Nikolai N. Khodarev

The Efficacy of Radiotherapy Relies upon Induction of Type I Interferon–Dependent Innate and Adaptive Immunity

The most widely held explanation for the efficacy of local radiotherapy (RT) is based on direct cytotoxicity to cancer cells through the induction of lethal DNA damage. Recent studies have shown that local ablative radiation of established tumors can lead to increased T-cell priming and T-cell-dependent tumor regression, but the underlying mechanism remains unclear. Here, we describe an essential role for type I IFN in local RT-mediated tumor control. We show that ablative RT increases intratumoral production of IFN-β and, more surprisingly, the antitumor effect of RT is abolished in type I IFN nonresponsive hosts. Furthermore, the major target of RT-induced type I IFN is the hematopoietic compartment. RT drastically enhances the cross-priming capacity of tumor-infiltrating dendritic cells (TIDC) from wild-type mice but not type I IFN receptor-deficient mice. The enhanced cross-priming ability of TIDCs after RT was dependent on autocrine production of type I IFNs. By using adenoviral-mediated expression of IFN-β, we show that delivery of exogenous IFN-β into the tumor tissue in the absence of RT is also sufficient to selectively expand antigen-specific T cells leading to complete tumor regression. Our study reveals that local high-dose RT can trigger production of type I IFN that initiates a cascading innate and adaptive immune attack on the tumor.

An interferon-related gene signature for DNA damage resistance is a predictive marker for chemotherapy and radiation for breast cancer

Individualization of cancer management requires prognostic markers and therapy-predictive markers. Prognostic markers assess risk of disease progression independent of therapy, whereas therapy-predictive markers identify patients whose disease is sensitive or resistant to treatment. We show that an experimentally derived IFN-related DNA damage resistance signature (IRDS) is associated with resistance to chemotherapy and/or radiation across different cancer cell lines. The IRDS genes STAT1, ISG15, and IFIT1 all mediate experimental resistance. Clinical analyses reveal that IRDS(+) and IRDS(−) states exist among common human cancers. In breast cancer, a seven–gene-pair classifier predicts for efficacy of adjuvant chemotherapy and for local-regional control after radiation. By providing information on treatment sensitivity or resistance, the IRDS improves outcome prediction when combined with standard markers, risk groups, or other genomic classifiers.

Progression of Barrett's Metaplasia to Adenocarcinoma Is Associated with the Suppression of the Transcriptional Programs of Epidermal Differentiation

We did expressional profiling on 24 paired samples of normal esophageal epithelium, Barretts metaplasia, and esophageal adenocarcinomas. Matching tissue samples representing the three different histologic types were obtained from each patient undergoing esophagectomy for adenocarcinoma. Our analysis compared the molecular changes accompanying the transformation of normal squamous epithelium with Barretts esophagus and adenocarcinoma in individual patients rather than in a random cohort. We tested the hypothesis that expressional profiling may reveal gene sets that can be used as molecular markers of progression from normal esophageal epithelium to Barretts esophagus and adenocarcinoma. Expressional profiling was done using U133A GeneChip (Affymetrix), which represent approximately two thirds of the human genome. The final selection of 214 genes permitted the discrimination of differential gene expression of normal esophageal squamous epithelium, Barretts esophagus, and adenocarcinoma using two-dimensional hierarchical clustering of selected genes. These data indicate that transformation of Barretts esophagus to adenocarcinoma is associated with suppression of the genes involved in epidermal differentiation, including genes in 1q21 loci and corresponding to the epidermal differentiation complex. Correlation analysis of genes concordantly expressed in Barretts esophagus and adenocarcinoma revealed 21 genes that represent potential genetic markers of disease progression and pharmacologic targets for treatment intervention. PCR analysis of genes selected based on DNA array experiments revealed that estimation of the ratios of GATA6 to SPRR3 allows discrimination among normal esophageal epithelium, Barretts dysplasia, and adenocarcinoma.

MicroRNA Expression Characterizes Oligometastasis(es)

Background Cancer staging and treatment presumes a division into localized or metastatic disease. We proposed an intermediate state defined by ≤5 cumulative metastasis(es), termed oligometastases. In contrast to widespread polymetastases, oligometastatic patients may benefit from metastasis-directed local treatments. However, many patients who initially present with oligometastases progress to polymetastases. Predictors of progression could improve patient selection for metastasis-directed therapy. Methods Here, we identified patterns of microRNA expression of tumor samples from oligometastatic patients treated with high-dose radiotherapy. Results Patients who failed to develop polymetastases are characterized by unique prioritized features of a microRNA classifier that includes the microRNA-200 family. We created an oligometastatic-polymetastatic xenograft model in which the patient-derived microRNAs discriminated between the two metastatic outcomes. MicroRNA-200c enhancement in an oligometastatic cell line resulted in polymetastatic progression. Conclusions These results demonstrate a biological basis for oligometastases and a potential for using microRNA expression to identify patients most likely to remain oligometastatic after metastasis-directed treatment.

Signal Transducer and Activator of Transcription 1 Regulates Both Cytotoxic and Prosurvival Functions in Tumor Cells

Elsewhere, we reported that multiple serial in vivo passage of a squamous cell carcinoma cells (SCC61) concurrent with ionizing radiation (IR) treatment resulted in the selection of radioresistant tumor (nu61) that overexpresses the signal transducer and activator of transcription 1 (Stat1)/IFN-dependent pathway. Here, we report that (a) the Stat1 pathway is induced by IR, (b) constitutive overexpression of Stat1 is linked with failure to transmit a cytotoxic signal by radiation or IFNs, (c) selection of parental cell line SCC61 against IFN-alpha and IFN-gamma leads to the same IR- and IFN-resistant phenotype as was obtained by IR selection, and (d) suppression of Stat1 by short hairpin RNA renders the IR-resistant nu61 cells radiosensitive to IR. We propose a model that transient induction of Stat1 by IFN, IR, or other stress signals activates cytotoxic genes and cytotoxic response. Constitutive overexpression of Stat1 on the other hand leads to the suppression of the cytotoxic response and induces prosurvival genes that, at high levels of Stat1, render the cells resistant to IR or other inducers of cell death.

STAT1 Pathway Mediates Amplification of Metastatic Potential and Resistance to Therapy

Background Traditionally IFN/STAT1 signaling is connected with an anti-viral response and pro-apoptotic tumor-suppressor functions. Emerging functions of a constitutively activated IFN/STAT1 pathway suggest an association with an aggressive tumor phenotype. We hypothesized that tumor clones that constitutively overexpress this pathway are preferentially selected by the host microenvironment due to a resistance to STAT1-dependent cytotoxicity and demonstrate increased metastatic ability combined with increased resistance to genotoxic stress. Methodology/Principal Findings Here we report that clones of B16F1 tumors grown in the lungs of syngeneic C57BL/6 mice demonstrate variable transcriptional levels of IFN/STAT1 pathway expression. Tumor cells that constitutively overexpress the IFN/STAT1 pathway (STAT1H genotype) are selected by the lung microenvironment. STAT1H tumor cells also demonstrate resistance to IFN-gamma (IFNγ), ionizing radiation (IR), and doxorubicin relative to parental B16F1 and low expressors of the IFN/STAT1 pathway (STAT1L genotype). Stable knockdown of STAT1 reversed the aggressive phenotype and decreased both lung colonization and resistance to genotoxic stress. Conclusions Our results identify a pathway activated by tumor-stromal interactions thereby selecting for pro-metastatic and therapy-resistant tumor clones. New therapies targeted against the IFN/STAT1 signaling pathway may provide an effective strategy to treat or sensitize aggressive tumor clones to conventional cancer therapies and potentially prevent distant organ colonization.

MUC1-induced alterations in a lipid metabolic gene network predict response of human breast cancers to tamoxifen treatment

The mucin 1 (MUC1) oncoprotein is aberrantly overexpressed in human breast cancers. Although MUC1 modulates the activity of estrogen receptor α (ER), there is no information regarding the effects of MUC1 on global gene expression patterns and the potential role of MUC1-induced genes in predicting outcome for breast cancer patients. We have developed an experimental model of MUC1-induced transformation that has identified the activation of genes involved in cholesterol and fatty acid metabolism. A 38-gene set of experimentally derived MUC1-induced genes associated with lipid metabolism was applied to the analysis of ER+ breast cancer patients treated with tamoxifen. The results obtained from 2 independent databases demonstrate that patients overexpressing MUC1 and the lipid metabolic pathways are at significantly higher risk for death and recurrence/distant metastasis. By contrast, these genes were not predictive in untreated patients. Furthermore, a positive correlation was found between expression of the 38-gene set and the ER signaling pathway. These findings indicate that (i) MUC1 regulates cholesterol and fatty acid metabolism, and (ii) activation of these pathways in ER+ breast cancers predicts failure to tamoxifen treatment.

MUC1-induced transcriptional programs associated with tumorigenesis predict outcome in breast and lung cancer.

The Mucin 1 (MUC1) oncoprotein is aberrantly overexpressed in diverse human malignancies including breast and lung cancer. Although MUC1 modulates the activity of several transcription factors, there is no information regarding the effects of MUC1 on global gene expression patterns and the potential role of MUC1-induced genes in predicting outcome for cancer patients. We have developed an experimental model of MUC1-induced transformation that has identified the activation of gene families involved in oncogenesis, angiogenesis, and extracellular matrix remodeling. A set of experimentally derived MUC1-induced genes associated with tumorigenesis was applied to the analysis of breast and lung adenocarcinoma cancer databases. A 35-gene MUC1-induced tumorigenesis signature predicts significant decreases in both disease-free and overall survival in patients with breast (n=295) and lung (n=442) cancers. The data show that the MUC1 oncoprotein contributes to the regulation of genes that are highly predictive of clinical outcome in breast and lung cancer patients.

Oligo- and Polymetastatic Progression in Lung Metastasis(es) Patients Is Associated with Specific MicroRNAs

Rationale Strategies to stage and treat cancer rely on a presumption of either localized or widespread metastatic disease. An intermediate state of metastasis termed oligometastasis(es) characterized by limited progression has been proposed. Oligometastases are amenable to treatment by surgical resection or radiotherapy. Methods We analyzed microRNA expression patterns from lung metastasis samples of patients with ≤5 initial metastases resected with curative intent. Results Patients were stratified into subgroups based on their rate of metastatic progression. We prioritized microRNAs between patients with the highest and lowest rates of recurrence. We designated these as high rate of progression (HRP) and low rate of progression (LRP); the latter group included patients with no recurrences. The prioritized microRNAs distinguished HRP from LRP and were associated with rate of metastatic progression and survival in an independent validation dataset. Conclusion Oligo- and poly- metastasis are distinct entities at the clinical and molecular level.

Molecular Pathways: Interferon/Stat1 Pathway: Role in the Tumor Resistance to Genotoxic Stress and Aggressive Growth

STAT1 is activated by IFNs and other cell signals. Following activation, STAT1 is translocated to the nuclei and activates transcription of IFN-stimulated genes. Although the activation of STAT1 by IFNs is classically associated with antiviral defense and tumor-suppressive functions, emerging data indicate that expression of the STAT1 pathway confers cellular resistance to DNA-damaging agents and mediates aggressive tumor growth. Recent advances in the development of Janus-activated kinase/Stat inhibitors and peptide inhibitors specific for individual Stat proteins may provide new insights into the controversial functions of this pathway. Clin Cancer Res; 18(11); 3015–21. ©2012 AACR.