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KRAS-Mutated, Estrogen Receptor-Positive Low-Grade Serous Ovarian Cancer: Unraveling an Exceptional Response Mystery
Shumei Kato1, Thomas McFall2, Kenta Takahashi3
1Center for Personalized Cancer Therapy and Moores Cancer Center, University of California San Diego, La Jolla, California, USA.
Abstract:
We report on a woman with aggressive estrogen receptor-positive, KRAS-mutated ovarian cancer who achieved a remarkable response to combination therapy with the MEK inhibitor (trametinib) and the aromatase inhibitor (letrozole), even though the disease had failed to respond to a combination of a PI3K inhibitor and different MEK inhibitor, as well as to trametinib and the estrogen modulator, tamoxifen, and to letrozole by itself. The mechanism of action for exceptional response was elucidated by in vitro experiments that demonstrated that the fact that tamoxifen can have an agonistic effect in addition to antagonist activity, whereas letrozole results only in estrogen depletion was crucial to the response achieved when letrozole was combined with an MEK inhibitor. Our current observations indicate that subtle variations in mechanisms of action of outwardly similar regimens may have a major impact on outcome and that such translational knowledge is critical for optimizing a precision medicine strategy. KEY POINTS: This report describes the remarkable response of a patient with KRAS-mutated, estrogen receptor-positive low-grade serous ovarian cancer treated with trametinib (MEK inhibitor) and letrozole (aromatase inhibitor), despite prior progression on similar agents including tamoxifen (estrogen modulator). In vitro investigation revealed that tamoxifen can have agonistic in addition to antagonistic effects, which could be the reason for the patient not responding to the combination of trametinib and tamoxifen. The current observations suggest that drugs with different mechanisms of action targeting the same receptor may have markedly different anticancer activity when used in combinations.
Insights
A patient with KRAS-mutated ovarian cancer responded well to trametinib and letrozole. This combination therapy, targeting MEK and estrogen, proved effective where other treatments failed, highlighting nuanced therapeutic strategies.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Estrogen receptor-positive ovarian cancer with KRAS mutations presents a therapeutic challenge.
- Prior treatments involving PI3K inhibitors, MEK inhibitors, estrogen modulators, and aromatase inhibitors showed limited efficacy in this patient.
- The patient had progressed on trametinib combined with tamoxifen, and on letrozole monotherapy.
Observation:
- A patient with aggressive estrogen receptor-positive, KRAS-mutated ovarian cancer experienced a significant clinical response to combination therapy with trametinib (MEK inhibitor) and letrozole (aromatase inhibitor).
- This response occurred despite prior disease progression on other regimens, including a PI3K inhibitor/MEK inhibitor combination, trametinib/tamoxifen, and letrozole monotherapy.
- In vitro studies were conducted to elucidate the mechanism behind the observed treatment response.
Findings:
- In vitro experiments revealed that tamoxifen exhibits both agonistic and antagonistic effects on estrogen receptors, unlike letrozole, which solely depletes estrogen.
- The distinct mechanisms of action, specifically estrogen depletion by letrozole versus the dual action of tamoxifen, were critical for the successful response when letrozole was combined with a MEK inhibitor.
- These findings suggest that subtle differences in drug mechanisms, even within the same drug class or targeting the same pathway, can significantly impact therapeutic outcomes.
Implications:
- Subtle variations in the mechanisms of action of seemingly similar therapeutic regimens can profoundly influence patient outcomes.
- Understanding these nuanced differences is crucial for optimizing precision medicine strategies in ovarian cancer treatment.
- This case underscores the importance of translational research in guiding the development of more effective combination therapies by considering the precise molecular actions of each drug component.
