Mark E. Prince

Identification of a subpopulation of cells with cancer stem cell properties in head and neck squamous cell carcinoma

Like many epithelial tumors, head and neck squamous cell carcinoma (HNSCC) contains a heterogeneous population of cancer cells. We developed an immunodeficient mouse model to test the tumorigenic potential of different populations of cancer cells derived from primary, unmanipulated human HNSCC samples. We show that a minority population of CD44+ cancer cells, which typically comprise <10% of the cells in a HNSCC tumor, but not the CD44− cancer cells, gave rise to new tumors in vivo. Immunohistochemistry revealed that the CD44+ cancer cells have a primitive cellular morphology and costain with the basal cell marker Cytokeratin 5/14, whereas the CD44− cancer cells resemble differentiated squamous epithelium and express the differentiation marker Involucrin. The tumors that arose from purified CD44+ cells reproduced the original tumor heterogeneity and could be serially passaged, thus demonstrating the two defining properties of stem cells: ability to self-renew and to differentiate. Furthermore, the tumorigenic CD44+ cells differentially express the BMI1 gene, at both the RNA and protein levels. By immunohistochemical analysis, the CD44+ cells in the tumor express high levels of nuclear BMI1, and are arrayed in characteristic tumor microdomains. BMI1 has been demonstrated to play a role in self-renewal in other stem cell types and to be involved in tumorigenesis. Taken together, these data demonstrate that cells within the CD44+ population of human HNSCC possess the unique properties of cancer stem cells in functional assays for cancer stem cell self-renewal and differentiation and form unique histological microdomains that may aid in cancer diagnosis.

EGFR, p16, HPV Titer, Bcl-xL and p53, Sex, and Smoking As Indicators of Response to Therapy and Survival in Oropharyngeal Cancer

PURPOSE To prospectively identify markers of response to therapy and outcome in an organ-sparing trial for advanced oropharyngeal cancer. PATIENTS AND METHODS Pretreatment biopsies were examined for expression of epidermal growth factor receptor (EGFR), p16, Bcl-xL, and p53 as well as for p53 mutation. These markers were assessed for association with high-risk human papillomavirus (HPV), response to therapy, and survival. Patient variables included smoking history, sex, age, primary site, tumor stage, and nodal status. RESULTS EGFR expression was inversely associated with response to induction chemotherapy (IC) (P = .01), chemotherapy/radiotherapy (CRT; P = .055), overall survival (OS; P = .001), and disease-specific survival (DSS; P = .002) and was directly associated with current smoking (P = .04), female sex (P = .053), and lower HPV titer (P = .03). HPV titer was significantly associated with p16 expression (P < .0001); p16 was significantly associated with response to IC (P = .008), CRT (P = .009), OS (P = .001), and DSS (P = .003). As combined markers, lower HPV titer and high EGFR expression were associated with worse OS (rho(EGFR) = 0.008; rho(HPV) = 0.03) and DSS (rho(EGFR) = 0.01; rho(HPV) = 0.016). In 36 of 42 biopsies, p53 was wild-type, and only one HPV-positive tumor had mutant p53. The combination of low p53 and high Bcl-xL expression was associated with poor OS (P = .005) and DSS (P = .002). CONCLUSION Low EGFR and high p16 (or higher HPV titer) expression are markers of good response to organ-sparing therapy and outcome, whereas high EGFR expression, combined low p53/high Bcl-xL expression, female sex, and smoking are associated with a poor outcome. Smoking cessation and strategies to target EGFR and Bcl-xL are important adjuncts to the treatment of oropharyngeal cancer.

Chemoselection As a Strategy for Organ Preservation in Advanced Oropharynx Cancer: Response and Survival Positively Associated With HPV16 Copy Number

PURPOSE To test induction chemotherapy (IC) followed by concurrent chemoradiotherapy (CRT) or surgery/radiotherapy (RT) for advanced oropharyngeal cancer and to assess the effect of human papilloma virus (HPV) on response and outcome. PATIENTS AND METHODS Sixty-six patients (51 male; 15 female) with stage III to IV squamous cell carcinoma of the oropharynx (SCCOP) were treated with one cycle of cisplatin (100 mg/m(2)) or carboplatin (AUC 6) and with fluorouracil (1,000 mg/m(2)/d for 5 days) to select candidates for CRT. Those achieving a greater than 50% response at the primary tumor received CRT (70 Gy; 35 fractions with concurrent cisplatin 100 mg/m(2) or carboplatin (AUC 6) every 21 days for three cycles). Adjuvant paclitaxel was given to patients who were complete histologic responders. Patients with a response of 50% or less underwent definitive surgery and postoperative radiation. Pretreatment biopsies from 42 patients were tested for high-risk HPV. RESULTS Fifty-four of 66 patients (81%) had a greater than 50% response after IC. Of these, 53 (98%) received CRT, and 49 (92%) obtained complete histologic response with a 73.4% (47 of 64) rate of organ preservation. The 4-year overall survival (OS) was 70.4%, and the disease-specific survival (DSS) was 75.8% (median follow-up, 64.1 months). HPV16, found in 27 of 42 (64.3%) biopsies, was associated with younger age (median, 55 v 63 years; P = .016), sex (22 of 30 males [73.3%] and five of 12 females [41.7%]; P = .08), and nonsmoking status (P = .037). HPV titer was significantly associated with IC response (P = .001), CRT response (P = .005), OS (P = .007), and DSS (P = .008). CONCLUSION Although the numbers in this study are small, IC followed by CRT is an effective treatment for SCCOP, especially in patients with HPV-positive tumors; however, for patients who do not respond to treatment, alternative treatments must be developed.

Single-marker identification of head and neck squamous cell carcinoma cancer stem cells with aldehyde dehydrogenase

In accord with the cancer stem cell (CSC) theory, only a small subset of cancer cells are capable of forming tumors. We previously reported that CD44 isolates tumorigenic cells from head and neck squamous cell cancer (HNSCC). Recent studies indicate that aldehyde dehydrogenase (ALDH) activity may represent a more specific marker of CSCs.

Intensity-Modulated Chemoradiotherapy Aiming to Reduce Dysphagia in Patients With Oropharyngeal Cancer: Clinical and Functional Results

PURPOSE To assess clinical and functional results of chemoradiotherapy for oropharyngeal cancer (OPC), utilizing intensity-modulated radiotherapy (IMRT) to spare the important swallowing structures to reduce post-therapy dysphagia. PATIENTS AND METHODS This was a prospective study of weekly chemotherapy (carboplatin dosed at one times the area under the curve [AUC, AUC 1] and paclitaxel 30 mg/m(2)) concurrent with IMRT aiming to spare noninvolved parts of the swallowing structures: pharyngeal constrictors, glottic and supraglottic larynx, and esophagus as well as the oral cavity and major salivary glands. Swallowing was assessed by patient-reported Swallowing and Eating Domain scores, observer-rated scores, and videofluoroscopy (VF) before therapy and periodically after therapy through 2 years. RESULTS Overall, 73 patients with stages III to IV OPC participated. At a median follow-up of 36 months, 3-year disease-free and locoregional recurrence-free survivals were 88% and 96%, respectively. All measures of dysphagia worsened soon after therapy; observer-rated and patient-reported scores recovered over time, but VF scores did not. At 1 year after therapy, observer-rated dysphagia was absent or minimal (scores 0 to 1) in all patients except four: one who was feeding-tube dependent and three who required soft diet. From pretherapy to 12 months post-therapy, the Swallowing and Eating Domain scores worsened on average (+/- standard deviation) by 10 +/- 21 and 13 +/- 19, respectively (on scales of 0 to 100), and VF scores (on scale of 1 to 7) worsened from 2.9 +/- 1.5 (mild dysphagia) to 4.1 +/- 0.9 (mild/moderate dysphagia). CONCLUSION Chemoradiotherapy with IMRT aiming to reduce dysphagia can be performed safely for OPC and has high locoregional tumor control rates. On average, long-term patient-reported, observer-rated, and objective measures of swallowing were only slightly worse than pretherapy measures, representing potential improvement compared with previous studies.

Tobacco Use in Human Papillomavirus–Positive Advanced Oropharynx Cancer Patients Related to Increased Risk of Distant Metastases and Tumor Recurrence

Purpose: The goal of this study was to examine the effect of tobacco use on disease recurrence (local/regional recurrence, distant metastasis, or second primary) among patients with human papillomavirus (HPV)–positive squamous cell carcinoma of the oropharynx (SCCOP) following a complete response to chemoradiation therapy. Experimental Design: Between 1999 and 2007, 124 patients with advanced SCCOP (86% with stage IV) and adequate tumor tissue for HPV analysis who were enrolled in one of two consecutive University of Michigan treatment protocols were prospectively included in this study. Patients were categorized as never-, former, or current tobacco users. The primary end points were risk of disease recurrence and time to recurrence; secondary end points were disease-specific survival and overall survival. Results: One hundred and two patients (82.3%) had HPV-positive tumors. Over two thirds (68%) of patients with HPV-positive tumors were tobacco users. Among HPV-positive patients, current tobacco users were at significantly higher risk of disease recurrence than never-tobacco users (hazard ratio, 5.2; confidence interval, 1.1-24.4; P = 0.038). Thirty-five percent of HPV-positive ever tobacco users recurred compared with only 6% of HPV-positive never users and 50% of HPV-negative patients. All HPV-negative patients were tobacco users and had significantly shorter times to recurrence (P = 0.002), and had reduced disease-specific survival (P = 0.004) and overall survival (P < 0.001) compared with HPV-positive patients. Compared with HPV-positive never-tobacco users, those with a tobacco history showed a trend for reduced disease-specific survival (P = 0.064) but not overall survival (P = 0.221). Conclusions: Current tobacco users with advanced, HPV-positive SCCOP are at higher risk of disease recurrence compared with never-tobacco users. Clin Cancer Res; 16(4); 1226–35

Single-Cycle Induction Chemotherapy Selects Patients With Advanced Laryngeal Cancer for Combined Chemoradiation: A New Treatment Paradigm

PURPOSE Primary chemoradiotherapy in patients with advanced laryngeal cancer can achieve high rates of organ preservation without sacrificing survival compared with radiation alone or conventional laryngectomy. Appropriate selection of patients for organ preservation approaches could enhance overall treatment outcome and quality of life. We conducted a phase II organ preservation trial for patients with stage III and IV larynx cancer to determine whether late salvage surgery rates could be decreased and survival improved by selecting patients for organ preservation based on response to a single cycle of induction chemotherapy. PATIENTS AND METHODS The chemotherapy was cisplatin 100 mg/m2 on day 1 and fluorouracil 1,000 mg/m(2)/d for 5 days. Patients who achieved less than 50% response had immediate laryngectomy. Patients who achieved more than 50% response went on to concurrent chemoradiotherapy. Histologic complete responders after chemoradiotherapy received two more cycles of chemotherapy. Patients with residual disease after chemoradiotherapy had planned salvage surgery. RESULTS Of 97 eligible patients, 73 (75%) achieved more than 50% response and received chemoradiotherapy. A total of 29 patients (30%) had salvage surgery; 19 patients (20%) had early salvage surgery after the single cycle of induction chemotherapy, three patients (3%) had late salvage surgery after chemoradiotherapy, six patients (6%) eventually had salvage surgery for recurrence, and one patient had laryngectomy for chondroradionecrosis. The median follow-up time was 41.9 months. The overall survival rate at 3 years is 85%. The cause-specific survival rate was 87%. Larynx preservation was achieved in 69 patients (70%). CONCLUSION These results confirm excellent larynx preservation and improved overall survival rates compared with historical results.

Endothelial Cell-Initiated Signaling Promotes the Survival and Self-Renewal of Cancer Stem Cells

Recent studies have demonstrated that cancer stem cells play an important role in the pathobiology of head and neck squamous cell carcinomas (HNSCC). However, little is known about functional interactions between head and neck cancer stem-like cells (CSC) and surrounding stromal cells. Here, we used aldehyde dehydrogenase activity and CD44 expression to sort putative stem cells from primary human HNSCC. Implantation of 1,000 CSC (ALDH+CD44+Lin-) led to tumors in 13 (out of 15) mice, whereas 10,000 noncancer stem cells (ALDH-CD44-Lin-) resulted in 2 tumors in 15 mice. These data demonstrated that ALDH and CD44 select a subpopulation of cells that are highly tumorigenic. The ability to self-renew was confirmed by the observation that ALDH+CD44+Lin- cells sorted from human HNSCC formed more spheroids (orospheres) in 3-D agarose matrices or ultra-low attachment plates than controls and were serially passaged in vivo. We observed that approximately 80% of the CSC were located in close proximity (within 100-μm radius) of blood vessels in human tumors, suggesting the existence of perivascular niches in HNSCC. In vitro studies demonstrated that endothelial cell-secreted factors promoted self-renewal of CSC, as demonstrated by the upregulation of Bmi-1 expression and the increase in the number of orospheres as compared with controls. Notably, selective ablation of tumor-associated endothelial cells stably transduced with a caspase-based artificial death switch (iCaspase-9) caused a marked reduction in the fraction of CSC in xenograft tumors. Collectively, these findings indicate that endothelial cell-initiated signaling can enhance the survival and self-renewal of head and neck CSC.

Cancer Stem Cells in Head and Neck Squamous Cell Cancer

Appropriate treatment of head and neck squamous cell cancer (HNSCC) remains one of the most difficult challenges in head and neck oncology. Overall survival of patients with HNSCC remains at approximately 50% at 5 years. Surgical therapy can be mutilating and often has significant effects on swallowing, speech, and physical appearance. The addition of chemotherapy to radiation treatment has shown efficacy in organ preservation in some sites in the head and neck, but has resulted in limited improvement in survival rates. HNSCC resistance to chemotherapy has limited the usefulness of chemotherapy in the treatment of this disease. We have recently demonstrated that human head and neck squamous cell cancers contain a tumorigenic, so-called cancer stem cell, subpopulation of cells that can self-renew and produce differentiated cells that form the bulk of the tumor. These tumorigenic HNSCC cells have a distinct phenotype and can be identified by a surface marker. Current treatment for HNSCC regimens may selectively kill the differentiated cancer cells, producing tumor regression while sparing the cancer stem cells, leading to tumor regrowth and relapse. It is important for us to understand why HNSCC does not respond to chemotherapy and to identify new targeted treatments that can overcome resistance and improve patient outcomes. Further study of HNSCC stem cells will increase our knowledge of this devastating disease and allow us to develop novel treatments.

Cancer Stem Cell Vaccination Confers Significant Antitumor Immunity

Most studies of cancer stem cells (CSC) involve the inoculation of cells from human tumors into immunosuppressed mice, preventing an assessment on the immunologic interactions and effects of CSCs. In this study, we examined the vaccination effects produced by CSC-enriched populations from histologically distinct murine tumors after their inoculation into different syngeneic immunocompetent hosts. Enriched CSCs were immunogenic and more effective as an antigen source than unselected tumor cells in inducing protective antitumor immunity. Immune sera from CSC-vaccinated hosts contained high levels of IgG which bound to CSCs, resulting in CSC lysis in the presence of complement. CTLs generated from peripheral blood mononuclear cells or splenocytes harvested from CSC-vaccinated hosts were capable of killing CSCs in vitro. Mechanistic investigations established that CSC-primed antibodies and T cells were capable of selective targeting CSCs and conferring antitumor immunity. Together, these proof-of-concept results provide a rationale for a new type of cancer immunotherapy based on the development of CSC vaccines that can specifically target CSCs.