New Generation Testing Methods for Superior Accuracy

Dr. Weisenthal invented what has been called the "gold standard" method for testing the ability of a chemotherapy drug or combination of drugs to kill  cancer cells as they exist uniquely in the body of each cancer patient.  His pioneering work and 35 years of dedication to the concept of measuring cancer cell killing spawned an entire new generation of chemosensitivity tests. All Weisenthal Cancer Groups testing methods measure cancer cell death.  Dr. Weisenthal's methods must not be mistaken for less accurate testing methods that measure what is called "inhibition of cell proliferation."  We do NOT use this method.  The distinction is extremely important.  

Unfortunately, many physicians are not aware of the distinction between the two types of testing. Many physicians are familiar only with largely abandoned methods called the Clonogenic Assay, the Capillary Cloning Assay, the Thymidine Incorporation Assay, and the Oncotech EDR Assay.  Physicians and patients are justified in being wary of those older tests.  Those older tests were not bad, necessarily, but there were both theoretical and practical concerns that limited their reliability and utility.  

Here is another important disctinction between Dr. Weisenthal's approach and that of other labs:  Most labs use only one testing method.  Dr. Weisenthal’s lab has the capability to perform five different cell death testing methods.  For each patient, we apply at least three of these methods.  Why so many?  It is because each technology measures different processes occurring within the cell.  Depending upon the condition of the specimen we receive and the anti-cancer drugs we are testing against your tumor cells, some tests are better suited than others. 

You have read elsewhere on this website that cancer is not a one-size-fits-all disease.  Dr. Weisenthal believes this principle also applies to the testing process itself and so he designs a testing strategy for you alone.  He does this by applying testing methods and selecting candidate drugs that are most appropriate specifically for you, depending upon a variety of factors.  Dr. Weisenthal’s unique and highly comprehensive personalized testing approach provides you several benefits:

- It increases the accuracy and utility of the information Dr. Weisenthal is able to obtain for you.


- In the case of low cancer cell yield from a suboptimal specimen it can enable Dr. Weisenthal to test the drugs that are most important for you, based upon your very specific medical history.


- It enhances the accuracy and predictive utility of your test results by allowing for comparative analysis of results obtained from different but highly complementary assays.


- It ensures that each chemotherapy drug under consideration for you is assessed in the specific assay system that is most appropriate for that drug, based upon the way each drug works against cancer cells (the mechanism of anti-cancer activity varies widely from one drug to the next).  This is extremely important and no other lab does it this way.


Something else Dr. Weisenthal does that many other labs do not is to test each anti-cancer drug at two different concentrations.  This is NOT intended to suggest how much of the drug you should eventually receive.  Rather, this is done to enhance test accuracy and to better assess each drug’s effectiveness at killing your cancer cells. 

And so we test each of the 20 to 30 or more chemotherapy drugs and drug combinations for you in three different assay systems and at two different drug concentrations.  Add to this the necessary positive and negative assay control drugs we also test for you and it means we actually are performing over 120 individual cell profiling tests on your behalf. 

Compare this to most other labs that test 7 to 10 drugs in only one assay system and at only one drug concentration.  Dr. Weisenthal’s methods require a lot more work and, frankly, they do add considerable expense for us and for you.  But we know from experience that it pays huge dividends for you in the form of more extensive and more accurate information to help in designing your treatments.  

When it comes to providing you and your physician with potentially life-saving treatment data Dr. Weisenthal does not take shortcuts.

For highest predictive accuracy patient specimens received at our laboratory are tested in parallel using multiple, complimentary assay technologies.  In most cases, three or more of the following assay technologies are applied for each patient.  

DISC ASSAY (Differential Staining Cytotoxicity)

This assay was originated by Dr. Weisenthal while he was a Clinical Associate at the National Cancer Institute.  In the test the entire contents of a  culture of cancer cells are cytocentrifuged onto permanent microscope slides after being exposed to vatrious anti-cancer drugs.  The cells are differentially stained to allow discrimination of normal versus neoplastic cells and living versus dead cells.

The endpoint for cell death in this test is delayed loss of membrane integrity.  This is recognised as a surrogate for apoptosis. Apoptosis is the means by which most chemotherapy drugs are known to work.

Advantages of the DISC assay include direct visualization of tumor cells and establishment of a permanent archival record. 

The DISC assay was the first of the new-generation functional tumor cell profiling methods to feature the cell death endpoint, upon which nearly all new-generation functional profiling assays subsequently were based. 

Interpretation of DISC assay slides is highly labor-intensive but the assay is widely-regarded among experts in the field to be the gold standard owing to the ability to examine directly each cell in order to positively discriminate tumor cells from non-tumor cells and to better characterize drug effects upon the entire tumor cell population. 

Click here to see a simplified graphic DISC assay methodology flowchart. 


MTT Assay [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide]

The MTT assay measures mitochondrial metabolism in the entire cell culture. In the assay, yellow tetrazolium salt (MTT) is reduced in metabolically active cells to form purple formazan.  The color can then be quantified by spectrophotometry, enabling an accurate measurement of metabolic activity.


ATP (Adenosine Triphosphate)

This test measures cellular ATP content by luminometry, based on the luciferin/luciferase reaction. Cells maintain a critical ATP thresholds whose measurement reflects cell viability, specifically indicating, in functional tumor cell profiling, whether apoptotic cell death has occurred during drug exposure.


Redox Assay (resazurin) assay measures total metabolic activity in the entire cell culture, using the Alamar Blue reagent. 


Caspase 3/7 assay measures the activation of caspases 3 and 7 using luminometry.


All of the above testing methods utilize the cell death, apoptotic assay endpoint.  This approach was pioneered by Dr. Weisenthal and is now the preferred method used in labs worldwide.