When the DNA microarray study tells us that a large number of genes have been turned up (or turned down) by a disorder, the most likely explanation is that "

A major transcription factor is inactivated or an oncogene is overexpressed  

Explanation:

A microarray is a technique widely used in molecular biology for the detection of the expression of target genes. A microarray is composed of microscopic spots that contain DNA probes which hybridize with the target acid nucleic (generally an mRNA). The hybridization of probe-target produces fluorescence or chemiluminescence, thereby it is possible to detect gene expression in the sample. The inactivation of major transcription factors (e.g., p53) or overexpression of oncogenes (e.g., c-Myc) are well-known to produce aberrant gene expression patterns as observed in this case.

compost can be added to topsoil as a:

pesticide