A phase I trial of panobinostat and epirubicin in solid tumors with a dose expansion in patients with sarcoma

BACKGROUND

Treatment options for sarcoma are limited. Histone deacetylase inhibitors increase the efficacy of topoisomerase II inhibitors by promoting access to chromatin and by down-regulating DNA repair. Thus, combined panobinostat and epirubicin therapy was evaluated to treat refractory sarcoma.

PATIENTS AND METHODS

Patients with advanced solid tumors were enrolled in a 3 + 3 dose-escalation phase I trial of panobinostat given on days 1, 3, and 5 followed by 75 mg/m(2) of epirubicin on day 5 in 21-day cycles, with a dose expansion at maximum tolerated dose (MTD) in 20 sarcoma patients. Peripheral blood mononucleocyte histone acetylation was also evaluated.

RESULTS

Forty patients received 20-60 mg panobinostat. Dose-limiting toxicities included thrombocytopenia, febrile neutropenia, and fatigue at 60 mg, defining a panobinostat MTD at 50 mg. Four responses were seen in 37 assessable patients, all after progression on prior topoisomerase II inhibitors. For those with sarcoma, 12 of 20 derived clinical benefit (1 partial response and 11 stable disease, median overall survival 8.3 months), including 8 of 14 previously progressed on topoisomerase II therapy. Treatment benefits correlated with increased histone acetylation and decreased neutrophil count on day 5.

CONCLUSIONS

Panobinostat and epirubicin treatment is well tolerated and may reverse anthracycline resistance. Changes in histone acetylation and associated decrease in neutrophil count correlated with clinical benefit and warrant investigation as predictive biomarkers.

CLINICAL TRIAL

This trial is registered at www.Clinicaltrials.gov, Identifier: NCT00878904.

Abstract P5-09-13: HDAC inhibition re-sensitizes acquired hormone resistant cells to the cytotoxic effect of tamoxifen

Breast cancer still continues to be a major cause of cancer related deaths in women, second only to lung cancer. Administering anti-estrogens and aromatase inhibitors, both in the adjuvant and metastatic settings, in estrogen receptor (ER) positive disease, is one of the most effective treatment strategies. However, prolonged exposure to these drugs leads to the emergence of resistance in about 40% of those who initially respond. Hence, the emphasis of a multitude of studies is to understand the underlying mechanisms of this acquired resistance and implementing means to overcome it.

Recent studies have implicated epigenetic modulation of gene expression in the development of resistance to the anti-estrogen tamoxifen. A clinical trial conducted by our group has demonstrated the efficacy of combining the HDAC inhibitor vorinostat with tamoxifen in patients who had progressed on prior anti-estrogen therapies and showed a total 40% clinical benefit (19% objective response and 21% stable disease for more than 6 months). In an effort to identify patients most likely to benefit from this novel therapy, we sought to elucidate the mechanism behind the clinical efficacy of this combination.

To this end, we have generated an in vitro tamoxifen resistant cell line (TAMR) by long-term exposure of MCF7 cells to 4-hydroxy tamoxifen. Significantly reduced anti-proliferative effect of tamoxifen and other anti-estrogens in TAMR compared to the sensitive MCF7 cells demonstrates the establishment of resistance to anti-estrogens in this cell line. In TAMR cells, addition of an HDAC inhibitor reverts resistance to tamoxifen. Although estrogen receptor (ER) expression in TAMR cells appears unaltered, the classical genomic signaling of ER in these resistant cells is suppressed and unresponsive to ligands, as deduced from transcription of ER response genes and luciferase assay of an ERE-luciferase construct. However, the ER remains important, since siRNA mediated depletion of ER inhibits cell growth in TAMR cells. Treatment with the dual EGFR/Her2 kinase inhibitor or an AKT inhibitor significantly inhibits the growth of these cells only when combined with tamoxifen, indicating the importance of crosstalk between pathways. Furthermore, Akt and mTOR protein and activities are down regulated by HDAC inhibition, which are further reduced when combined with tamoxifen. SiRNA mediated depletion of ER leads to reduced Akt and mTOR activities which suggests that ER may act as a driver, possibly through its non-genomic function at the plasma membrane activating members of the growth factor signaling pathways.

Studies are ongoing to further characterize the interaction of HDAC and ER inhibition on these signaling pathways and to determine their significance to resistance.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-09-13.

Abstract P4-16-01: A novel approach to breast cancer prevention: Exploiting autologous fat grafting for the local delivery of cancer therapeutics

Background: Breast cancer remains a considerable health concern, despite major advances in the treatment and prevention of breast cancer. Inhibition of estrogen receptor signaling is one of the most effective therapies for patients with hormone receptor positive breast cancer. However, even after chemotherapy and hormonal therapy, local recurrence occurs frequently, and undesirable side effects lead to drug discontinuation in an estimated 40% of patients on adjuvant therapy.

Autologous fat transfer is an emerging therapy used in breast reconstruction to restore surgical deformities after lumpectomy, or to rebuild the breast following mastectomy. This is an attractive option for both radiated and non-radiated patients, as complication rates in both groups are exceedingly low. Fat is injected into the breast or surgical cavity to maximize its contact with local vascularized tissue, to promote re-vascularization and survival of the adipose tissue. Thus, fat cells are injected throughout the tissue surrounding the surgical margin. We hypothesize that harvested adipose tissue can be loaded with a lipophilic drug prior to its re-injection into the breast cavity and its surrounding tissue. With the release of drug from the transplanted adipose tissue over time, the local concentration of an anti-estrogen within the breast parenchyma would be increased and systemic toxicity may be minimized.

Method: Human adipose tissue was acquired from patients undergoing liposuction for autologous grafting. Tissue was washed with warm PBS, divided into 0.5 mL aliquots, and incubated in complete DMEM (10% FBS) containing increasing concentrations of 4-OH tamoxifen (0, 10, 20, or 40 uM) or fulvestrant (0, 0.1, 0.5, or 1.0 uM) for 12 hours. Following incubation, adipose tissue was washed thoroughly and co-cultured with MCF7 cells for 96 hours. Adipocyte co-cultured MCF7 were then collected and evaluated for proliferation, viability and effects on estrogen receptor signaling and compared to MCF7 directly exposed to anti-estrogens.

Results: When co-culturing tamoxifen- or fulvestrant-loaded human adipocytes with MCF7 breast cancer cells in vitro, we observed a dose-dependent reduction in cell proliferation (tamoxifen, 60% reduction; fulvestrant, 40% reduction) and viability (20%), comparable to directly drugged media. Examination of the molecular response to fulvestrant demonstrated a dose dependent down regulation of ER protein expression and activity (e.g. PgR and Cyclin D1). Currently, we are characterizing the pharmacokinetics of anti-estrogen uptake and release in both in vitro and in vivo.

Summary: Our preliminary data suggest that co-culturing human adipocytes with an anti-estrogen results in tumor growth inhibition and abrogation of estrogen receptor signaling. Human adipocytes used to fill the tumor bed cavity or mastectomy pocket could therefore be used as a vehicle to deliver anti-estrogens to residual tumor cells and prevent tumor regrowth. This method may be a novel technology to combine reconstructive surgery and anti-cancer therapy and prevention.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-16-01.