Nanoparticle delivery of diphtheria toxin-encoding DNA selectively expressed in ovarian cancer cells reduced the burden of ovarian tumors in mice, and researchers expect this therapy could be tested in humans within 18 to 24 months, according to a report in Cancer Research, a journal of the American Association for Cancer Research.

Although early stage ovarian cancer can be treated with a combination of surgery followed by chemotherapy, there are currently no effective treatments for advanced ovarian cancer that has recurred after surgery and primary chemotherapy. Therefore, the majority of treated early stage cancers will relapse.

“This report is definitely a reason to hope. We now have a potential new therapy for the treatment of advanced ovarian cancer that has promise for targeting tumor cells and leaving healthy cells healthy,” said lead researcher Janet Sawicki, Ph.D., a professor at the Lankenau Institute for Medical Research.

Sawicki and colleagues at the Massachusetts Institute of Technology evaluated the therapeutic efficacy of a cationic biodegradable beta-amino ester polymer as a vector for the nanoparticle delivery of a DNA encoding diphtheria toxin suicide gene. These nanoparticles were injected into mice with primary or metastatic ovarian tumors.

To test the efficacy of this technique, the researchers measured tumor volume before and after treatment. They found that while treated tumors increased 2-fold, this was significantly less than the between 4.1-fold and 6-fold increase in control mice.

Furthermore, four of the treated tumors failed to grow at all, while all control tumors increased in size. Administration of nanoparticles to three different ovarian cancer mouse models prolonged lifespan by nearly four weeks and suppressed tumor growth more effectively, and with minimal non-specific cytotoxicity, than in mice treated with clinically relevant doses of cisplatin and paclitaxel.

Edward Sausville, M.D., Ph.D., an associate editor of Cancer Research and associate director for clinical research at the Greenebaum Cancer Center at the University of Maryland, said this report illustrates significant progress in targeted therapy.

“In oncology we have been studying ways to kill tumors for a long time, but much of this has run up against the real estate principle of location, location, location,” he said. “In other words, an effective therapy is not effective if it cannot get to the target.”

Sausville said a major accomplishment of this research is the multiple ways it can target ovarian cancer cells, as scientists were able to deliver diphtheria toxin genes, using a nanoparticle, to the actual tumor site (peritoneum) with a basis for selective activity in the cancer cells (how the toxin genes were regulated once inside the cells).

“A real plus of a cancer therapy like this is not just the functionality of the nanoparticle construct molecule, but the ability to deliver the toxin to the tumor cells,” said Sausville, who agrees that inception of clinical trials could be just 18 months away.

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The mission of the American Association for Cancer Research is to prevent and cure cancer. Founded in 1907, AACR is the world’s oldest and largest professional organization dedicated to advancing cancer research. The membership includes more than 28,000 basic, translational and clinical researchers; health care professionals; and cancer survivors and advocates in the United States and nearly 90 other countries. The AACR marshals the full spectrum of expertise from the cancer community to accelerate progress in the prevention, diagnosis and treatment of cancer through high-quality scientific and educational programs. It funds innovative, meritorious research grants. The AACR Annual Meeting attracts more than 17,000 participants who share the latest discoveries and developments in the field. Special conferences throughout the year present novel data across a wide variety of topics in cancer research, treatment and patient care. The AACR publishes six major peer-reviewed journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; Cancer Epidemiology, Biomarkers & Prevention; and Cancer Prevention Research. The AACR also publishes CR, a magazine for cancer survivors and their families, patient advocates, physicians and scientists. CR provides a forum for sharing essential, evidence-based information and perspectives on progress in cancer research, survivorship and advocacy.

UCSF researchers have identified a new “feed-forward” pathway linking estrogen receptors in the membrane of the uterus to a process that increases local estrogen levels and promotes cell growth.

The research is significant in helping determine why tamoxifen and other synthetic estrogens are linked to increased rates of endometriosis and uterine cancer, and identifies a pathway that could be targeted in drug therapies for those diseases, researchers say.

Findings are published in the July 1, 2009 issue of “Cancer Research,” the journal of the American Association for Cancer Research. The paper also can be found online at http://cancerres.aacrjournals.org/current.shtml.

The research found that when activated by estrogens, endometrial cells obtained from patients suffering from endometriosis or human uterine cancer cells initiate a previously unknown cascade of signals that leads to cellular replication and further estrogen production, the paper says.

The ensuing cycle leads to abnormal growth of the cells lining the uterus, or endometrium, which occurs in endometriosis and uterine cancer, according to senior author Holly A. Ingraham, PhD, a professor in the UCSF School of Medicine’s Department of Cellular and Molecular Pharmacology.

“It turns out that displaced endometrial cells, such as those used in this study, are estrogen factories,” said Ingraham, who also is affiliated with the UCSF Helen Diller Family Comprehensive Cancer Center and the UCSF Center for Reproductive Sciences. “They pump out estrogen in a feed-forward pathway, so the more estrogen they produce, the more estrogen they’re capable of producing.”

While this pathway was previously unknown, Ingraham said a June 2009 paper led by researchers at the University of New Mexico and published in the journal “Nature Chemical Biology” showed that blocking the GPR30 receptor in this pathway decreases uterine proliferation in a mouse. The two together, she said, validate what researchers now think may be a key area in addressing both uterine cancer and endometriosis.

Uterine cancer is the fourth most common cancer in women, with more than 37,000 women being diagnosed each year in the United States alone, according to data from the Centers for Disease Control.

Endometriosis, in which endometrial cells grow in areas other than the uterus, is the most common gynecological disease and affects more than 5.5 million women in North America, according to the National Institutes of Health. The disease often causes severe pain and can lead to infertility.

Working in collaboration with clinicians at Northwestern University in Chicago, the UCSF team analyzed cells from women with ectopic endometriosis. By studying those patients’ endometrial cells, the team was able to identify an unusual, circular pathway involving these cells, the transmembrane estrogen receptor GPR30 and the nuclear receptor SF-1.

The researchers propose that this pathway increases local concentrations of estrogen and, together with classic estrogen-receptor signaling, control the proliferative effects of these estrogens in promoting endometriosis and endometrial cancers.

The UCSF team used a unique chemical biology approach, making use of a tamoxifen-like compound developed in the laboratory of co-author Thomas Scanlan, PhD, who is affiliated with both the UCSF Department of Pharmaceutical Chemistry and the Department of Chemical Biology at the Oregon Health Sciences University in Portland.

“Tamoxifen and other synthetic estrogens have been known to increase the risk of uterine cancer, but until now, we didn’t know why that was on a cellular level,” Ingraham said. “We think this pathway is going to be an important one in solving that mystery.”

The lead investigator on the paper was Benjamin C. Lin. Lin and co-author Sandra C. Tobias are affiliated with the Department of Pharmaceutical Chemistry at UCSF. Other co-authors are Miyuki Suzawa, in the UCSF Department of Cellular and Molecular Pharmacology; Raymond D. Blind in the UCSF Department of Pharmaceutical Chemistry and Department of Cellular and Molecular Pharmacology; and Serdar E. Bulun, in the Department of Obstetrics and Gynecology, Feinberg School of Medicine at Northwestern University.

The authors report no potential conflicts of interest in this research.

UCSF is a leading university dedicated to promoting health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care. For further information, visit http://www.ucsf.edu.

The addition of a chemotherapeutic drug for leukemia to a standard regimen of two other chemotherapy drugs appears to enhance the response of certain ovarian cancers to treatment, according to a pre-clinical study led by researchers in the Duke Comprehensive Cancer Center.

“We know that a pathway called SRC is involved in cell proliferation in certain types of cancers, including some ovarian cancers,” said Deanna Teoh, M.D., a fellow in gynecologic oncology at Duke and lead investigator on this study. “By examining gene expression data, we determined that the combination of the leukemia drug dasatinib (Sprycel) made carboplatin and paclitaxel more effective in cell lines with higher levels of SRC expression and SRC pathway deregulation.”

That synergistic effect, in which drugs used in combination strengthen each other’s efficacy, was absent when low SRC expression and low SRC pathway deregulation were present, Teoh said.

“These findings indicate that we may be able to direct the use of a targeted therapy like dasatinib based on gene expression pathways in select ovarian cancers,” she said.

The results of the study are being presented on a poster at the 100th annual American Association for Cancer Research meeting in Denver on April 19, 2009. The study was funded by the Prudent Fund and the National Institutes of Health.

“Our ultimate goal is to offer personalized therapy for women with ovarian cancer,” said Angeles Secord, M.D., a gynecologic oncologist at Duke and senior investigator on this study. “Hopefully in the future we will apply targeted therapies to individual patients and their cancers in order to augment response to treatment while minimizing toxic side effects.”

For this study, researchers examined four ovarian cancer cell lines, known as IGROV1, SKOV3, OVCAR3 and A2780. Three of the cell lines demonstrated high activation of SRC and one demonstrated lower SRC expression. All were treated in lab dishes with various combinations of the chemotherapeutic agents dasatinib, carboplatin and paclitaxel.

“We found that the addition of dasatinib to standard therapy in the three cell lines with significant SRC pathway deregulation IGROV1, OVCAR3 and A2780 enhanced the response of the cancer cells to therapy,” Teoh said. “Conversely, in SKOV3, which has minimal SRC protein expression and pathway deregulation, we saw the least amount of anti-cancer activity when we added dasatinib.”

It’s possible that by blocking the SRC activity with the dasatinib, we are enhancing the effect of the other chemotherapeutic agents, Teoh said.

The results of this study support the further investigation of targeted biologic therapy using a SRC inhibitor in some ovarian cancers, she said. Currently a phase I trial of a combination of dasatinib, paclitaxel and carboplatin is available for women with advanced or recurrent ovarian, tubal and peritoneal cancers.

Dasatinib is a chemotherapeutic that is currently FDA-approved for use in leukemia. It is manufactured by Bristol-Myers Squibb and is sold under the brand name Sprycel. Bristol-Myers Squibb provided the dasatinib used in this study.

Other researchers involved in this study include Tina Ayeni, Jennifer Rubatt, Regina Whitaker, Holly Dressman and Andrew Berchuck.

Duke University Medical Center

Cancer is a genetic disease. It occurs when changes take place in the genes that regulate cell division, cell growth, cell death, cell signalling and blood vessel formation either due to mutations caused by external factors such as smoking or radiation or due to inherited changes. This interaction between defective genes and environmental factors means that cancer is an extremely complex disease. Cancer of the uterus, or endometrial carcinoma, is no exception.

Cancer of the uterus is the commonest gynaecological malignancy in the West and accounts for between five and six per cent of all cancers in Swedish women. However, the symptoms are often vague, and we know little about the genetic factors that lead to the appearance and development of this form of cancer. It is therefore vital that these genes are identified, as this could enable doctors to make the diagnosis much more quickly and easily, allowing the development of more effective cancer treatment.

In her study, Sandra Karlsson, a researcher at the Department of Cell and Molecular Biology, has used inbred rats to locate the defective genes that cause uterine cancer. Like monozygotic (identical) twins, these inbred rats are genetically almost identical, which makes it much easier to study the influence of the environment in which they live.

“More than 90 per cent of the female rats in the study spontaneously developed uterine cancer. By using advanced techniques to analyse gene expression in the tumours, we succeeded in identifying a gene signature that could be used as a future diagnostic test for human uterine cancer,” says Sandra Karlsson.

The signature is made up of three genes. One of them protects the cell against oxygen free radicals. These free radicals are naturally and continuously produced in the cell, but excess amounts, which can damage the cell and the body’s DNA, are associated with over 200 diseases, from arteriosclerosis and dementia to rheumatism, cerebral haemorrhage and cancer. The studies carried out by Sandra Karlsson on human malignant tumours have confirmed that changes in this gene are present in early as well as late stage cancer.

“This shows that the identified gene has an important role in the origin and development of uterine cancer,” says Sandra Karlsson.

University of Gothenburg

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