However, therapy resistance is imminent and represents an important clinical challenge, underscoring the need for new therapeutic targets. Checkpoint kinase 1 (Chk1) is essential in cell cycle regulation and DNA damage response signaling, and is currently explored as a potential target in cancer. Here, we investigated Chk1 as a therapeutic target in BRAF inhibitor-resistant (BRAFiR) melanomas using GDC0575, a specific Chk1 inhibitor (Chk1i). We demonstrated that BRAFiR cells are hypersensitive to Chk1i compared to their respective treatment-naïve melanoma cells. The monitoring of cell cycle progression using a fluorescent cell cycle indicator system showed that a high percentage of BRAFiR cells are unable to complete cell division upon Chk1 inhibition. These data also indicated that S phase progression is crucial for Chk1i-induced cytotoxicity. Bromodeoxyuridine staining followed by flow cytometry showed that Chk1i-treated BRAFiR cells partially failed to incorporate nucleotides during S phase, whereas this effect was minimum in treatment-naïve cells. However, DNA fibers assay revealed decreased fork speed rate for both treatment-naïve and BRAFiR cells upon Chk1i treatment. Finally, we observed that Chk1i induced a greater increase in pRPA and yH2AX levels in BRAFiR cells than in treatment-naïve melanoma cells. Although Chk1i induces replication stress in both BRAFiR and treatment-naïve, we identified that these effects are more pronounced in BRAFiR cells, which accumulated higher levels of DNA damage, suggesting that these cells die after failing to recover from Chk1i-induced replication stress. These observations may help to identify biomarkers for Chk1i sensitivity and contribute to the development of more efficient therapeutic approaches for BRAFiR melanomas. Supported by: MS/INCA, CNPq, ICGEB, FAPERJ

Speaker(s):

You must be logged in and own this session in order to post comments.

Print Certificate
Completed on: token-completed_on
Print Transcript
Please select the appropriate credit type:
/
test_id: 
credits: 
completed on: 
rendered in: 
* - Indicates answer is required.
token-content

token-speaker-name
token-index
token-content
token-index
token-content
token-index
token-content
token-index
token-content
token-index
token-content
token-index
token-content
/
/
token-index
token-content
token-index
token-content