Yuh Baba

Acidic extracellular microenvironment and cancer

Acidic extracellular pH is a major feature of tumor tissue, extracellular acidification being primarily considered to be due to lactate secretion from anaerobic glycolysis. Clinicopathological evidence shows that transporters and pumps contribute to H+ secretion, such as the Na+/H+ exchanger, the H+-lactate co-transporter, monocarboxylate transporters, and the proton pump (H+-ATPase); these may also be associated with tumor metastasis. An acidic extracellular pH not only activates secreted lysosomal enzymes that have an optimal pH in the acidic range, but induces the expression of certain genes of pro-metastatic factors through an intracellular signaling cascade that is different from hypoxia. In addition to lactate, CO2 from the pentose phosphate pathway is an alternative source of acidity, showing that hypoxia and extracellular acidity are, while being independent from each other, deeply associated with the cellular microenvironment. In this article, the importance of an acidic extracellular pH as a microenvironmental factor participating in tumor progression is reviewed.

Reduction of in vivo tumor growth by MMI-166, a selective matrix metalloproteinase inhibitor, through inhibition of tumor angiogenesis in squamous cell carcinoma cell lines of head and neck

Matrix metalloproteinases (MMPs) have been implicated in tumor invasion, metastasis, and angiogenesis. We have recently shown that MMI-166, a new orally active MMP inhibitor specific for MMP-2 and -9, suppressed experimental metastasis of Lewis lung cancer, C-H1 human colon cancer, and pancreatic cancer without affecting tumor growth in vitro. In the present study, we determined whether oral administration of MMI-166 reduces tumor growth not only in such tumors but also in squamous cell carcinoma of head and neck (SCCHN). MMI-166 inhibited both activity of MMP-2 and -9 without affecting steady state levels of their mRNAs in SCCHN. Interestingly, protein levels of MMP-2 and -9 from the cultures were drastically diminished by culturing with MMI-166. This was also observed in xenografts of MMI-166-administered mice. In addition, daily oral administration of MMI-166 (100mg/kg) inhibited local tumor growth accompanied by the reduction of blood vessel density and Ki-67-positivity and increase in terminal deoxynucleotidyl transferase-mediated cUDP nick-end labeling (TUNEL)-positivity. These results suggested that orally administered MMI-166 reduced in vivo tumor growth of SCCHN through inhibition of angiogenesis and induction of apoptosis accompanied by the reduction of MMP productions and activities. Therefore, MMI-166 seems to be useful for tumor dormancy therapy of SCCHN.

Inostamycin, an inhibitor of cytidine 5′-diphosphate 1,2-diacyl-sn-glycerol (CDP-DG): Inositol transferase, suppresses invasion ability by reducing productions of matrix metalloproteinase-2 and -9 and cell motility in HSC-4 tongue carcinoma cell line

Inostamycin is an inhibitor of cytidine 5′-diphosphate 1,2-diacyl-sn-glycerol (CDP-DG): inositol transferase. It significantly reduced epidermal growth factor (EGF)-induced in vitro invasion of the tongue carcinoma cell line, HSC-4, through reconstituted basement membrane Matrigel®. Since phosphatidylinositol (PI) 4,5-biphosphate is important for signal transduction through protein kinase C and actin reorganisation, we further examined the effect of inostamycin on production of two matrix metalloproteinases (MMPs), MMP-2 and -9, and on cell motility. Zymographic analysis showed that inostamycin suppressed pro-MMP-2 and pro-MMP-9 levels at a dose-dependent fashion, while MMP-2 activity was not significantly affected. By reverse transcription-polymerase chain reaction, it was found that inostamycin diminished steady state levels of MMP-2 and -9 but not membrane type 1-MMP mRNA expressions. Inostamycin partially blocked both EGF- and phorbol 12-myristate 13-acetate-stimulated pro-MMP- 9 production. A cytoplasmic calcium chelator (BAPTA-AM) dramatically elevated pro- MMP-9 and slightly elevated pro-MMP-2 secretions. EGF-stimulated motility of HSC-4 cells was suppressed by inostamycin treatment along with reduction of actin cytoskeletal reorganisation, filopodia formation and cdc42 expression. These results suggested that inostamycin would be useful for an anti-invasive agent in tongue cancer.

Present and Future of EGFR Inhibitors for Head and Neck Squamous Cell Cancer.

Although EGFR is expressed at high levels in head and neck squamous cell carcinomas (HNSCCs) and mutations are extremely rare, monotherapy with EGFR inhibitors has shown limited success. The PI3kinase/Akt pathway is responsible for cellular survival, and inhibition of phosphatidylinositol (PI) synthesis has antiproliferative, anti-invasive, and antiangiogenesis effects on HNSCC. Molecular crosstalk has been observed between EGFR and IGF1R signaling through the PI3kinase/Akt pathway in HNSCC, as has molecular crosstalk between the NFκB and STAT3 signaling pathways. Therefore, the combination of an EGFR antagonist with an agent that inhibits the activation of both Akt and NFκB may overcome resistance to EGFR antagonists in HNSCC.

Cyclin D1 expression as a prognostic factor in advanced hypopharyngeal carcinoma.

Hypopharyngeal carcinoma (HPC) has a poor prognosis. We investigated the expression of cyclin D1 in 34 advanced HPCs, and the value of cyclin D1 expression was evaluated as a predictive marker in terms of the prognosis of HPC, compared with other clinical factors. Using immunohistochemical staining, 20 of 34 patients showed positive immunoreactivity for cyclin D1. The statistical trend of the survival rate was lower in the cyclin D1-positive patients than in the cyclin D-negative ones (p = 0.0805). The predictive factors for the survival rate were effectiveness of neo-adjuvant chemotherapy (F = 8.698) (p = 0.0066), cyclin D1 expression (F = 6.244) (p = 0.0191) and N classification (F = 5.037) (p = 0.0335). The cyclin D1-positive patients had approximately four-fold higher mortality than the cyclin D1-negative ones. These data indicate that the expression of cyclin D1, in advanced patients with hypopharyngeal carcinoma is a useful marker for prognosis.

Cytostatic effect of inostamycin, an inhibitor of cytidine 5'-diphosphate 1,2-diacyl-sn-glycerol (CDP-DG): inositol transferase, on oral squamous cell carcinoma cell lines.

Inostamycin, which was recently isolated from Streptomyces sp. MH816‐AF15 as an inhibitor of cytidine 5′‐diphosphate 1,2‐diacyl‐sn‐glycerol (CDP‐DG): inositol transferase, caused a G1‐phase accumulation in the cell cycle of small cell lung carcinomas. To investigate whether the cytostatic effect of inostamycin is restricted to lung carcinoma cell lines or applicable to other type of cells, we tested five oral squamous cell carcinoma (SCC) cell lines. Cell growth was suppressed in 62.5–125ng/ml inostamycin in the culture medium in all oral cancer cell lines tested, with non‐viable cells being <1%, indicating inostamycin is cytostatic on SCC cell lines. Decrease in cyclin D1 mRNA and protein expression due to the inostamycin treatment was accompanied by suppression of phosphorylated retinoblastoma susceptibility gene product (pRB‐P) levels. Moreover, flow cytometric analysis showed that inostamycin induced an increase in G1/G0 cells (1.2–3.2 fold) over 24h. These results suggest that inostamycin is a useful agent for tumour dormant cytostatic therapy for oral SCC.

Deguelin Induces Apoptosis by Targeting Both EGFR-Akt and IGF1R-Akt Pathways in Head and Neck Squamous Cell Cancer Cell Lines

Deguelin, a rotenoid compound from the African plant Mundulea sericea (Leguminosae), has been shown to possess antitumor activities but the exact role for the growth factor receptor mediated signaling pathway in head and neck squamous cell carcinoma (HNSCC) is currently still unclear. In the present study, we investigated the effect of deguelin on epidermal growth factor receptor (EGFR) and insulin-like growth factor-1 receptor (IGF1R) pathways in HNSCC cell lines. Flowcytometric analysis revealed accumulation of annexin V positivity in deguelin-treated cells, showing that deguelin induced apoptosis. The deguelin-induced apoptosis was accompanied by the reduction of constitutive phosphorylated levels of IGF1R, Akt, and extracellular signal-regulated kinase1/2 (ERK1/2). LY294002-mediated inhibition of phosphatidylinositol-3 kinase, which is an upstream effector for Akt activation, increased cleavage of poly(ADP-ribosyl) polymerase (PARP) but ERK inhibition by U0126 did not. Deguelin inhibited both IGF-1- and EGF-induced Akt activation. These results showed that deguelin possessed antitumor effect by targeting Akt in dual axis such as EGFR and IGF1R signaling pathways and suggested that it provides an applicable therapeutic strategy for HNSCC patients.

Inostamycin suppresses vascular endothelial growth factor-stimulated growth and migration of human umbilical vein endothelial cells

Angiogenesis involves multiple steps including proliferation and migration of endothelial cells. In the present study, we determined the effect of inostamycin (an inhibitor of phosphatidylinositol synthesis) on vascular endothelial growth factor (VEGF)-induced proliferation and migration of human umbilical vein endothelial cells (HUVECs). Inostamycin significantly attenuated both VEGF-induced proliferation and migration of HUVECs. Inostamycin inhibited activation of mitogen-activated kinases (ERK and p38) and elevation of cyclin D1 induced by VEGF. These data suggest that inostamycin reduced both proliferation and migration of HUVECs by targeting ERK-cyclin D1 and p38, respectively.

Inostamycin prevents malignant phenotype of cancer: inhibition of phosphatidylinositol synthesis provides a therapeutic advantage for head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma is the sixth most common type of neoplasm worldwide, but its prognosis has not improved significantly in recent years. Therefore, efforts need to be intensified to gain a better understanding of this disease and develop novel treatment strategies. Inhibition of cytidine 5′‐diphosphate 1,2‐diacyl‐sn‐glycerol: inositol transferase by inostamycin, an antibiotic isolated from Streptomyces sp. MH816‐AF15, induces G1 cell cycle arrest accompanied by a decrease in cyclin D1 and phosphorylated RB protein levels, along with suppression of in vitro invasive ability through reduced production of matrix metalloproteinases (MMP‐2 and MMP‐9) and cell motility in head and neck cancer cell lines. Furthermore, inostamycin abrogated the stimulatory effect of VEGF (vascular endothelial growth factor) on growth and migration activities of endothelial cells by targeting extracellular signal‐regulated kinase‐cyclin D1 and p38 pathways, respectively. Because inostamycin has both antiproliferative and anti‐invasive abilities, inhibition of phosphatidylinositol synthesis could be a potent therapeutic strategy for head and neck cancer as the ‘cancer dormant therapy’, i.e. a therapeutic concept to prolong ‘time to treatment failure’ or ‘time to progression’.

Unusual computed tomography findings of radionecrosis after chemoradiation of stage IV hypopharyngeal cancer: a case report

IntroductionRadionecrosis (post-radiotherapy laryngeal submucosal inflammation and necrosis) is a complication of (chemo) radiotherapy for hypopharyngeal cancer that is difficult to differentiate from tumor recurrence.Case presentationA 67-year-old Japanese man presented with a condition extremely difficult to diagnose differentially as radionecrosis or tumor recurrence after radiotherapy for hypopharyngeal cancer. Although tumor recurrence was suspected from clinical conditions and computed tomography findings, pathologic analysis revealed no evidence of tumor recurrence, and successful therapy with steroids and antibiotics reduced the mucosal edema.ConclusionOur findings emphasize the wide spectrum of radiographic presentation of radionecrosis after chemoradiation of stage IV hypopharyngeal cancer.