At the Breast Cancer Symposium 2009

[Jackie07]

Remember the Human Genome project? The attempt to map all the genes in the human body had a slow start. The traditional steps taken by the government agencies - with the best brain and top scientists - was so slow that Craig Venter finally took off and formed his own company to 'speed things up'. And he succeeded - several years before the predicted time.

Hopefully the current debate will continue and help speed things up...

[gdpawel]

They may have to wait awhile longer.

http://her2support.org/vbulletin/showthread.php?t=46200

[gdpawel]

There are any number of variables that affect drugs. These include the rate of excretion of the drugs by the kidneys and liver, protein binding and a myriad of other biological factors.

Some anticancer drugs are actually pro-drugs: they need to be first activated in the liver before becoming biologically active. So in vitro testing must administer the active forms of these agents, not the pro-drug form that is given to patients.

In the body, these cells interact with and supported by other living cells, both malignant and non-malignant cells. That is why cell-death functional profiling assays study cancer cells in small clusters, or microspheroids.

Analysis of these microspheroids provides a snapshot of cancer's behavior within the human body and provides a more accurate representation of how cancer cells are likely to respond to treatment in the clinic.

It is crucial that there is no manipulation of isolated cancer cells to make them grow, which was an important point of distinction with earlier cell-growth assays.

Drs. Larry Weisenthal and Robert Nagourney adopted this concept and began applying the term microclusters.

Real-life cancers grow as a complex organism that includes both malignant and non-malignant components. It may include fibrous tissue, mesothelial cells, fibroblasts, endothelial cells, etc.

In order to exhibit its most characteristic behavior patterns, a cancer cell needs to be surrounded by a colony of other cells, both normal and malignant.

Human tumors represent micro-ecosystems composed of transformed cells, stroma, fibroblasts, vascular elements, extra-cellular protein matrices and inflammatory elements.

The behavior of human cancers and their reponse to therapy reflect the complex interplay between humoral, vascular, adhesion and cytokine-mediated events acting in concert.

Tumors are very complex organisms. Ignoring this complexity, most studies of human cancer in culture have focused upon individual tumor cells that have been removed from their complex microenvironoment.

Cells are routinely broken up by mechanical and enzymatic means, which alters their subsequent behavior. Some previous methods of assays limited their analysis only to isolated tumor cells and failed to incorporate the crucial contribution of non-tumorous elements to the cancer phenomenon.

When allowed to grow in vitro, living cancer cells develop into these tiny micro-spheroid clusters that form a complex biosystem in which each malignant cell reacts upon its fellow colonists in subtle but important ways.

Each of these microspheres contains all the complex elements of tumor biosytems that are found in the human body and which can impact clinical reponse.

Source: Nagourney RA, Kollin CA, Sommers B, Su Y-Z, Evans SS. Functional profiling of human tumors in primary culture: a platform for drug discovery and therapy selection, AACR abstract #1546, 2008

[gdpawel]

As our understanding of breast cancer biology continues to advance, this disease has come to be understood as many different diseases. Original categorizations based on histology lead to lobular versus ductal subtypes. Thereafter, recognition of estrogen and progesterone status, and finally HER2 status provided further subcategorizations.

Over the past decade, molecular subtypes have characterized this disease into a series of signatures characterized by luminal, basal and other groupings with distinct prognoses. Within the context of these categories, the triple negative breast cancers have emerged as an important target.

These patients whose tumors do not mark for estrogen, progesterone, or HER2 on immunohistochemical or FISH analyses, appear to carry features that segregate them into a BRCA1-like biology. This is of great interest clinically for it offers the opportunity to treat these patients with drugs found active in the BRCA mutant populations.

Among the most active drugs in these patients are the PARP inhibitors. The excellent results with PARP inhibitors and BRCA mutants have been followed by striking response and survival data combining PARP inhibitors with carbo-platinum and gemcitabine. PARP inhibitors by inhibiting DNA damage response can enhance the effects of ionizing radiation, mustard alkylators, topoisomerase inhibitors, platins, and intercalating agents.

We have explored the biology of PARP inhibitors in breast and other cancers. In these investigations, our lab to applies the functional profiling platform to understand how PARP inhibitors enhance the effects of drugs and drug combinations.

To date, we have observed good activity for the PARP inhibitors as single agents in BRCA1 positive patients, and in some triple negative patients. More interesting, will be the results combining the PARP inhibitors with mustard alkylators, platins, and drug combinations to optimize PARP inhibitor combinations.

This work is ongoing in triple negative and BRCA positive patients as well as other tumor types where the PARP inhibitors may prove useful in the future.

[Dr. Nagourney is medical and laboratory director at Rational Therapeutics, Inc., in Long Beach, California, and an instructor of Pharmacology at the University of California, Irvine School of Medicine. He is board-certified in Internal Medicine, Medical Oncology and Hematology.]