Blockade of Cell Volume Regulatory Protein NKCC1 Increases TMZ-Induced Glioma Apoptosis and Reduces Astrogliosis

Abstract

Glioma is one of the most common primary malignant tumors of the central nervous system accounting for approximately 40% of all intracranial tumors. Temozolomide is a conventional chemotherapy drug for adjuvant treatment of patients with high-risk gliomas, including grade II to grade IV. Our bioinformatic analysis of The Cancer Genome Atlas and Chinese Glioma Genome Atlas datasets and immunoblotting assay show that SLC12A2 gene and its encoded Na+-K+-2Cl− cotransporter isoform 1 (NKCC1) protein are abundantly expressed in grade II–IV gliomas. NKCC1 regulates cell volume and intracellular Cl− concentration, which promotes glioma cell migration, resistance to temozolomide, and tumor-related epilepsy in experimental glioma models. Using mouse syngeneic glioma models with intracranial transplantation of two different glioma cell lines (GL26 and SB28), we show that NKCC1 protein in glioma tumor cells as well as in tumor-associated reactive astrocytes was significantly upregulated in response to temozolomide monotherapy. Combination therapy of temozolomide with the potent NKCC1 inhibitor bumetanide reduced tumor proliferation, potentiated the cytotoxic effects of temozolomide, decreased tumor-associated reactive astrogliosis, and restored astrocytic GLT-1 and GLAST glutamate transporter expression. The combinatorial therapy also led to suppressed tumor growth and prolonged survival of mice bearing GL26 glioma cells. Taken together, these results demonstrate that NKCC1 protein plays multifaceted roles in the pathogenesis of glioma tumors and presents as a therapeutic target for reducing temozolomide-mediated resistance and tumor-associated astrogliosis.

Deeper and Deeper on the Role of BK and Kir4.1 Channels in Glioblastoma Invasiveness: A Novel Summative Mechanism?

“…The overexpression of the NKCC1 cotransporter leads to abnormal accumulation of Cl − in the glioma cell cytosol (Haas and Sontheimer, 2010;Ben-Ari, 2017) so that upon opening of Cl − channels (Barbieri et al, 2018), the altered electrochemical gradient results in an outward flow of this ion with concomitant osmotic loss of water from the intracellular milieu (through the aquaporin channels). The net result is a loss of cellular volume (Luo et al, 2020).…”

Application of intraoperative B-mode ultrasound and shear wave elastography for glioma grading

“…Glioma is the most common neuroepithelial tumor, accounting for about 40% of primary intracranial tumors (1), and those of a high-grade are characterized by rapid progression, severe symptoms, and poor quality of life. The 5-year survival rate of glioblastoma (GBM) is less than 5%, with a median survival of approximately 14 months (2,3), and while surgical resection is the current primary treatment approach, the postoperative residual tumor is an important factor in the prognosis of patients (4,5).…”

Role of NKCC1 Activity in Glioma K+ Homeostasis and Cell Growth: New Insights With the Bumetanide-Derivative STS66

“…A growing body of evidence indicates that expression of NKCC1 protein is closely related to tumor progression, such as lung adenocarcinoma (Sun et al, 2016), prostate cancer cells (Hiraoka et al, 2010), and esophageal squamous carcinoma cells (Shiozaki et al, 2014). Luo et al showed that NKCC1 protein and messenger RNA (mRNA) are abundantly expressed in all grade of gliomas (Luo et al, 2020). Unlike other cancers that spread through the vasculature, gliomas actively invade surrounding brain solely along extracellular routes (Watkins and Sontheimer, 2011).…”

“…Moreover, NKCC1 protein expression has been shown to associate with glioma cell migration (Zhu et al, 2014) via regulation of focal adhesion dynamics, cell contractility, and cell volume (Haas et al, 2011;Garzon-Muvdi et al, 2012). We have reported recently that temozolomide (TMZ) monotherapy significantly upregulated NKCC1 protein expression and activity (NKCC1-mediated Rb + influx; Luo et al, 2020) to replenish intracellular K + in response to TMZ induced-apoptosis. NKCC1 inhibitor bumetanide (BMT) in combination with TMZ accelerated apoptosis, reduced tumor volume, and potentiated the cytotoxic effects of TMZ in the GL26 and SB28-GFP intracranial mouse syngeneic glioma model (Luo et al, 2020).…”

“…We have reported recently that temozolomide (TMZ) monotherapy significantly upregulated NKCC1 protein expression and activity (NKCC1-mediated Rb + influx; Luo et al, 2020) to replenish intracellular K + in response to TMZ induced-apoptosis. NKCC1 inhibitor bumetanide (BMT) in combination with TMZ accelerated apoptosis, reduced tumor volume, and potentiated the cytotoxic effects of TMZ in the GL26 and SB28-GFP intracranial mouse syngeneic glioma model (Luo et al, 2020).…”