Combination therapy of 7-O-succinyl macrolactin A tromethamine salt and temozolomide against experimental glioblastoma

The Combination PARP Inhibitor Olaparib With Temozolomide in an Experimental Glioblastoma Model

BACKGROUND/AIM

Poly (ADP-ribose) polymerase (PARP) inhibition could enhance the efficacy of temozolomide and prolong survival in patients with glioblastoma. The aim of this study was to evaluate the combination of the PARP inhibitor olaparib with temozolomide in the treatment of glioblastoma.

MATERIALS AND METHODS

The in vitro and in vivo antitumor effects of the PARP inhibitor olaparib together with temozolomide were evaluated. The in vitro experimental glioblastoma model involved O⁶-methylguanine methyltransferase (MGMT) promoter-methylated (U87MG, U251MG) and MGMT promoter-unmethylated (T98G) glioblastoma cell lines using In this model cell viability and apoptosis were assessed. For the in vivo studies, nude mice bearing orthotopically xenografted glioblastoma cell lines (U87MG) were randomized to four experimental groups: i) the untreated, ii) temozolomide alone, iii) olaparib alone and iv) olaparib and temozolomide combination groups. Mice were treated daily for 4 weeks and monitored for tumor growth and survival.

RESULTS

In vitro we found that the combination of olaparib with temozolomide enhanced temozolomide-induced cytotoxicity in all glioblastoma cell lines regardless of the status of MGMT promoter methylation. In vivo, mice treated with temozolomide alone or in combination with olaparib showed greater survival than those untreated or with the olaparib monotherapy, as well as significantly decreased tumor volume. There was no significant difference in survival and tumor volume between temozolomide alone and the combination treatment.

CONCLUSION

The combination of the PARP inhibitor olaparib with temozolomide could be promising candidates for combination therapy of glioblastoma regardless of the MGMT promoter methylation status.

Macrolactins: biological activity and biosynthesis

Marine microorganisms have proven to be a rich source of natural products with unique structures and novel activities, due to their special living conditions. Macrolactins (MLNs), mostly produced by marine-derived microorganisms, are a group of 24-membered lactone natural products, which exhibit potent antibacterial, antifungal, antiviral, anticancer, anti-inflammatory, anti-angiogenic and other activities. Their extensive biological activities make them potential compounds for drug development. MLNs are biosynthesized via a type I polyketide synthase (PKS) pathway with different tailoring steps, such as epoxidation, glycosylation and acylation. These modification steps provide opportunities to diversify their structures by combinatorial biosynthesis strategies. This review mainly focuses on the newly discovered MLNs in the past five years, including their biological activities and relevant biosynthetic studies.

The combined efficacy of OTS964 and temozolomide for reducing the size of power-law coded heterogeneous glioma stem cell populations

Glioblastoma resists chemotherapy then recurs as a fatal space-occupying lesion. To improve the prognosis, the issues of chemoresistance and tumor size should be addressed. Glioma stem cell (GSC) populations, a heterogeneous power-law coded population in glioblastoma, are believed to be responsible for the recurrence and progressive expansion of tumors. Thus, we propose a therapeutic strategy of reducing the initial size and controlling the regrowth of GSC populations which directly facilitates initial and long-term control of glioblastoma recurrence. In this study, we administered an anti-glioma/GSC drug temozolomide (TMZ) and OTS964, an inhibitor for T-Lak cell originated protein kinase, in combination (T&O), investigating whether together they efficiently and substantially shrink the initial size of power-law coded GSC populations and slow the long-term re-growth of drug-resistant GSC populations. We employed a detailed quantitative approach using clonal glioma sphere (GS) cultures, measuring sphere survivability and changes to growth during the self-renewal. T&O eliminated self-renewing GS clones and suppressed their growth. We also addressed whether T&O reduced the size of self-renewed GS populations. T&O quickly reduced the size of GS populations via efficient elimination of GS clones. The growth of the surviving T&O-resistant GS populations was continuously disturbed, leading to substantial long-term shrinkage of the self-renewed GS populations. Thus, T&O reduced the initial size of GS populations and suppressed their later regrowth. A combination therapy of TMZ and OTS964 would represent a novel therapeutic paradigm with the potential for long-term control of glioblastoma recurrence via immediate and sustained shrinkage of power-law coded heterogeneous GSC populations.

Newcastle disease virus enhances the growth-inhibiting and proapoptotic effects of temozolomide on glioblastoma cells in vitro and in vivo

Glioblastoma (GBM) is the most serious and most common brain tumor in humans. Despite recent advances in the diagnosis of GBM and the development of new treatments, the prognosis of patients has not improved. Multidrug resistance, particularly resistance to temozolomide (TMZ), is a challenge in combating glioma, and more effective therapies are needed. Complementary treatment with the LaSota strain of the naturally oncolytic Newcastle disease virus (NDV-LaSota) is an innovation. In our experiments, the combination therapy of NDV-LaSota and temozolomide (TMZ) was more effective than either treatment alone in inducing apoptosis in glioma cells. NDV can function as a tumor cell selective approach to inhibit AKT and activate AMPK. Consequently, mTOR, 4EBP1 and S6K were also suppressed. The combination therapy of NDV and TMZ also significantly extended survival in a rat xenograft tumor model. In conclusion, NDV suppress AKT signaling and enhances antitumor effects of TMZ. Our study provides one of the theoretical basis for the use of a combined therapy of TMZ and NDV, which could benefit GBM patients.