Two Women with Metastatic Breast Cancer – Same Age, Same Disease, Two Very Different Functional Profiles

A day in the life of advanced breast cancer. Two different 37-year-old breast cancer patients, both mothers of young children, were seen in consultation on the same day.

The first had been referred by a colleague who was concerned that the patient’s ER positive breast cancer had disseminated to her brain despite aggressive standard chemotherapy. She was to undergo a craniotomy and a portion of fresh tumor would be submitted from the surgery to Rational Therapeutics for EVA-PCD functional profiling.

The second mother had metastatic triple negative breast cancer, which recurred after aggressive standard chemotherapy. She underwent neo-adjuvant treatment (preoperative) but at the time of her surgery, there was no evidence of response to the treatment. By the time we met her, only months into her diagnosis, new areas of metastatic disease were cropping up daily.

Microscope Detail2-lo resThe EVA-PCD assay results on these two “similar” patients were entirely different.

The results of the first patient with the ER positive tumor and brain metastases clearly identified treatments directed toward the PI3K pathway, with or without chemotherapy. We are recommending a combination of Everolimus plus chemotherapy.

The second patient had a completely different profile. Indeed, the degree of drug resistance was quite striking. A three-drug combination was among the most active from almost two dozen drugs tested.  The other option appeared to be a new class of drugs called the cyclin dependent kinase (CDK) inhibitors.

On a functional level, we used targeted drugs to probe for sensitivity to inhibitors of these cancer signal pathways. Unlike genomic profiles that tell you whether the gene is present or absent, we can tell whether the gene is driving the tumor. Functional profiling.

One patient is now under my care and the other will begin treatment under the care of a colleague in Orange County, CA. We will await results of these assay-directed therapies and wish these two young patients every success.

Triple Negative Breast Cancer: Worse or Just Different?

The term “triple negative breast cancer” (TNBC) is applied to a subtype of breast cancers that do not express the estrogen or progesterone receptors. Nor do they overexpress the HER2 gene. This disease constitutes 15 – 20 percent of all breast cancers and has a predisposition for younger women, particularly those of black and Hispanic origin. This disease may becoming more common; although, this could reflect the greater awareness and recognition of this disease as a distinct biological entity.

On molecular profiling, TNBC has distinct features on heat maps. The usual hormone response elements are deficient, while a number of proliferation markers are upregulated.  Not surprisingly, this disease does not respond to the usual forms of therapy like Tamoxifen and the other selective estrogen response modifiers known as SERMs. Nonetheless, TNBC can be quite sensitive to cytotoxic chemotherapy. Indeed, the responsiveness to chemotherapy can provide these patients with complete remissions. Unfortunately, the disease can recur. Complete remission maintained over the first three to five years is associated with a favorable prognosis, with recurrence rates diminishing over time and late recurrences more often seen in estrogen receptor-positive cancers.

Triple negative breast cancer is not one, but many diseases.

MTOR-pathway-ger Among the subtypes are those that respond to metabolic inhibitors such as the PI3K and mTOR directed drugs. Another subset may respond to drugs that target epidermal growth factor. There are basal-types that may be somewhat more refractory to therapy, while a subset may have biology related to the BRCA mutants, characterized by DNA repair deficiencies and exquisite sensitivity to Cisplatin-based therapies. Finally, a last group is associated with androgen signaling and may respond to drugs that target the androgen receptor.

Some years ago, we used the EVA-PCD platform to study refractory patients with breast cancer and identified exquisite sensitivity to the combination of Cisplatin plus Gemcitabine in this patient group. We published our observations in the Journal of Clinical Oncology and the combination of Cisplatin or Carboplatin plus Gemcitabine has become an established part of the armamentarium in these patients.

The I-SPY-2 trial has now used genomic analyses confirming our observations for the role of platins in TNBC. This iSignal_transduction_pathways.svgn part reflects the DNA repair deficiency subtype associated with the BRCA-like biology. More recently, we have examined TNBC patients for their sensitivity to novel therapeutic interventions. Among them, the PI3K and mTOR inhibitors, as well as the glucose metabolism pathway inhibitors like Metformin. Additional classes of drugs that are revealing activity are the cyclin-dependent kinase inhibitors, some of which are moving forward through clinical trials.

One feature of triple negative breast cancer is avid uptake on PET scan. This reflects, in part, the proliferation rate of these tumors, but may also reflect metabolic changes associated with altered glucose metabolism. In this regard, the use of drugs that change mitochondrial function may be particularly active. Metformin, a member of the biguanide family influences mitochondrial metabolism at the level of AMP kinase. The activity of Metformin and related classes of drugs in triple negative breast cancer is a fertile area of investigation that we and others are pursuing.

When we examine the good response of many triple negative breast cancers to appropriately selected therapies, the potential for durable complete remissions and the distinctly different biology that TNBC represents, the question arises whether TNBC is actually a worse diagnosis, or simply a different entity that requires different thinking. We have been very impressed by the good outcome of some of our triple negative breast cancer patients and believe this a very fertile area for additional investigation

Using Function to Inform Genomics

Recently, I was asked to evaluate a charming young woman with an unusual gynecologic primary. She had received numerous forms of therapy and surgery for her low-grade carcinoma. Her most recent surgery provided tissue to our laboratory for analysis. The results were consistent with the clinical presentation, revealing relative resistance to virtually all conventional chemotherapeutic drugs, but a very striking pattern of sensitivity to three compounds associated with the insulin like growth factor signaling pathway.

As all three compounds pointed to activity in this pathway, I reasoned that the patient had a mutation upstream, as I wrote in my report to her physician. I suggested that they should investigate this pathway.

I was subsequently apprised that, upon my recommendation and at the request of patient’s husband, an analysis had been submitted to a laboratory that identified a mutation in PI3K, the very pathway that I had identified in our functional analysis. Thus, this patient’s resistance to chemotherapeutics and sensitivity to PI3K inhibitors reflected the profound survival signal provided by this mutation. Of interest, when the family originally requested a molecular profile be conducted in parallel with our functional profile, the commercial lab in Arizona did not include PI3K mutational studies. It wasn’t until the functional results pointed to the PI3K pathway that the specific mutational analysis was undertaken and found positive.

This experience is very similar to our original work with the EGFR inhibitors gefitinib and erlotinib. Several years before the EGFR mutation was identified and long before the mutational analysis was commercially available we identified activity in patients using the functional platform. Patients were then treated based upon the EVA-PCD results under protocol with every one of these patients responding, as we reported (Nagourney Proc ASCO, 2007). This speaks to the robustness of the functional platform and to its capacity to guide drug development.

American Association of Cancer Research (AACR) Meeting 2011

The Sunday, April 3, 2011, experimental and molecular therapeutics session at the AACR 102nd annual meeting included our presentation on signal transduction inhibitors. Using MEK/ERK and PI3K-MTOR inhibitors we explored the activities, synergies and possible clinical utilities of these novel compounds.

The findings were instructive. First, we saw a good signal for both compounds utilizing the Ex-vivo Analysis of Programmed Cell Death (EVA-PCD) platform. Second, we saw disease-specific activity for both compounds. For the MEK/ERK inhibitor, melanoma appeared to be a favored clinical target. This is highly consistent with our expectation. After all, many melanomas carry mutations in the BRAF gene, and BRAF signals downstream to MEK/ERK. By blocking MEK/ERK, it appeared that we blocked a pathway fundamental to melanoma progression. Indeed, MEK/ERK inhibitors are currently under investigation for melanoma.

For PI3K inhibitors, the highest activity was observed in uterine cancers. This is interest, because uterine carcinomas are often associated with a mutation in the PTEN gene. PTEN is a phosphatase tumor suppressor that functions to block activation of the PI3K pathway. Thus, mutations in the tumor suppressor unleash PI3K signaling, driving tumors to grow and metastasize. Blocking PI3K provided a strong signal, indicating that this approach may be very active in tumors associated with these oncogenic events.

The third point of interest in our report was, perhaps, its most important. Specifically, that we can explore those diseases where MEK-ERK, PI3K and mTOR signaling are less established targets. Cancers of the lung, ovary, colon or breast all manifested profiles of interest. When we combined both pathway inhibitors in a process we call horizontal inhibition, renal cell carcinoma popped up as the best target. These results, though exploratory, suggest a superior approach for drug development, allowing us to identify important leads much faster than the clinical trial process.