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T-Darpp overexpression in HER2-positive breast cancer confers a survival advantage in lapatinib.

ABSTRACT: Drug resistance is a major barrier to successful cancer treatment. For patients with HER2-positive breast cancer who initially respond to therapy, the majority develop resistance within one year of treatment. Patient outcomes could improve significantly if we can find and exploit common mechanisms of acquired resistance to different targeted therapies. Overexpression of t-Darpp, a truncated form of the dual kinase/phosphatase inhibitor Darpp-32, has been linked to acquired resistance to trastuzumab, a front-line therapy for HER2-positive breast cancer. Darpp-32 reverses t-Darpp's effect on trastuzumab resistance. In this study, we examined whether t-Darpp could be involved in resistance to lapatinib, another HER2-targeted therapeutic. Lapatinib-resistant SKBR3 cells (SK/LapR) showed a marked change in the Darpp-32:t-Darpp ratio toward a predominance of t-Darpp. Overexpression of t-Darpp alone was not sufficient to confer lapatinib resistance, but cells that overexpress t-Darpp partially mimicked the molecular resistance phenotype observed in SK/LapR cells exposed to lapatinib. SK/LapR cells failed to down-regulate Survivin and failed to induce BIM accumulation in response to lapatinib; cells overexpressing t-Darpp exhibited only the failed BIM accumulation. t-Darpp knock-down reversed this phenotype. Using a fluorescence-based co-culture system, we found that cells overexpressing t-Darpp formed colonies in lapatinib within 3-4 weeks, whereas parental cells in the same co-culture did not. Overall, t-Darpp appears to mediate a survival advantage in lapatinib, possibly linked to failed lapatinib-induced BIM accumulation. t-Darpp might also be relevant to acquired resistance to other cancer drugs that rely on BIM accumulation to induce apoptosis.

SUBMITTER: Christenson JL

PROVIDER: S-EPMC4741754 | biostudies-literature | 2015 Oct

REPOSITORIES: biostudies-literature

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t-Darpp overexpression in HER2-positive breast cancer confers a survival advantage in lapatinib.

Christenson Jessica L JL Denny Erin C EC Kane Susan E SE

Oncotarget 20151001 32

Drug resistance is a major barrier to successful cancer treatment. For patients with HER2-positive breast cancer who initially respond to therapy, the majority develop resistance within one year of treatment. Patient outcomes could improve significantly if we can find and exploit common mechanisms of acquired resistance to different targeted therapies. Overexpression of t-Darpp, a truncated form of the dual kinase/phosphatase inhibitor Darpp-32, has been linked to acquired resistance to trastuzu ...[more]

PMID: 26430732

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Project description:The cost-effectiveness of first-line treatment with lapatinib plus letrozole for postmenopausal women with hormone receptor-positive (hr+), human epidermal growth factor receptor 2-positive (her2+) metastatic breast cancer (mbc) has not been assessed from the Canadian health care system and societal perspectives.A partitioned survival analysis model with 3 health states (alive, pre-progression; alive, post-progression; dead) was developed to estimate direct and indirect costs and quality-adjusted life years (qalys) with lapatinib-letrozole, letrozole, anastrozole, or trastuzumab-anastrozole as first-line treatment. Clinical inputs for lapatinib-letrozole and letrozole were taken from the EGF30008 trial (NCT00073528). Clinical inputs for anastrozole and trastuzumab-anastrozole were taken from a network meta-analysis of published studies. Drug costs were obtained from the manufacturer's price list, the Quebec list of medications, and imsBrogan. Other costs were taken from the Ontario Health Insurance Plan's Schedule of Benefits and Fees and published studies. A 10-year time horizon was used. Costs and qalys were discounted at 5% annually. Deterministic and probabilistic sensitivity analyses were performed to assess the effects of changes in model parameters.Quality-adjusted life years gained with lapatinib-letrozole were 0.236 compared with trastuzumab-anastrozole, 0.440 compared with letrozole, and 0.568 compared with anastrozole. Assuming a health care system perspective, incremental costs were $5,805, $67,029, and $67,472 respectively. Given a cost per qaly threshold of $100,000, the probability that lapatinib-letrozole is preferred was 21% compared with letrozole, 36% compared with anastrozole, and 68% compared with trastuzumab-anastrozole. Results from the societal perspective were similar.In postmenopausal women with hr+/her2+ mbc receiving first-line treatment, lapatinib-letrozole may not be cost-effective compared with letrozole or anastrozole, but may be cost-effective compared with trastuzumab-anastrozole.

Dataset Information

T-Darpp overexpression in HER2-positive breast cancer confers a survival advantage in lapatinib.

Publications

t-Darpp overexpression in HER2-positive breast cancer confers a survival advantage in lapatinib.

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