Fetal bovine serum (fbs)

293T, MC57, MC57-HER2, SKBR3, and MC38-HER2 cell lines were cultured in Dulbecco’s Modified Eagle Medium (DMEM) supplemented with fetal bovine serum (10%; Bovogen Biologicals) and l-glutamine (2 mM; Gibco), incubated at 37°C, 10% CO₂. BW5147 cells were cultured in RPMI supplemented with fetal bovine serum (10%; Bovogen Biologicals) and l-glutamine (2 mM; Gibco), incubated at 37°C, 5% CO₂. Cell line identity was not independently verified by genetic testing. HER2 expression on tumor target and control cell lines was confirmed via anti-HER2 surface staining (BioLegend, Cat# 324412) and flow cytometry. All cell lines were regularly confirmed mycoplasma negative using the Stratagene Mycosensor PCR Assay Kit (Agilent, Cat# 302108).

All of the melanoma cell lines, except for D28 and A375, were sourced from Prof Nick Hayward’s lab at QIMR Berghofer as 2-dimensional cultures, then the 3-dimensional tumour sphere lines were derived from those. D28 cells were provided by Rick Pearson, Peter MacCallum Cancer Institute (Melbourne, Australia) and the A375 line was provided by Helen Rizzo, Westmead Institute for Cancer Research (Sydney, Australia). All 2-dimensional melanoma cell lines and primary human neonatal fibroblasts (NFF) were grown in RPMI1640 (Sigma Aldrich) supplemented 10% FBS (Bovogen), 2 mM L-Glutamine, 1 mM Sodium Pyruvate and 25 mM HEPES. All 3-dimensional melanoma tumour sphere cell lines were grown as described in^{17 (link)} without the addition of β-mercaptoethanol, in tissue culture flasks coated with 5 mg/ml Poly(2-hydroxyethyl methacrylate) (Sigma Aldrich). HeLa cells were grown in high glucose DMEM (Sigma Aldrich) supplemented with 10% FBS (Bovogen), 2 mM L-Glutamine, 1 mM Sodium Pyruvate and 25 mM HEPES. All cell lines were authenticated by STR profiling (Australian Genome Research Facility) and confirmed mycoplasma negative by the MycoAlert kit (Lonza).