Our results showed that PD-L1 was frequently expressed in functioning PAs with association of aggressive behaviors in PAs. The immunotherapy could be a promising treatment option of PAs.

Invasive pituitary adenomas (PAs) are often refractory to standard therapy and salvage treatment with temozolomide (TMZ). Hyperactivation of the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway contributes to chemotherapy resistance in many cancers. XL765, a novel dual-PI3K/mTOR inhibitor, has recently shown its efficacy as a monotherapy and in combination with conventional therapeutics in many cancers. The hyperactive PI3K/AKT/mTOR pathway frequently occurs in invasive PAs. In this study, we investigated whether XL765 sensitizes PA cells to TMZ in vitro and in vivo. Experiments were carried out to evaluate the effect of XL765 and TMZ alone or in combination on cell proliferation and apoptosis of PA cell lines (αT3-1, GH3, and MMQ) in vitro as well as the tumor growth and serum GH and prolactin secretions in a GH3 xenograft tumor model of female nude mice. XL765 and TMZ synergistically inhibited the growth of PA cell lines and induced apoptosis. Combination of XL765 and TMZ synergistically inhibited tumor growth, decreased serum GH and prolactin levels, and reduced the sacrifice rate of GH3 xenograft tumor models without increased systemic side effects. In addition, XL765 in combination with TMZ dramatically decreased phosphorylation of AKT and mTOR as well as the expression of Bcl-2. The increased expression of cleaved poly (ADP-ribose) polymerase and Bcl-2-associated X protein along with elevated caspase-3/7 activity were also observed in the combination group. Therefore, dual inhibitors of PI3K and mTOR may enhance alkylating agent-mediated cytotoxicity and provide a novel regimen in the treatment of invasive PAs.

Invasive pituitary adenomas (PAs) are generally refractory to conventional therapy and salvage treatment with temozolomide (TMZ). In addition to antiprotozoan effects, pyrimethamine (PYR) has recently shown its strong antitumor activity as an antineoplastic agent or in combination with TMZ in metastatic melanoma cells. In this study, the effects of TMZ, PYR or TMZ/PYR combination on rat/mouse PA cell lines aT3-1, GH3, MMQ and ATt-20 as well as GH3 xenograft tumor model were evaluated. TMZ/PYR combination synergistically inhibited proliferation, invasion and induced apoptosis of these PA cell lines in vitro. Strikingly, combination treatment with TMZ and PYR produced synergistic antitumor activity and enhanced the survival rate of GH3 xenograft tumor models without increasing systemic side effects. In addition, TMZ/PYR induced cell cycle arrest, increased DNA damage, upregulated the expression of cathepsin B, BAX, cleaved PARP and phosphorylated histone H2AX as well as elevated caspase3/7, 8 and 9 activities. The decreased expression of Bcl-2, MMP-2 and MMP-9 alone with cytochrome c release from mitochondria into the cytosol was also observed in the TMZ/PYR combination group. The increase in cell apoptosis due to combination with PYR was rescued by leucovorin. These data suggest that PYR may enhance the efficacy of TMZ via triggering both cathepsin B-dependent and caspase-dependent apoptotic pathways. Therefore, combination of PYR and TMZ may provide a novel regimen for invasive PAs refractory to standard therapy and TMZ.Pituitary adenomas (PAs) are the second most common intracranial neoplasms, accounting for approximately 15% of primary intracranial tumors. 1 Although most PAs are benign and grow expansively, approximately 35% are locally invasive and aggressive pituitary tumors with massive invasion of bone, dura and/or adjacent structures, and undergo rapid growth. 2 A subset of nonmetastatic invasive pituitary tumors displaying more aggressive behavior are called atypical PAs, and are characterized by fast invasive growth, increased mitotic activity, a Ki-67 labeling index greater than 3% and positive P53 immunoreactivity. 3 Although repeated surgeries, radiosurgery and alternative medical therapies are routinely used for invasive PAs and atypical PAs, they are generally refractory to these therapies and experience tumor recurrence. 4,5 Therefore, it is difficult to manage these invasive PAs owing to their size, invasiveness, accelerated growth and limited therapeutic options.Different chemotherapeutic agents have been tested for refractory PAs to inhibit tumor growth and improve prognosis. Recent case reports have documented that temozolomide (TMZ) has antitumor activity against these tumors. However, only 60% of the published cases responded to TMZ therapy, and exhibited a reduction in tumor mass, normalization of hormone levels and/or prevention of tumor regrowth. 6 A large number of invasive PAs failed to respond to TMZ and