Table 2.

Preclinical studies exploring the role of PI3K, AKT and/or mTOR inhibitors radiosensitising SCC and NSCLC.

Author	Year	Type of Cancer	Experimental Model	Drug (s) Tested	Drug Category	Radiotherapy Dose	Summary Outcome
Assad et al. [79]	2018	Cervical SCC	In vitro: (cell line): HeLa	Temsirolimus, everolimus, resveratrol, curcumin, epigallocatechin gallate	mTOR inhibitors	2 Gy	Radiosensitisation observed with mTOR inhibitors through late apoptosis and necrosis
Yu et al. [37]	2017	Head and Neck (Oral) SCC	In vitro (cell lines): OML1, OML1-R, SCC4, SCC25, Patient derived cell lines In vivo: (xenograft) OML1-R + mice	NVP-BEZ235 Everolimus AZD2014 BKM120	PI3K and mTOR inhibitor mTOR inhibitorm TOR inhibitor PI3K inhibitor	10 Gy or 0–4 Gy (variable)	Dual inhibition of PI3K and mTOR performed significantly better by inhibiting cell proliferation BEZ235 + radiotherapy reduced cell viability 2.4–6.3-fold Radiotherapy with BEZ235 significantly suppressed the growth of xenograft tumours (p =0.00017)
Leiker et al. [75]	2015	Head and Neck SCC	In vitro (cell lines): UMSCC1-wtP53, UMSCC46-mtP53, normal human fibroblast line (1522) In vivo (xenograft): UMSCC1 + mice	PF-05212384	PI3K and mTOR inhibitor	Variable range (0 to 8 Gy)	Enhanced radiosensitisation demonstrated in vitro and in vivo after treatment Compared to normal human fibroblasts tumour cells more effectively radiosensitised.
Liu et al. [73]	2015	Head and Neck (Naso-pharyngeal) SCC	In vitro (cell lines): CNE-2, 5-8F, 6-10B, CNE-1, NP69 In vivo (xenograft): 5-8F + mice	GSK2126458 PKI-587	PI3K and mTOR inhibitor PI3K and mTOR inhibitor	4 Gy	Both drugs: Increased DNA damage and G2–M cell cycle delay Induced apoptosis and inhibited cell proliferation Significantly inhibited xenograft tumour growth and proliferation Suppressed phosphorylation of mTOR, AKT and 4E-BP1
Cerniglia et al. [74]	2012	Head and Neck SCC	In vitro (cell line): SQ20B In vivo: (xenograft) SQ20B + mice	NVP-BEZ235	PI3K and mTOR inhibitor	Variable range (0 to 6 Gy)	Knockdown of pathway components AKT, p110- α, or mTOR led to radiosensitisation, but not to the same extent as NVPBEZ235 Loss of resolution of H2A histone family member X foci (γ-H2AX) Induced autophagy in cell lines and xenograft tumours
Fokas et al. (1) [77]	2012	Head and Neck (laryngeal and hypo -pharyngeal) SCC	In vitro (cell lines): SQ20B, FaDu	NVP-BGT226 NVP-BEZ235	PI3K and mTOR inhibitor PI3K and mTOR inhibitor	6 Gy	Both inhibitors can enhance radiation-induced killing of tumour cellsBoth inhibited phosphorylation of AKT, mTOR and led to DNA damage persistence (increased γ-H2AX foci) G2 cell cycle delay
Bozec et al. [78]	2011	Head and Neck SCC	In vivo (xenograft): CAL33 + mice	Temsirolimus (+ cetuximab and bevacizumab)	mTOR inhibitor Cytotoxic chemotherapy + VEGF inhibitor	6 Gy three times a week	Longest delay in tumour growth observed when temsirolimus combined with cetuximab, bevacizumab and radiotherapy (p-0.01) Reduced Ki-67 and BCL2 implying decreased tumour proliferation as well as anti-apoptotic effects
Fokas et al. (2) [76]	2011	Head and Neck SCC	In vitro (cell line): FaDU HRE-Luc In vivo (xenograft): FaDU HRE-Luc + mice	NVP-BEZ235BKM120	PI3K and mTOR inhibitor PI3K inhibitor	6 Gy	Dual inhibitor modulated the tumour microenvironment Radiosensitised tumours by prolonging the time taken for normalisation of tumour vasculature
Prevo et al. [23]	2008	Head and Neck SCC	In vitro (cell line): SQ20B	PI-103	PI3K, mTOR and DNA-PK inhibitor	Variable range (0–6 Gy)	Reduced AKT phosphorylation. Persistent DNA damage after treatment (increased γ-H2AX foci). G2/M phase delay. Overall effects led to reduced cell survival.
Holler et al. [39]	2016	NSCLC	In vitro (cell lines): H661, H460, SK-MES-1, HTB-182, A549	Rapamycin MK-2206	mTOR inhibitor AKT inhibitor	Variable range (0–5 Gy)	AKT inhibition led to rapamycin induced radiosensitisation in radio-resistant NSCLC cells Dual inhibition of AKT and mTOR significantly inhibited DNA DSB repair compared to single inhibition
Toulany et al. [38]	2016	NSCLC		PI-103 PD98059	PI3K, mTOR and DNA-PK inhibitor MEK inhibitor	4 Gy	Decreased DNA DSB repair by inhibited DNAP-PKcs activity short term Combining MEK inhibitor prevented indirect activation of AKT (RAS/RAF/MEK pathway). This led to more prolonged and greater radiosensitisation effects
Kim et al. (1) [80]	2014	NSCLC	In vitro (cell line): H460-Luc2 (cisplatin resistant clone) In vivo (xenograft): H460-Luc2 (cisplatin resistant clone) + mice	NVP-BEZ 235	PI3K and mTOR inhibitor	Variable range (0–6Gy)	BEZ-235 enhanced radiosensitivity (p-0.01) Increased autophagy and cell proliferation Significant tumour growth delay observed in treated xenografts Reduced caspase-3 activity, cell proliferation and vascular density
Kim et al. (3) [81]	2013	NSCLC	In vitro (cell lines): H1650, HCC827	Everolimus	mTOR inhibitor	Variable range (0–3Gy)	Enhanced autophagy following mTOR inhibition and radiotherapy Radioresistance observed in HCC827 cell lines
Mauceri et al. [82]	2012	NSCLC	In vitro (cell line): A549 In vivo (xenograft): A549 + mice	Everolimus	mTOR inhibitor	5 × 6 Gy	Everolimus altered gene expression in treated cells Everolimus with radiotherapy significantly slowed tumour growth compared to radiotherapy alone in xenograft (p = 0015).
Konstantinidou et al. [36]	2009	NSCLC	In vitro (cell lines): H23, H460, H2122 In vitro (mouse cell lines): LKR10, LKR13 In vivo (xenograft): H460 + mice	NVP-BEZ235 LY294002 + rapamycin	PI3K and mTOR inhibitor PI3K and PI3K-like kinase inhibitor + mTOR inhibitor	Variable range (1–6 Gy)	Anti-proliferative effects, G1 growth arrest and overall radiosensitisation observed in all treated cell lines and xenografts NVP-BEZ 235 or LY294002 + rapamycin demonstrated comparable radiosensitising effects
Kim et al. (2) [83]	2008	NSCLC	In vitro (cell line): H460 In vivo (xenograft): H460 + mice	Everolimus Z-DEVD	mTOR inhibitor Caspase -3 inhibitor	Variable (0–6Gy)	The combination of Z-DEVD and RAD001 more potently radiosensitised H460 cells than individual treatment alone. Increased radiosensitisation predominantly through enhanced autophagy