A possible correlation between interferon-stimulated gene expression and cytogenetic responses in chronic myelogenous leukemia patients treated with alpha-interferon

Overcoming cancer cell resistance to VSV oncolysis with JAK1/2 inhibitors

Oncolytic vesicular stomatitis virus (VSV) has potent antitumor activity but some cancer cells are resistant to VSV killing, either constitutively or due to type I interferon (IFN) inducing an antiviral state in the cells. Here, we evaluated VSV oncolysis of a panel of human head and neck cancer cells and showed that VSV resistance in SCC25 and SCC15 cells could be reversed with Janus kinase (JAK) 1/2 inhibitors (JAK inhibitor I and ruxolitinib). Pre-treatment of cells with JAK1/2 inhibitors before or in conjunction with VSV enhanced viral infection, spread and progeny yield (100- to 1000-fold increase). In contrast, inhibitors of histone deacetylase (LBH589), phosphatidylinositol 3-kinase (GDC-0941, LY294002), mammalian target of rapamycin (rapamycin) or signal transducer and activator of transcription 3 (STAT3 inhibitor VII) were ineffective. Compared with VSV-sensitive SW579 cells, IFNα/β responsive antiviral genes (IRF-9, IRF-7, OAS1 but not MxA) are constitutively expressed in SCC25 cells. Pretreatment with JAK inhibitors reduced mRNA levels of these genes, increasing VSV expression in the cells. Interestingly, 1 h of drug exposure was sufficient to reverse SCC25 resistance to VSV and was still effective if virus was added 24 h later. Overall, we show here that JAK inhibitor I and ruxolitinib (Jakafi) can reverse resistance to VSV, supporting the rationale to incorporate JAK1/2 inhibitors in future VSV virotherapy trials.

BRCA1 regulates the interferon gamma-mediated apoptotic response

BRCA1 is a tumor suppressor gene implicated in transcriptional regulation. We have generated cell lines with inducible expression of BRCA1 as a tool to identify downstream targets that may be important mediators of BRCA1 function. Oligonucleotide array-based expression profiling identified 11 previously described interferon regulated genes that were up-regulated following inducible expression of BRCA1. Northern blot analysis revealed that a subset of the identified targets including IRF-7, MxA, and ISG-54 were synergistically up-regulated by BRCA1 in the presence of interferon gamma (IFN-gamma) but not interferons alpha or beta. Importantly, IFN-gamma-mediated induction of IRF-7 and MxA was attenuated in the BRCA1 mutant cell line HCC1937, an effect that was rescued following reconstitution of exogenous wild type BRCA1 in these cells. Furthermore, reconstituted BRCA1 sensitized HCC1937 cells to IFN-gamma-induced apoptotic cell death. This study identifies BRCA1 as a component of the IFN-gamma-regulated signaling pathway and suggests that BRCA1 may play a role in the regulation of IFN-gamma-mediated apoptosis.

The relationship between telomere length and therapy-associated cytogenetic responses in patients with chronic myeloid leukemia

BACKGROUND

Chronic myeloid leukemia (CML) is a clonal disease with specific cytogenetic changes involving the Philadelphia (Ph) translocation. The authors examined the relationship between telomere length (terminal restriction fragment [TRF]) and therapy-associated cytogenetic responses in CML patients.

METHODS

The authors examined the telomere length and telomerase activity in 44 patients with Ph-positive CML in the chronic phase. TRF was determined by Southern blot analysis using the (TTAGGG)4 probe and telomerase activity was assessed by the telomeric repeat amplification protocol and fluorescent-labeled primers.

RESULTS

At the time of CML diagnosis, 19 patients had TRFs within the age-matched normal range (mean +/- 2 x standard deviation [SD]) and the remaining 25 patients had TRFs shorter than the age-matched normal range (< mean +/- 2 x SD). Hematologic findings, including leukocyte count, hemoglobin level, platelet count, and percentage of bone marrow blasts at the time of diagnosis did not significantly differ between patients with normal and shortened TRFs; however, those with shortened TRFs had high levels of telomerase activity (P = 0.045). In a group of patients treated with alpha-interferon (n = 32), those with normal TRFs had a significantly lower frequency of blast crises (P = 0.0328), a significantly higher incidence of cytogenetic responses (P = 0.0185), and a favorable prognosis (P < 0.01) compared with those with shortened TRFs.

CONCLUSIONS

These findings suggest that normal TRFs in a small number of CML patients at the time of diagnosis may have a significant amount of normal stem cells remaining. The authors suggest that normal TRFs at the time of diagnosis indicate a subset of CML patients who may respond favorably to alpha-interferon therapy.