Abstract P3-04-23: Combination therapy of targeted anticancer pathways and estrogen receptor ligands and their responses in de novo andtamoxifen resistant cell models

Approximately 75% of breast cancers are classified as Estrogen Receptor positive (ER+). Tamoxifen, a selective estrogen receptor modulator (SERM), is the standard of care for many of these ER+ breast cancer patients. Unfortunately, tamoxifen resistance occurs in almost 50% of patients within 5 years of treatment, and endocrine-independence accompanying resistance also negates the effects of aromatase inhibitors. Combination therapy is increasingly used in non-cytotoxic therapeutic approaches in many types of cancer. The potential exists that endocrine resistance can be lessened, eliminated, or overcome through targeted therapy in combination with endocrine therapy. Inhibition of kinase signaling (e.g. via CDK4/6 or PI3K) and other pathways (e.g. HSP90) are expected to be effective in combination with endocrine therapy. We have discovered a variety of ER ligands with potential as endocrine therapeutic agents, based upon a single chemical scaffold with a diverse set of pharmacological responses: including SERMs, selective ER downregulators (SERDs), selective estrogen mimics (SEMs), and selective human ER partial agonists (ShERPAs). To predict which agents in combination with these endocrine-targeted ligands would be of potential therapeutic benefit it was necessary to develop 3D spheroidal cultures of ER+ breast cancer cell lines: including endocrine-dependent lines; and cell lines made endocrine-independent either by extended exposure to tamoxifen or extended deprivation of estradiol. In contrast to 2D cultures, drug response in 3D spheroidal cell cultures was predictive of response to treatment in mouse xenograft studies. Growth of endocrine-dependent cell lines was, as expected, inhibited by SERDs; and endocrine-independent, tamoxifen-resistant cell lines were also sensitive to SERD treatment, although one cell line was largely resistant. Growth of all three tamoxifen-resistant cell lines was inhibited by SEMs/ShERPAs. Importantly, regardless of the type of endocrine therapeutic agent studied, concentrations leading to saturation of the target (ER) did not cause cell death. Equally, all endocrine therapies studied benefited from combination treatment with other agents, leading to enhanced cell death.

Citation Format: Gutgesell LM, Xiong R, Thatcher GRJ, Tonetti DA. Combination therapy of targeted anticancer pathways and estrogen receptor ligands and their responses in de novo andtamoxifen resistant cell models [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-04-23.

2-(4-Hydroxyphenyl)-Benzo[b]thiophen-6-ol, an Estrogen-Like Compound, Induces Apoptosis in T47D/PKCα Breast Cancer Cells

Background: Tamoxifen (TAM) treatment failure is a major obstacle encountered in the clinical setting. Our lab has previously shown that constitutive overexpression of PKCα imparts a TAM resistant/ hormone independent phenotype in the T47D:A18 breast cancer cell line. Furthermore 17β-estradiol (E2) inhibits tumor growth in vivo as well as inhibits colony formation when cells are grown in 3D Matrigel (Zhang, 2009). Before TAM treatment was introduced, breast cancer patients received high-dose E2 and diesthystilbesterol (DES) treatment. DES treated patients may have a survival advantage over TAM treated patients in the long term (Peethambaram,1999). Others have shown that E2 can have inhibitory effects on MCF-7 cells both in vitro and in vivo (Lewis-Wambi, 2009). Taken together, this suggests an estrogenic compound may be efficacious for TAM-resistant breast cancer. The present study was designed to evaluate the effect of an estrogenic compound, 2-(4-hydroxyphenyl)-benzo[b]thiophen-6-ol (BTC), related to the SERMs raloxifene and arzoxifene, on the T47D:A18/PKCα breast cancer cell line.Methods: To determine if BTC can activate estrogen regulated genes we preformed an ERE-luciferase reporter assay 24 hours after BTC treatment. 3D Matrigel colony formation assay was performed to determine if BTC could inhibit colony formation. Colonies were stained and counted on day 10. To determine if apoptosis was occurring, cells were grown in Matrigel and the TUNEL Assay was performed on Day 6.Results: T47D:A18/PKCα cells showed a 31-fold induction in ERE-luciferase reporter activity when treated with BTC (10-7M) compared to 7-fold induction when treated with E2. In the T47D:A18/Neo parental cell line, BTC induced a 40-fold induction whereas estradiol induced a 96-fold induction. In the Matrigel colony formation assay T47D:A18/PKCα cells formed significantly fewer colonies when treated with BTC. Conversely, in the T47D:A18/Neo parental cell line BTC enhanced colony formation similar to E2 treatment. Our results indicate that BTC was able to induce significant apoptosis on day 6 (P= 0.038) as determined by the TUNEL Assay. Therefore BTC acts similarly to estradiol by inhibiting T47D:A18/PKCα colony formation and inducing apoptosis when cells are grown in Matrigel.Conclusion: These findings suggest that BTC is a potential lead compound in the treatment of PKCα overexpressing breast cancer. Furthermore, BTC was shown to be a potent inducer of the cytoprotective enzyme NQO1 in the Hepa 1c1c7 cell system as well as a strong activator of antioxidant responsive elements (Yu, 2007) indicating it may have the added benefit of chemoprotective effects which are absent in estradiol treatment. Further understanding of the mechanism in which BTC induces apoptosis in the T47D:A18/PKCα cell line may result in a clinical advantage to estradiol treatment including fewer side effects.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5140.

Extranodal Ki-1 lymphoma in a renal transplant patient

THe Ki-1 (CD 30) antigen has been identified as a marker of a subset of large cell anaplastic non-Hodgkin's lymphoma that may have a more favourable prognosis. We describe an immunosuppressed renal transplant patient who developed primary extranodal large cell anaplastic Ki-1 lymphoma of T-cell phenotype confined to the sigmoid colon. The patient was treated with local resection of the sigmoid colon and reduction of immunosuppression and at two year follow-up remains free of recurrence. It is recognised that long term immunosuppression in post transplant patients increases the risk of certain malignancies. Localised gut lymphoma may be amenable to local resection as a curative procedure.

Comparison of three immunosuppressive regimens in cadaver renal transplantation: long-term cyclosporine, short-term cyclosporine followed by azathioprine and prednisolone, and azathioprine and prednisolone without cyclosporine

We conducted a randomized trial in seven Australian hospitals of the efficacy and safety of three immunosuppressive regimens after first transplantation of a cadaver kidney: long-term cyclosporine, short-term (three months) cyclosporine followed by azathioprine and prednisolone, and azathioprine and prednisolone without cyclosporine. Patients assigned to long-term cyclosporine (n = 138) or short-term cyclosporine followed by azathioprine and prednisolone (n = 141) had similar actuarial 12-month survival (98.4 vs. 96.4 percent) and graft survival (83.9 vs. 82.1 percent). Patients assigned to receive only azathioprine and prednisolone (n = 138), with optional use of antithymocyte globulin, had a significantly poorer survival rate (91.3 percent, P = 0.015) because of deaths from cardiac causes and infection, but their graft survival of 76.0 percent (P = 0.31) did not differ significantly from that of either group receiving cyclosporine. After the switch from cyclosporine to azathioprine and prednisolone, 15 percent of patients had reversible rejection episodes, but the frequency of rejection and graft loss did not differ from that in the long-term cyclosporine group. After the change to azathioprine and prednisolone, serum creatinine levels declined in nearly all patients, so that after three months they were comparable to those in the group receiving azathioprine and prednisolone only, and significantly lower than those in the group receiving long-term cyclosporine therapy (P less than 0.003). We conclude that the two cyclosporine regimens result in comparable patient and graft survival, but that changing to azathioprine and prednisolone at three months improves graft function.