Carlos M. Telleria

Ovarian Cancer Research in the Post Genomic Era — Challenges and Opportunities | InTechOpen, Published on: 2016-03-02. Authors: Alicia A. Goyeneche and Carlos M. Telleria

Antiprogestins constitute a group of compounds, developed since the early 1980s, that bind progesterone receptors with different affinities. The first clinical uses for antiprogestins were in reproductive medicine, e.g., menstrual regulation, emergency contraception, and termination of early pregnancies. These initial applications, however, belied the capacity for these compounds to interfere with cell growth. Within the context of gynecological diseases, antiprogestins can block the growth of and kill gynecological-related cancer cells, such as those originating in the breast, ovary, endometrium, and cervix. They can also interrupt the excessive growth of cells giving rise to benign gynecological diseases such as endometriosis and leiomyomata (uterine fibroids). In this article, we present a review of the literature providing support for the antigrowth activity that antiprogestins impose on cells in various gynecological diseases. We also provide a summary of the cellular and molecular mechanisms reported for these compounds that lead to cell growth inhibition and death. The preclinical knowledge gained during the past few years provides robust evidence to encourage the use of antiprogestins in order to alleviate the burden of gynecological diseases, either as monotherapies or as adjuvants of other therapies with the perspective of allowing for long-term treatments with tolerable side effects. The key to the clinical success of antiprogestins in this field probably lies in selecting those patients who will benefit from this therapy. This can be achieved by defining the genetic makeup required – within each particular gynecological disease – for attaining an objective response to antiprogestin-driven growth inhibition therapy. Free Spanish abstract A Spanish translation of this abstract is freely available at http://www.reproduction-online.org/content/149/1/R15/suppl/DC1. Abstract Antiprogestins constitute a group of compounds, developed since the early 1980s, that bind progesterone receptors with different affinities. The first clinical uses for antiprogestins were in reproductive medicine, e.g., menstrual regulation, emergency contraception, and termination of early pregnancies. These initial applications, however, belied the capacity for these compounds to interfere with cell growth. Within the context of gynecological diseases, antiprogestins can block the growth of and kill gynecological-related cancer cells, such as those originating in the breast, ovary, endometrium, and cervix. They can also interrupt the excessive growth of cells giving rise to benign gynecological diseases such as endometriosis and leiomyomata (uterine fibroids). In this article, we present a review of the literature providing support for the antigrowth activity that antiprogestins impose on cells in various gynecological diseases. We also provide a summary of the cellular and molecular mechanisms reported for these compounds that lead to cell growth inhibition and death. The preclinical knowledge gained during the past few years provides robust evidence to encourage the use of antiprogestins in order to alleviate the burden of gynecological diseases, either as monotherapies or as adjuvants of other therapies with the perspective of allowing for long-term treatments with tolerable side effects. The key to the clinical success of antiprogestins in this field probably lies in selecting those patients who will benefit from this therapy. This can be achieved by defining the genetic makeup required – within each particular gynecological disease – for attaining an objective response to antiprogestin-driven growth inhibition therapy. Free Spanish abstract A Spanish translation of this abstract is freely available at http://www.reproduction-online.org/content/149/1/R15/suppl/DC1.

We have known for quite some time that tumor heterogeneity does exist among patients diagnosed with the same histo-pathological type of a particular cancer, and between the primary tumor and the metastatic tissues within the same patient. This outstanding article reveals, using single-cell genome sequencing, that heterogeneity exists also within each tumor and at the single-cellular level. Furthermore, the study suggests that most bulky genetic changes take place early on during tumor evolution; in contrast, highly frequent point mutations occur along disease progression. Although the studies were done in breast cancer, it is highly likely that the concept does apply for most human cancers. The question that arises from these studies is, "which cell type, within the heterogeneous cell population composing a primary tumor, should be targeted to interrupt the evolution of the disease?"

Antiprogestin compounds have been shown to be effective in blocking the growth of ovarian cancer cells of different genetic backgrounds. Herein we studied the anti-ovarian cancer effect of a series of antiprogestins sharing the chemical backbone of the most characterized antiprogestin, mifepristone, but with unique modifications in position C-17 of the steroid ring. We assessed the effect of mifepristone-like antiprogestins on the growth of ovarian cancer cells sensitive to the standard combination therapy cisplatin-paclitaxel or made double-resistant upon six cycles of pulse-selection with the drugs used at clinically relevant concentrations and exposure times.

We have previously shown that the antiprogestin and antiglucocorticoid mifepristone inhibits the growth of ovarian cancer cells. In this work, we hypothesized that cellular stress caused by mifepristone is limited to cytostasis and that cell killing is avoided as a consequence of the persistent activity of the PI3K/Akt survival pathway. To investigate the role of this pathway in mifepristone-induced growth inhibition, human ovarian cancer cells of various histological subtypes and genetic backgrounds were exposed to cytostatic doses of mifepristone in the presence or absence of the PI3K inhibitor, LY294002. The activation of Akt in ovarian cancer cells, as marked by its phosphorylation on Ser473, was not modified by cytostatic concentrations of mifepristone, but it was blocked upon treatment with LY294002. The combination mifepristone/LY294002, but not the individual drugs, killed ovarian cancer cells via apoptosis, as attested by genomic DNA fragmentation and cleavage of caspase-3, and the concomitant downregulation of antiapoptotic proteins Bcl-2 and XIAP. From a pharmacological standpoint, when assessing cell growth inhibition using a median-dose analysis algorithm, the interaction between mifepristone and LY294002 was synergistic. The lethality caused by the combination mifepristone/LY294004 in 2-dimensional cell cultures was recapitulated in organized, 3-dimensional spheroids. This study demonstrates that mifepristone and LY294002 when used individually cause cell growth arrest; yet, when combined, they cause lethality.

Background: Changes in cell shape and plasticity in cytoskeletal dynamics are critically involved in cell adhesion, migration, invasion and the overall process of metastasis. Previous work in our laboratory demonstrated that the synthetic steroid mifepristone inhibited the growth of highly metastatic cancer cells, while simultaneously causing striking changes in cellular morphology. Here we assessed whether such morphological alterations developed in response to cytostatic concentrations of mifepristone are reversible or permanent, involve rearrangement of cytoskeletal proteins, and/or affect the adhesive capacity of the cells. Methods: Cancer cell lines of the ovary (SKOV-3), breast (MDA-MB-231), prostate (LNCaP), and nervous system (U87MG) were exposed to cytostatic concentrations of mifepristone and studied by phase-contrast microscopy. The transient or permanent nature of the cytostasis and morphological changes caused by mifepristone was assessed, as well as the rearrangement of cytoskeletal proteins. De-adhesion and adhesion assays were utilized to determine if mifepristone-arrested and morphologically dysregulated cells had abnormal de-adhesion/adhesion dynamics when compared to vehicle-treated controls. Results: Mifepristone-treated cells displayed a long, thin, spindle-like shape with boundaries resembling those of loosely adhered cells. Growth arrest and morphology changes caused by mifepristone were reversible in SKOV-3, MDA-MB-231 and U87MG, but not in LNCaP cells that instead became senescent. All cancer cell types exposed to mifepristone displayed greatly increased actin ruffling in association with accelerated de-adhesion from the culture plate, and delayed adhesion capacity to various extracellular matrix components. Conclusions: Cytostatic concentrations of mifepristone induced alterations in the cellular structure of a panel of aggressive, highly metastatic cancer cells of different tissues of origin. Such changes were associated with re-distribution of actin fibers that mainly form non-adhesive membrane ruffles, leading to dysregulated cellular adhesion capacity.

A new carboxy-monofunctionalized tertraarylporphyrin has been tested for cytotoxicity toward OV2008 human ovarian cancer cells. This compound acutely inhibits growth of ovarian cancer cells upon exposure to ambient light while suppresses long-term clonogenic survival of cells under both dark and light stimulated conditions. Because of the variable length of the linkage between the anthraquinone and porphyrin moieties, the synthesized monocarboxylated porphyrin presents a versatile scaffold for fine-tuning of the photoelectron transfer in the quinone-porphyrin conjugate. To demonstrate its synthetic value, we converted the carboxy derivative to its amino counterpart.

The high mortality rate caused by ovarian cancer has not changed for the past thirty years. Although most patients diagnosed with this disease respond to cytoreductive surgery and platinum-based chemotherapy and undergo remission, foci of cells almost always escape therapy, manage to survive, and acquire the capacity to repopulate the tumor. Repopulation of ovarian cancer cells that escape front-line chemotherapy, however, is a poorly understood phenomenon. Here I analyze cancer-initiating cells, transitory senescence, reverse ploidy, and cellular dormancy as putative players in ovarian cancer cell repopulation. As part of the standard of care, ovarian cancer patients do not receive treatment between primary cytotoxic therapy and clinical relapse. Understanding the mechanisms driving cellular escape from chemotherapy should lead to the development of low toxicity, chronic treatment approaches that can be initiated right after primary therapy to interrupt cell repopulation and disease relapse by keeping it dormant and, therefore, subclinical.

Background: Advanced ovarian cancer is treated with cytoreductive surgery and combination platinum- and taxane-based chemotherapy. Although most patients have acute clinical response to this strategy, the disease ultimately recurs. In this work we questioned whether the synthetic steroid mifepristone, which as monotherapy inhibits the growth of ovarian cancer cells, is capable of preventing repopulation of ovarian cancer cells if given after a round of lethal cisplatin-paclitaxel combination treatment.Methods: We established anin vitroapproach wherein ovarian cancer cells with various sensitivities to cisplatin or paclitaxel were exposed to a round of lethal doses of cisplatin for 1 h plus paclitaxel for 3 h. Thereafter, cells were maintained in media with or without mifepristone, and short- and long-term cytotoxicity was assessed.Results: Four days after treatment the lethality of cisplatin-paclitaxel was evidenced by reduced number of cells, increased hypodiploid DNA content, morphological features of apoptosis, DNA fragmentation, and cleavage of caspase-3, and of its downstream substrate PARP. Short-term presence of mifepristone either enhanced or did not modify such acute lethality. Seven days after receiving cisplatin-paclitaxel, cultures showed signs of relapse with escaping colonies that repopulated the plate in a time-dependent manner. Conversely, cultures exposed to cisplatin-paclitaxel followed by mifepristone not only did not display signs of repopulation following initial chemotherapy, but they also had their clonogenic capacity drastically reduced when compared to cells repopulating after cisplatin-paclitaxel.Conclusions: Cytostatic concentrations of mifepristone after exposure to lethal doses of cisplatin and paclitaxel in combination blocks repopulation of remnant cells surviving and escaping the cytotoxic drugs.