miR-216b enhances the efficacy of vemurafenib by targeting Beclin-1, UVRAG and ATG5 in melanoma.

Autophagy maintains cells survival in many stressful conditions including starvation, growth factor deprivation and misfolded protein accumulation. Additionally, autophagic survival mechanisms are used by transformed tumor cells to inhibit cell death, limit drug effectiveness and possibly generate drug resistance. However, the mechanism of how cells utilize autophagy during drug resistance is not fully understood. Here, we demonstrate that miR-216b plays an important role in alleviating drug resistance by regulating autophagy in melanoma. We show that miR-216b attenuates autophagy by directly targeting three key autophagy genes Beclin-1, UVRAG and ATG5. Overexpression of these genes from miRNA immune cDNA constructs rescue autophagic activity in the presence of miR-216b. Antagomir-mediated inactivation of endogenous miR-216b led to an increase of Beclin-1, UVRAG, ATG5, and subsequent autophagic activity. More importantly, we have discovered that BRAF(V600E) inhibitor vemurafenib suppresses miR-216b activity, which in turn activates autophagy to generate drug resistance in both BRAFi-sensitive and -resistant cells. Strikingly, ectopic expression of miR-216b increases the efficacy of vemurafenib both in vitro and in vivo. Taken together, these data indicate that miR-216b regulates autophagy by suppressing three key autophagy genes, and enhances the antitumor activity of vemurafenib in BRAF(V600E) melanoma cells.

Luo M ，Wu L ，Zhang K ，Wang H ，Wu S ，O'Connell D ，Gao T ，Zhong H ，Yang Y ... -  《-》

Targeting signal-transducer-and-activator-of-transcription 3 sensitizes human cutaneous melanoma cells to BRAF inhibitor.

Wang X ，Qu H ，Dong Y ，Wang G ，Zhen Y ，Zhang L ... -  《-》

p53 Reactivation by PRIMA-1(Met) (APR-246) sensitises (V600E/K)BRAF melanoma to vemurafenib.

Intrinsic and acquired resistance of metastatic melanoma to (V600E/K)BRAF and/or MEK inhibitors, which is often caused by activation of the PI3K/AKT survival pathway, represents a major clinical challenge. Given that p53 is capable of antagonising PI3K/AKT activation we hypothesised that pharmacological restoration of p53 activity may increase the sensitivity of BRAF-mutant melanoma to MAPK-targeted therapy and eventually delay and/or prevent acquisition of drug resistance. To test this possibility we exposed a panel of vemurafenib-sensitive and resistant (innate and acquired) (V600E/K)BRAF melanomas to a (V600E/K)BRAF inhibitor (vemurafenib) alone or in combination with a direct p53 activator (PRIMA-1(Met)/APR-246). Strikingly, PRIMA-1(Met) synergised with vemurafenib to induce apoptosis and suppress proliferation of (V600E/K)BRAF melanoma cells in vitro and to inhibit tumour growth in vivo. Importantly, this drug combination decreased the viability of both vemurafenib-sensitive and resistant melanoma cells irrespectively of the TP53 status. Notably, p53 reactivation was invariably accompanied by PI3K/AKT pathway inhibition, the activity of which was found as a dominant resistance mechanism to BRAF inhibition in our lines. From all various combinatorial modalities tested, targeting the MAPK and PI3K signalling pathways through p53 reactivation or not, the PRIMA-1(Met)/vemurafenib combination was the most cytotoxic. We conclude that PRIMA-1(Met) through its ability to directly reactivate p53 regardless of the mechanism causing its deactivation, and thereby dampen PI3K signalling, sensitises (V600E/K)BRAF-positive melanoma to BRAF inhibitors.

Krayem M ，Journe F ，Wiedig M ，Morandini R ，Najem A ，Salès F ，van Kempen LC ，Sibille C ，Awada A ，Marine JC ，Ghanem G ... -  《-》

BRAF(V600) inhibition alters the microRNA cargo in the vesicular secretome of malignant melanoma cells.

Lunavat TR ，Cheng L ，Einarsdottir BO ，Olofsson Bagge R ，Veppil Muralidharan S ，Sharples RA ，Lässer C ，Gho YS ，Hill AF ，Nilsson JA ，Lötvall J ... -  《-》

Targeting ER stress-induced autophagy overcomes BRAF inhibitor resistance in melanoma.

Ma XH ，Piao SF ，Dey S ，McAfee Q ，Karakousis G ，Villanueva J ，Hart LS ，Levi S ，Hu J ，Zhang G ，Lazova R ，Klump V ，Pawelek JM ，Xu X ，Xu W ，Schuchter LM ，Davies MA ，Herlyn M ，Winkler J ，Koumenis C ，Amaravadi RK ... -  《-》