The Akt inhibitor KP372-1 inhibits proliferation and induces apoptosis and anoikis in squamous cell carcinoma of the head and neck.

Therapies that target signaling pathways critical to the pathogenesis and progression of squamous cell carcinoma of the head and neck (HNSCC) are needed. One such target, phosphatidylinositol 3-kinase, and its downstream target serine/threonine kinase, Akt, are up-regulated in HNSCC. Targeted therapy could consist of inhibitors of these kinases or, alternatively, of inhibitors of the pathways that they regulate. To explore the effect of Akt inhibition on the growth and survival of HNSCC tumors, we evaluated the effect of a novel Akt inhibitor, KP372-1, on the growth, survival, and sensitivity to anoikis of HNSCC cell lines in culture. Using Western blotting of head and neck cancer cell lines and squamous mucosa and carcinoma specimens, we found that Akt was highly phosphorylated in head and neck cancer cell lines and human head and neck squamous carcinoma specimens. Treatment of HNSCC cell lines with KP372-1 blocked the activation of Akt, inhibited head and neck cancer cell proliferation, and induced apoptosis and anoikis in several HNSCC cell lines. Furthermore, KP372-1 decreased the phosphorylation of the S6 ribosomal (Ser240/244) protein, which is a downstream target of Akt. Taken together, these findings indicate that KP372-1 may be a useful therapeutic agent for HNSCC and should be further evaluated in preclinical models of HNSCC.

Epidermal growth factor receptor blockade potentiates apoptosis mediated by Paclitaxel and leads to prolonged survival in a murine model of oral cancer.

PURPOSE: Because survival for patients with oral cancer has not improved over the past 25 years, new approaches for treatment are needed. Targeted molecular therapy against epidermal growth factor receptor (EGFR) has shown promise as an adjuvant therapy in preliminary studies in several solid tumors, including head and neck cancer. The objective of this study was to determine the efficacy of paclitaxel and PKI166, a novel inhibitor of EGFR, against oral cavity cancer. EXPERIMENTAL DESIGN AND RESULTS: JMAR human oral cancer cells were pretreated for 1 h with PKI166 and then stimulated with epidermal growth factor. EGFR-specific tyrosine kinase autophosphorylation measured by Western immunoblotting was inhibited by PKI166 in a dose-dependent fashion at all doses tested (0.01-1 micro M). Next, the induction of apoptosis in JMAR cells treated with paclitaxel (0.001 to 0.1 micro M) with or without PKI166 (0, 1, or 2 micro M) was determined using a propidium iodide assay. The addition of 2.0 micro M PKI166 significantly increased tumor cell death, shifting the amount of paclitaxel needed to induce apoptosis in 50% of cells from 0.1 to 0.001 micro M. These in vitro findings were confirmed using an orthotopic model of oral cancer. JMAR oral cancer cells were implanted into the tongues of nude mice. After lingual tumors developed, mice were randomized into four groups (n = 10): (a) oral PKI166 (100 mg/kg); (b) i.p. paclitaxel (200 micro g/wk); (c) PKI166 and paclitaxel; or (d) placebo. Mice treated with PKI166/paclitaxel demonstrated a significant increase in survival (P = 0.028). After necropsy, all tongue tumors were evaluated for apoptosis by the terminal deoxynucleotidyl transferase-mediated nick end labeling assay. A greater apoptotic fraction of tumor cells was found in tumors of mice treated with paclitaxel and PKI166 as compared with the other treatment groups (136.4 versus 37.8; P = 0.016). CONCLUSIONS: Combination therapy with paclitaxel and PKI166 prolongs survival in an orthotopic preclinical model of tongue cancer by increasing programmed cell death of oral cancer.

Acquisition of anoikis resistance is a critical step in the progression of oral tongue cancer.

We hypothesized that acquisition of resistance to anoikis is a critical step in oral cancer progression. To test this hypothesis, we compared a panel of cell lines derived from human oral tissues across the spectrum of tumor progression from oral keratinocytes (HOK-16B), invasive oral squamous cell carcinoma (Tu167), and finally metastatic carcinoma (TxCS-1, MDA1986) for their sensitivity to detachment from the extracellular matrix. The relationship between stage of tumor progression and anoikis resistance was demonstrated by the apoptotic fractions after 48 h in suspension culture which were 93.33, 61.6, 34.5, and 3.71%, respectively. To further demonstrate that anoikis resistance is important for tumor progression, we selected a highly anoikis resistant cell line, JMAR, by serial passage of the Tu167 cell line in suspension culture. Initially, the JMAR line, and clones derived from it, were characterized for anoikis resistance in vitro, and after 72 h in suspension culture the rates of anoikis in the Tu167 and JMAR lines were found to be 73 and 26%, respectively. The degree of anoikis resistance was found to correlate with survival of nude mice orthotopically injected with 5x10(5) Tu167 or JMAR cells. The JMAR mice had a median survival of 17 days versus over 30 days in mice implanted with the Tu167 line. Finally, we found that in vivo selection in the orthotopic model for a regionally metastatic cell line by implantation of Tu167 into the tongues of nude mice and harvesting and culturing cervical lymph nodes led to production of a cell line, Tu167LN1, which was found to be anoikis-resistant. This cell line had an apoptotic cell fraction of 16.2% (+/-3.14%) after 48 h in suspension culture.