Purpose We sought to determine whether PI3K pathway mutation or activation state and rapamycin-induced feedback-loop activation of Akt is associated with rapamycin sensitivity or resistance. Experimental Design Cancer cell lines were tested for rapamycin-sensitivity, Akt phosphorylation and mTOR target inhibition. Mice injected with breast or neuroendocrine cancer cells and patients with neuroendocrine tumor (NET) were treated with rapalogs, and Akt phosphorylation was assessed. Results 31 cell lines were rapamycin-sensitive (RS) and 12 were relatively rapamycin-resistant (RR; IC50>100 nM). Cells with PIK3CA and/or PTEN mutations were more likely to be RS (p=0.0123). Akt phosphorylation (S473 and T308) was significantly higher in RS cells (p<0.0001). Rapamycin led to a significantly greater pathway inhibition and greater increase in p-Akt T308 (p<0.0001) and p-Akt S473 (p=0.0009) in RS cells. Rapamycin and everolimus significantly increased Akt phosphorylation but inhibited growth in an in vivo NET model (BON). In patients with NETs treated with everolimus and octreotide, progression-free survival correlated with p-Akt T308 in pretreatment (R=0.4762, p=0.0533) and on-treatment tumor biopsies (R=0.6041, p=0.0102). Patients who had a documented partial response were more likely to have an increase in p-Akt T308 with treatment compared to non-responders (p=0.0146). Conclusion PIK3CA/PTEN genomic aberrations and high p-Akt levels are associated with rapamycin sensitivity in vitro. Rapamycin-mediated Akt activation is greater in RS cells, with a similar observation in patients with clinical responses on exploratory biomarker analysis; thus feedback-loop activation of Akt is not a marker of resistance but rather may function as an indicator of rapamycin activity.

Background Our objective was to determine the clinicopathologic features of triple-negative (estrogen receptor, progesterone receptor, and human epidermal growth factor-2 receptor negative) breast cancer and their relationship to obesity in women drawn from a population with one of the highest obesity rates in the United States. Methods This retrospective study involved 620 White patients with invasive breast cancer in West Virginia. Hospital tumor registry, charts, and pathology records provided age at diagnosis, tumor histologic type, size, nodal status, and receptor status. Body mass index was calculated and a value of ≥30 was considered indicative of obesity. Results Triple-negative tumors occurred in 117 (18.9%) of the 620 patients, most often in association with invasive ductal carcinomas. Patients with triple-negative tumors were younger than those with other receptor types, 44.5% and 26.7%, respectively, being diagnosed at age <50 years (P = 0.0004). The triple-negative tumors were larger (P = 0.0003), most notably in the younger women, but small tumors (<2.0 cm) were more often accompanied by lymph node metastases. Obesity was present in 49.6% of those with triple-negative tumors but in only 35.8% of those with non-triple-negative tumors (P = 0.0098). Lymph node metastases were more frequently associated with T2 tumors in obese patients (P = 0.032) regardless of their receptor status. Conclusions Triple-negative breast cancers within a White, socioeconomically deprived, population occurred in younger women, with later stage at diagnosis, and in association with obesity, which itself has been associated with a poor prognosis in breast cancer.

Background Triple-negative breast cancer (TNBC) is an aggressive subtype shown to have a high risk of locoregional recurrence (LRR). The purpose of this study was to determine the impact of operation type on LRR in TNBC patients. Methods A total of 1325 patients with TNBC who underwent breast-conserving therapy (BCT) or mastectomy from 1980 to the present were identified. Clinical and pathological factors were compared by the chi-square test. LRR-free survival (LRRFS), distant metastasis-free survival, and overall survival were estimated by the Kaplan–Meier method. Multivariate analysis was performed by the Cox proportional hazard models. Results BCT was performed in 651 patients (49%) and mastectomy in 674 (51%). The mastectomy group had larger tumors, a higher incidence of lymphovascular invasion, and higher pathologic N stage (all P < 0.001). At 62-month median follow-up, LRR was seen in 170 (26%) in the BCT group and 203 (30%) in the mastectomy group. Five-year LRRFS rates were higher in the BCT group (76% vs. 71%, P = 0.032), as was distant metastasis-free survival (68% vs. 54%, P < 0.0001) and overall survival (74% vs. 63%, P < 0.0001). On multivariate analysis, T stage (hazard ratio [HR] 1.37, P = 0.006), high nuclear grade (HR 1.92, P = 0.002), lymphovascular invasion (HR 1.93, P < 0.0001), close/positive margins (HR 1.89, P < 0.0001), and use of non–anthracycline or taxane-based adjuvant chemotherapy (HR 2.01, P < 0.0001) increased the LRR risk, while age >50 years was protective (HR 0.73, P = 0.007). Operation type (mastectomy vs. BCT, HR 1.07, P = 0.55) was not statistically significant. Conclusions BCT is not associated with increased LRR rates compared to mastectomy. TNBC should not be considered a contraindication for breast conservation.

We tested the antitumor efficacy of mTOR catalytic site inhibitor MLN0128 in models with intrinsic or acquired rapamycin-resistance. Cell lines that were intrinsically rapamycin-resistant as well as those that were intrinsically rapamycinsensitive were sensitive to MLN0128 in vitro. MLN0128 inhibited both mTORC1 and mTORC2 signaling, with more robust inhibition of downstream 4E-BP1 phosphorylation and cap-dependent translation compared to rapamycin in vitro. Rapamycin-sensitive BT474 cell line acquired rapamycin resistance (BT474 RR) with prolonged rapamycin treatment in vitro. This cell line acquired an mTOR mutation (S2035F) in the FKBP12-rapamycin binding domain; mTORC1 signaling was not inhibited by rapalogs but was inhibited by MLN0128. In BT474 RR cells, MLN0128 had significantly higher growth inhibition compared to rapamycin in vitro and in vivo. Our results demonstrate that MLN0128 may be effective in tumors with intrinsic as well as acquired rapalog resistance. mTOR mutations are a mechanism of acquired resistance in vitro; the clinical relevance of this observation needs to be further evaluated.

#6099 Background: Our objective was to determine the clinico-pathological features of triple-negative (estrogen, progesterone and HER-2 receptor negative) breast cancer and their relationship to obesity in women drawn from a population with one of the highest obesity rates in the United States.&#x2028; Methods: This retrospective study involved 620 white patients with invasive breast cancer in West Virginia. Hospital tumor registry, charts, and pathology records provided age at diagnosis, tumor histologic type, size, and nodal status, and receptor status. Body mass index (BMI) was calculated and a value of ≥30 considered indicative of obesity.&#x2028; Results: Triple-negative tumors occurred in 117 (18.9%) of the 620 patients, most often in association with invasive ductal carcinomas. Patients with triple-negative tumors were younger than those with other receptor types, 44.5% and 26.7%, respectively, being diagnosed before age 50 years (P = 0.0004). The triple-negative tumors were larger (P = 0.0003), most notably in the younger women, but small tumors (&lt;2.0 cm) were more often accompanied by lymph node metastases. Obesity was present in 49.6% of those with triple-negative tumors, but only 35.8% of those with non-triple-negative tumors (P = 0.0098). Lymph node metastases were more frequently associated with T2 tumors in obese patients (P = 0.032) regardless of their receptor status.&#x2028; Conclusions: Triple-negative breast cancers within a white, socioeconomically-deprived, population occurred in younger women, with later stage at diagnosis, and in association with obesity. The elevated adipokine production which is present in obesity may exert tumor proliferative and angiogenic effects that contribute to an aggressive phenotype. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6099.