Tuberous sclerosis complex (
TSC)
tumors are presently incurable despite a
cytostatic response to mTOR pathway inhibition because recurrence of disease occurs
after treatment is discontinued. Here, we explored the hypothesis that inhibiting
tyrosine kinase activity in mesenchymal lineage-specific
platelet-derived growth factor receptor β (PDGFRβ) signaling in
TSC tumors is cytocidal and attenuates
tumorigenesis at significantly higher levels than treatment with an mTOR inhibitor.
Rapamycin-induced versus
tyrosine kinase inhibitor (TKI)-induced renal
angiomyolipoma (AML) and pulmonary
lymphangioleiomyomatosis (
LAM)
tumor cells were comparatively analyzed using cell survival assays,
RNA sequencing, and bioinformatics to distinguish tumoricidal mechanisms adopted by each
drug type. The efficacy of
imatinib therapy was validated against spontaneously developing renal
cystadenomas in
tuberous sclerosis Tsc2+/- mouse models (C57BL/6J mice; N = 6; 400 mg/kg/d; oral gavage) compared with Tsc2+/- mice treated with PBS (C57BL/6J mice; N = 6). Our study revealed that TKIs
imatinib and
nilotinib were cytocidal to both pulmonary
LAM and renal AML cell cultures through the downregulation of the
glycoprotein GPVI pathway and resultant disruption in mitochondrial permeability, increased cytosolic
cytochrome C, and
caspase 3 activation. Importantly, renal
tumor growth was significantly attenuated in
imatinib-treated Tsc2+/- mice compared with PBS treatment. The preclinical studies reported here provide evidence documenting the effectiveness of TKIs in limiting
LAM and AML cell growth and viability with important clinical potential. Furthermore, these drugs elicit their effects by targeting a PDGF pathway-dependent apoptotic mechanism supporting the investigation of these drugs as a novel class of
TSC therapeutics.