Abstract PD05-12: Combination of Notch Inhibitor MK-0752 and Endocrine Therapy for Early Stage ERα + Breast Cancer in a Presurgical Window Pilot Study

Abstract

Background: Breast tumor initiating cells (TIC) use Notch receptors/ligands with other pathways for self renewal, resulting in tumor proliferation and progression. We showed that Notch inhibition with gamma secretase inhibitors (GSI) potentiates the effects of tamoxifen (tam) in xenografts (Rizzo et al. Cancer Res 2008). It is unknown whether GSIs plus endocrine therapy result in modulation of Notch and other proliferation markers in human breast cancer. Our objective was to add short exposure of the GSI MK-0752 to ongoing tam or letrozole (letr) during the presurgical window to determine 1) feasibility, 2) safety/tolerance, and 3) impact on biomarkers. We report the initial cohort of this pilot study (ClinTrials. gov NCT00756717). Methods: Patients (pts) with early stage ERα + breast cancer were treated with 25 days of tam or letr. On day 15 MK-0752 was added to endocrine therapy (350 mg orally 3 days on, 4 days off, 3 days on), with definitive surgery day 25. Formalin fixed, paraffin embedded biopsies were obtained at baseline, day 14 and final surgery, with histologic confirmation of tumor content >50% and RNA extraction by standard methods. Q-PCR was done for Notch1, Notch3, Notch4, Deltex, Jagged1, c-myc, HEY1, HEY2, HES1, PS2, C-Myc, Cyclin A2, NOXA (pro-apoptotic protein), Ki67, Dicer-1, RPL13 (internal control). Ct averages for 3 replicates were used and mRNA levels were calculated by the 2ΔΔCt method. Baseline gene expression levels were used as comparators for days 14 and 25 levels in each pt. The first cohort of 10 pts was analyzed to determine if enough signals were present to justify expanding the cohort at this dose to 20 pts and possibly test a second cohort on an alternate MK-0752 dose/schedule. Results: The initial cohort of 10 pts completed all therapy (4 tam, 6 letr), all biopsies and definitive surgery on schedule. One other pt withdrew prior to starting MK-0752 due to hypertension. Toxicity was minimal: grade 1 periorbital edema/cough, nausea, and axillary paresthesias in 1 pt each; grade 1 facial rash, 2 pts; and grade 2 fatigue, 1 pt. There was no diarrhea or surgical complications. Significant changes occurred in molecular marker levels after MK-0752 plus tam/letr (day 25) vs. end of tam/letr alone (day 14) as follows: Ki67 mRNA decreased in 9/10 pts; Notch4 decreased, 10/10; NOXA increased, 6/10; and Notch1 decreased, 6/10. Other markers showed inter-individual variations and will be presented, along with results of the global gene expression profiling (in progress). Conclusions: The addition of a short exposure of the GSI MK-0752 to ongoing endocrine therapy was feasible, safe, and well tolerated in pts with ERα + early breast cancer prior to definitive surgery. It results in anti-proliferative and pro-apoptotic effects at the molecular level. Notch4, which plays a key role in breast TIC, was the most consistent molecular marker of response in this setting. This suggests a potential anti-TIC effect of this combination and a role in overcoming endocrine resistance. Accrual to the expanded cohort is underway. If findings are confirmed, the second study with alternate MK-0752 dose/schedule may commence. Funding: Swim Across America, Inc. (clinical trial costs); Merck (drug supply, profiling) Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD05-12.

p53 Modulates Notch Signaling in MCF‐7 Breast Cancer Cells by Associating With the Notch Transcriptional Complex Via MAML1

“…Moreover, knockdown of Notch‐1 or inhibition of γ‐secretase in T47D (Luminal B, ERα+, p53 mutant) and MDA‐MB231 (claudin‐low, ERα‐, p53 mutant) cells leads to upregulation of NOXA regardless of ER or p53 status (Rizzo et al, ). NOXA upregulation was observed in early stage ERα+ breast cancers in a pilot clinical trial of GSI MK‐0752 plus endocrine therapy (Albain et al, ). Thus, suppression of NOXA expression may be a key mechanism whereby Notch‐1 transmits a survival signal.…”

Targeting Notch, Hedgehog, and Wnt pathways in cancer stem cells: clinical update

“…In addition, combining GSIs with glucocorticoids 45 or antioestrogen agents 46 decreased intestinal toxicity in animal models, and intermittent administration of two different GSIs in combination with tamoxifen, letrozole or exemestane was well tolerated in pilot clinical studies. 47, 48 Thus, the advantages of GSIs include generally favourable tissue penetration, low cost, ease of administration and potential pan-Notch inhibitory activity. 19,23 Potential disadvantages are systemic toxicity and off-target effects, as γ-secretase has >90 substrates in addition to the Notch receptors; GSIs potentially inhibit the cleavage of all substrates, which might contribute to their toxicity and/or effectiveness in ways that are not currently understood.…”

“…46 As might be expected based on these interactions, combinations of anti-oestrogens and Notch inhibitors were highly effective in preclinical models of ER-positive breast cancer, 46,198 and have shown promise in pilot clinical trials in this disease. 47,48 …”

Notch Signalling in Breast Development and Cancer

“…Notch inhibition alone is unlikely to be sufficient to induce tumour regression, but shows promise in combination therapy ( Meurette et al, 2009 ; Brennan and Clarke, 2013 ; Proia et al, 2015 ). In clinical trials, GSIs have been combined with conventional chemotherapeutics and endocrine therapy, as well as radiotherapy to help improve radiosensitivity and reach metastatic cells in hard to access areas ( Table 1 ; Albain et al, 2010 ; ClinicalTrials.gov., 2016 , 2019a , b ; Lamy et al, 2017 ).…”