Activation of MAPK signalling results in resistance to saracatinib (AZD0530) in ovarian cancer

Abstract

SRC tyrosine kinase is frequently overexpressed and activated in late-stage, poor prognosis ovarian tumours, and preclinical studies have supported the use of targeted SRC inhibitors in the treatment of this disease. The SAPPROC trial investigated the addition of the SRC inhibitor saracatinib (AZD0530) to weekly paclitaxel for the treatment of platinum resistant ovarian cancer; however, this drug combination did not provide any benefit to progression free survival (PFS) of women with platinum resistant disease. In this study we aimed to identify mechanisms of resistance to SRC inhibitors in ovarian cancer cells. Using two complementary strategies; a targeted tumour suppressor gene siRNA screen, and a phospho-receptor tyrosine kinase array, we demonstrate that activation of MAPK signalling, via a reduction in NF1 (neurofibromin) expression or overexpression of HER2 and the insulin receptor, can drive resistance to AZD0530. Knockdown of NF1 in two ovarian cancer cell lines resulted in resistance to AZD0530, and was accompanied with activated MEK and ERK signalling. We also show that silencing of HER2 and the insulin receptor can partially resensitize AZD0530 resistant cells, which was associated with decreased phosphorylation of MEK and ERK. Furthermore, we demonstrate a synergistic effect of combining SRC and MEK inhibitors in both AZD0530 sensitive and resistant cells, and that MEK inhibition is sufficient to completely resensitize AZD0530 resistant cells. This work provides a preclinical rationale for the combination of SRC and MEK inhibitors in the treatment of ovarian cancer, and also highlights the need for biomarker driven patient selection for clinical trials.

IGF2BP1 is a targetable SRC/MAPK-dependent driver of invasive growth in ovarian cancer

“…This was validated IGF2BP1-dependent for the impairment of 3D growth and invasion in cellulo and the peritoneal spread of tumour cells in experimental mouse tumour models. In support of this, previous studies report a substantial therapeutic benefit of combined inhibition of MAPK/SRC signalling in EOC tumour models [8,16]. Thus, our findings suggest IGF2BP1 as a novel marker for EOC therapy.…”

“…In EOC xenograft models, their coapplication proved beneficial over single drug therapies, since MEK inhibition re-sensitized saracatinib resistant cells [8,16]. These findings provide preclinical evidence suggesting that the combination of SRC and MEK inhibitors is beneficial in the treatment of ovarian cancer and highlights the need for identifying biomarkers for selecting patients for clinical trials [8].…”

“…However, activation of the MAPK pathway is associated with resistance to saracatinib. MEK inhibition by selumetinib proved effective in resensitizing saracatinib resistant cells [8]. Co-activation of SRC and MAPK was reported in HGSOC patients and combined SRCi/MEKi impaired tumour growth in vivo more effectively than monotherapies [16].…”

“…This provides a rationale for their sensitivity towards platinum therapies and the potential use of poly(ADPribose) polymerase (PARP) inhibitors [1,6,7]. Although promising initially, PARP-and SRC-directed therapies suffer from occurring resistances and the lack of biomarkers required to identify patients benefitting from the respective treatments [8][9][10][11].…”

“…Accordingly, small molecule inhibitors of SRC and ERK1/ 2-activating MEK, in particular saracatinib and selumetinib, are tested individually in clinical trials (ClinicalTrials.gov Identifiers: NCT01196741; NCT00610714; NCT00551070; NCT03162627) [11,22]. In EOC xenograft models, their coapplication proved beneficial over single drug therapies, since MEK inhibition re-sensitized saracatinib resistant cells [8,16]. These findings provide preclinical evidence suggesting that the combination of SRC and MEK inhibitors is beneficial in the treatment of ovarian cancer and highlights the need for identifying biomarkers for selecting patients for clinical trials [8].…”