How would you use cDNA libraries to study the effect of a drug on gene expression in cancer cells?

Use restriction enzymes to cut mRNA from cancer cells, insert into vectors, sequence to identify changes in gene expression.

Treat cancer cells with the drug, isolate mRNA, create cDNA libraries, sequence to identify changes in gene expression.

Isolate genomic DNA from cancer cells, create genomic libraries, sequence to identify changes in gene expression.

Treat cancer cells with the drug, isolate proteins, create cDNA libraries, sequence to identify changes in gene expression.