Retraction Note: An apoptosis-enhancing drug overcomes platinum resistance in a tumour-initiating subpopulation of ovarian cancer.

This Article has been retracted; see accompanying Retraction Note.

Birinapant sensitizes platinum-resistant carcinomas with high levels of cIAP to carboplatin therapy.

Platinum drugs are the frontline therapy in many carcinomas, including high-grade serous ovarian cancers. Clinically, high-grade serous carcinomas have an apparent complete response to carboplatin, but tumors invariably recur and response to platinum drugs diminishes over time. Standard of care prohibits re-administration of platinum drugs to these patients who are labeled as having platinum-resistant disease. In this stage patients are treated with non-platinum agents and outcomes are often poor. In vivo and in vitro data presented here demonstrate that this clinical dogma should be challenged. Platinum drugs can be an effective therapy even for platinum-resistant carcinomas as long as they are combined with an agent that specifically targets mechanisms of platinum resistance exploited by the therapy-resistant tumor subpopulations. High levels of cellular inhibitor of apoptosis proteins cIAP1 and 2 (cIAP) were detected in up to 50% of high-grade serous and non-high-grade serous platinum-resistant carcinomas. cIAP proteins can induce platinum resistance and they are effectively degraded with the drug birinapant. In platinum-resistant tumors with ≥22.4 ng of cIAP per 20 µg of tumor lysate, the combination of birinapant with carboplatin was effective in eliminating the cancer. Our findings provide a new personalized therapeutic option for patients with platinum-resistant carcinomas. The efficacy of birinapant in combination with carboplatin should be tested in high-grade serous carcinoma patients in a clinical trial.

An apoptosis-enhancing drug overcomes platinum resistance in a tumour-initiating subpopulation of ovarian cancer.

High-grade serous ovarian cancers (HGSCs) are deadly malignancies that relapse despite carboplatin chemotherapy. Here we show that 16 independent primary HGSC samples contain a CA125-negative population enriched for carboplatin-resistant cancer initiating cells. Transcriptome analysis reveals upregulation of homologous recombination DNA repair and anti-apoptotic signals in this population. While treatment with carboplatin enriches for CA125-negative cells, co-treatment with carboplatin and birinapant eliminates these cells in HGSCs expressing high levels of the inhibitor of apoptosis protein cIAP in the CA125-negative population. Birinapant sensitizes CA125-negative cells to carboplatin by mediating degradation of cIAP causing cleavage of caspase 8 and restoration of apoptosis. This co-therapy significantly improves disease-free survival in vivo compared with either therapy alone in tumour-bearing mice. These findings suggest that therapeutic strategies that target CA125-negative cells may be useful in the treatment of HGSC.

Epithelial stem cells of the prostate and their role in cancer progression.

Prostate cancer is a leading cause of cancer-related death in adult men. It can regress dramatically upon antihormonal therapy, but it often recurs in a more aggressive, androgen-independent form. Defining the prostate tissue stem cells (PrSCs) and their involvement in cancer initiation and maintenance may lead to better therapeutics. Using a tissue-regeneration model in which dissociated prostate epithelial cells mixed with inductive mesenchyme give rise to prostatic tubules, we have identified a small population of prostate cells that contains multiple stem cell characteristics. In this system, prostate cancer can be initiated by autocrine or paracrine growth factor signaling and intracellular overexpression of genes often found mutated in human prostate cancer. Using an in vitro prostate sphere assay, we further defined the PrSC population and demonstrated their self-renewal and multilineage differentiation capabilities. Microarray analyses of the stem- and non-stem-cell populations have assisted us in finding and evaluating additional markers that can better define the PrSC population and further delineate the different cell types of the prostate, including those that serve as the target cell for tumor initiation.

CA125 levels are a weak predictor of optimal cytoreductive surgery in patients with advanced epithelial ovarian cancer.

The utility of preoperative CA125 to predict optimal primary tumor cytoreduction in patients with advanced (stages IIIC and IV) epithelial ovarian cancer is controversial. In this paper, we retrospectively review patients with stage IIIC and IV epithelial ovarian cancer who underwent primary cytoreductive surgery from 1989 to 2001. Ninety-nine patients were identified and included in the analysis. All patients had preoperative CA125 levels measured. Operative and pathology reports were reviewed. Optimal cytoreduction was defined as largest volume of residual disease < 1 cm in maximal dimension. Mean values were compared with t-test on a log scale when needed. The optimal cut-point for discriminating between those with vs. without optimal cytoreduction was determined using the receiver operator curve (ROC) method. Optimal cytoreduction was achieved in 73% of patients. Among patients with optimal cytoreductive status the mean CA125 level was 569, while among patients with suboptimal cytoreduction the mean CA125 level was 1520 (P < 0.007). A CA125 level of 912 was identified as the optimal cut-point to distinguish the two groups. Using this CA125 level, the sensitivity of this test in predicting optimal cytoreduction was 58% and the specificity was 54%. The positive predictive value of CA125 for optimal cytoreduction was 78% and the negative predictive value was 31%. We conclude that CA125 level is a weak positive and negative predictor of optimal cytoreductive surgery in patients with advanced epithelial ovarian cancer. The CA125 level should not be used as a primary predictor of the outcome of cytoreductive surgery and should be viewed in the context of all other preoperative features.

FIGO stage III and IV uterine papillary serous carcinoma: impact of residual disease on survival.

The objective of this study was to assess the impact of surgical cytoreduction on the survival of patients with uterine papillary serous carcinoma (UPSC). Patients added to the institutional tumor registries between January 1980 and September 2001 with the diagnosis of UPSC were reviewed. The records of 43 patients who underwent surgical cytoreduction for FIGO stage III and IV disease were reviewed. The median survival of UPSC patients with microscopic residual disease was significantly improved compared to those with macroscopic residual disease following primary surgical cytoreduction. We conclude that primary surgical cytoreduction resulting in microscopic residual disease is associated with an improvement in recurrence-free survival and overall survival in women with UPSC.

Advances in the management of epithelial ovarian cancer.

More than 23,400 new cases of ovarian cancer and 13,900 deaths are expected in the United States this year. Epithelial ovarian cancer is the most common histologic type of ovarian malignancy. Although there have been advances in the chemotherapeutic treatment of ovarian cancer, the five year survival of women with advanced-stage disease is 25-30%. Because the disease is typically asymptomatic until the disease has metastasized and because effective screening strategies are not unavailable, 70-75% of women present with advanced-stage disease. Of ovarian cancer cases, 90-95% are sporadic and 5-10% associated with germ-line mutations, including BRCA1 and BRCA2. Known risk factors for ovarian cancer include nulliparity and a strong family history of ovarian cancer. The use of oral contraceptives is known to decrease the risk of ovarian cancer: five years of use will decrease the risk by 50%. The staging of ovarian cancer (according to the International Federation of Obstetrics and Gynecology) requires surgical exploration. Determining the extent of disease is essential to appropriate management. Survival in patients with metastatic disease is improved in those who undergo optimal primary cytoreductive surgery. Adjuvant chemotherapy is recommended in patients with high-risk, early-stage disease and all patients with advanced-stage disease. Standard chemotherapy is a combination of paclitaxel and carboplatin. Selected patients with recurrent disease can undergo secondary cytoreductive surgery. Second-line chemotherapy for patients who initially respond to paclitaxel and carboplatin and who have a prolonged disease progression-free intervals (longer than 12 months) can be re-treated with either drug or both. Those whose responses to initial therapy were less successful can be treated with other chemotherapeutic agents--e.g., liposomal doxorubicin, topotecan, etoposide, gemcitabine or taxotere.