Gene expression assay for measurement of DNA mismatch repair deficiency

1. A method of treating cancer in a subject identified as having a mismatch repair deficiency, wherein the cancer is selected from a colon cancer, an esophageal cancer, a stomach cancer, and a uterine cancer,

the method including administering to the subject identified as having mismatch repair deficiency at least one treatment comprising an immunotherapy,

and wherein the subject is identified as having mismatch repair deficiency by a method comprising:

a) measuring the gene expression level of at least one gene selected from MLH1, MSH2, MSH6 or PMS2 in a tumor sample from the subject, wherein measuring comprises an enzyme free method;

b) determining for each of the at least one gene a score Z, wherein Z=(x−μ 1 )/σ 1 , wherein x is the log-transformed normalized expression of the at least one gene, μ 1 is the mean of the log-transformed normalized expression of the at least one gene in non-hypermutated samples, and σ 1 is the standard deviation of the log-transformed normalized expression of the at least one gene in non-hypermutated samples;

c) determining a score MLS, wherein MLS=(Z m +c 1 )/c 2 , wherein Z m is the minimum Z score of the at least one gene, and wherein

c 1 is 0 and c 2 is 1 when one gene is used,

c 1 is 0.56 and c 2 is 0.83 when two genes are used,

c 1 is 0.85 and c 2 is 0.75 when three gene are used, or

c 1 is 1.03 and c 2 is 0.70 when four genes are used;

d) comparing the MLS score with a predetermined cutoff value, wherein the cutoff value identifies mismatch repair deficiency in a subject with at least 95% specificity; and

e) identifying the presence of mismatch repair deficiency in the subject when the MLS score is equal to or greater than the predetermined cutoff value.

2. The method of claim 1 , wherein the cutoff value identifies mismatch repair deficiency in a subject with at least 99% specificity.

3. The method of claim 1 , wherein the cutoff value is 1.645.

4. The method of claim 1 , wherein the cutoff value is 2.326.

5. The method of claim 1 , wherein the cutoff value is 2.576.

6. The method of claim 1 , wherein the at least one gene is MLH1.

7. The method of claim 1 , wherein the at least one gene includes each of MLH1, MSH2, MSH6 and PMS2.

8. The method of claim 1 , wherein the treatment comprises administering to the subject a checkpoint inhibitor therapy.

9. The method of claim 1 , wherein the treatment comprises administering to the subject pembrolizumab, nivolumab, atezolizumab, avelumab, durvalumab or a combination thereof.

10. The method of claim 1 , wherein the treatment comprises administering to the subject pidilizumab, REGN2810, AMP-224, MEDI0680, PDR001, CT-001 or a combination thereof.

11. The method of claim 1 , wherein the treatment comprises administering to the subject a CTLA4 antibody.

12. The method of claim 11 , wherein the CTLA4 antibody comprises ipilimumab, tremelimumab or a combination thereof.