Purpose: Cisplatin kills tumor cells through DNA cross linking. Alterations in the function of DNA repair genes may affect DNA repair proficiency and influence cancer patients' response to cisplatin. We studied whether single nucleotide polymorphisms (SNPs) of DNA repair genes predict the response to cisplatin or prognosis in patients with squamous cell carcinoma of the head and neck (SCCHN). Methods: A polymerase chain reaction–restriction fragment length polymorphism (RFLP) approach was used to determine the frequency of the SNPs: XPD-Asp312Asn, XPD-Lys751Gln, ERCC1-C8092A, and XRCC1-Arg399Gln in DNA from peripheral lymphocytes of 103 stage IV SCCHN patients. Results: The frequencies of the distinct genotypes were, respectively, for the homozygous common allele, heterozygous and homozygous polymorphic variant: 53%, 40%, and 7% for ERCC1; 50%, 42%, and 8% for XPD-312; 35%, 57%, and 8% for XPD751; and 35%, 51%, and 13% for XRCC1. Patients with only common alleles at all the SNPs tested had a median overall survival of 5.1 months (range, 4.3 to 6.0 months) as compared with not reached for patients with at least one polymorphic variant (P < .001). Estimates from Cox's multivariate analysis suggest that the accumulation of each polymorphic variant decreases the probability of dying by a factor of 2.1 (P < .001; the presence of seven polymorphic variants confers a 175-fold protection). The accumulation of polymorphic variants increases by 2.94-fold the probability of achieving a complete response to treatment (P = .041). Conclusion: Using a multivariate model, the presence of polymorphic variants in DNA-repair genes are powerful prognosis factors and response to cisplatin predictors among SCCHN patients.

Proteins containing a caveolin-binding domain (CBD), such as the Rho-GTPases, can interact with caveolin-1 (Cav1) through its caveolin scaffold domain. Rho-GTPases are important regulators of p130^Cas, which is crucial for both normal cell migration and Src kinase-mediated metastasis of cancer cells. However, although Rho-GTPases (particularly RhoC) and Cav1 have been linked to cancer progression and metastasis, the underlying molecular mechanisms are largely unknown. To investigate the function of Cav1–Rho-GTPase interaction in metastasis, we disrupted Cav1–Rho-GTPase binding in melanoma and mammary epithelial tumor cells by overexpressing CBD, and examined the loss-of-function of RhoC in metastatic cancer cells. Cancer cells overexpressing CBD or lacking RhoC had reduced p130^Cas phosphorylation and Rac1 activation, resulting in an inhibition of migration and invasion in vitro. The activity of Src and the activation of its downstream targets FAK, Pyk2, Ras and extracellular signal-regulated kinase (Erk)1/2 were also impaired. A reduction in α5-integrin expression, which is required for binding to fibronectin and thus cell migration and survival, was observed in CBD-expressing cells and cells lacking RhoC. As a result of these defects, CBD-expressing melanoma cells had a reduced ability to metastasize in recipient mice, and impaired extravasation and survival in secondary sites in chicken embryos. Our data indicate that interaction between Cav1 and Rho-GTPases (most likely RhoC but not RhoA) promotes metastasis by stimulating α5-integrin expression and regulating the Src-dependent activation of p130^Cas/Rac1, FAK/Pyk2 and Ras/Erk1/2 signaling cascades.

Chemokines are relevant molecules in shaping the tumor microenvironment, although their contributions to tumorigenesis are not fully understood. We studied the influence of the chemokine CX3CL1/fractalkine in de novo breast cancer formation using HER2/neu transgenic mice. CX3CL1 expression was downmodulated in HER2/neu tumors, yet, paradoxically, adenovirus-mediated CX3CL1 expression in the tumor milieu enhanced mammary tumor numbers in a dose-dependent manner. Increased tumor multiplicity was not a consequence of CX3CL1-induced metastatic dissemination of the primary tumor, although CX3CL1 induced epithelial-to-mesenchymal transition in breast cancer cells in vitro. Instead, CX3CL1 triggered cell proliferation by induction of ErbB receptors through the proteolytic shedding of an ErbB ligand. This effect was important insofar as mammary tumorigenesis was delayed and tumor multiplicity was reduced by genetic deletion of CX3CL1 in HER2/neu mice, but not in polyoma middle T-antigen oncomice. Our findings support the conclusion that CX3CL1 acts as a positive modifier of breast cancer in concert with ErbB receptors. Cancer Res; 73(14); 4461–73. ©2013 AACR.

Epithelial malignancies are effectively treated by antiangiogenics; however, acquired resistance is a major problem in cancer therapeutics. Epithelial tumors commonly have mutations in the MAPK/Pi3K-AKT pathways, which leads to high-rate aerobic glycolysis. Here, we show how multikinase inhibitor antiangiogenics (TKIs) induce hypoxia correction in spontaneous breast and lung tumor models. When this happens, the tumors downregulate glycolysis and switch to long-term reliance on mitochondrial respiration. A transcriptomic, metabolomic, and phosphoproteomic study revealed that this metabolic switch is mediated by downregulation of HIF1α and AKT and upregulation of AMPK, allowing uptake and degradation of fatty acids and ketone bodies. The switch renders mitochondrial respiration necessary for tumor survival. Agents like phenformin or ME344 induce synergistic tumor control when combined with TKIs, leading to metabolic synthetic lethality. Our study uncovers mechanistic insights in the process of tumor resistance to TKIs and may have clinical applicability.

PP2A is a major tumor suppressor whose inactivation is frequently found in a wide spectrum of human tumors. In particular, deletion or epigenetic silencing of genes encoding the B55 family of PP2A regulatory subunits is a common feature of breast cancer cells. A key player in the regulation of PP2A/B55 phosphatase complexes is the cell cycle kinase MASTL (also known as Greatwall). During cell division, inhibition of PP2A-B55 by MASTL is required to maintain the mitotic state, whereas inactivation of MASTL and PP2A reactivation is required for mitotic exit. Despite its critical role in cell cycle progression in multiple organisms, its relevance as a therapeutic target in human cancer and its dependence of PP2A activity is mostly unknown. Here we show that MASTL overexpression predicts poor survival and shows prognostic value in breast cancer patients. MASTL knockdown or knockout using RNA interference or CRISPR/Cas9 systems impairs proliferation of a subset of breast cancer cells. The proliferative function of MASTL in these tumor cells requires its kinase activity and the presence of PP2A-B55 complexes. By using a new inducible CRISPR/Cas9 system in breast cancer cells, we show that genetic ablation of MASTL displays a significant therapeutic effect in vivo. All together, these data suggest that the PP2A inhibitory kinase MASTL may have both prognostic and therapeutic value in human breast cancer.

Purpose: To characterize safety and tolerability of the selective PI3Kβ inhibitor AZD8186, identify a recommended phase II dose (RP2D), and assess preliminary efficacy in combination with abiraterone acetate or vistusertib. Patients and Methods: This phase I open-label study included patients with advanced solid tumors, particularly prostate cancer, triple-negative breast cancer, and squamous non–small cell lung cancer. The study comprised four arms: (i) AZD8186 monotherapy dose finding; (ii) monotherapy dose expansion; (iii) AZD8186/abiraterone acetate (with prednisone); and (iv) AZD8186/vistusertib. The primary endpoints were safety, tolerability, and identification of the RP2D of AZD8186 monotherapy and in combination. Secondary endpoints included pharmacokinetics (PK), pharmacodynamics, and tumor and prostate-specific antigen (PSA) responses. Results: In total, 161 patients were enrolled. AZD8186 was well tolerated across all study arms, the most common adverse events being gastrointestinal symptoms. In the monotherapy dose-finding arm, four patients experienced dose-limiting toxicities (mainly rash). AZD8186 doses of 60-mg twice daily [BID; 5 days on, 2 days off (5:2)] and 120-mg BID (continuous and 5:2 dosing) were taken into subsequent arms. The PKs of AZD8186 were dose proportional, without interactions with abiraterone acetate or vistusertib, and target inhibition was observed in plasma and tumor tissue. Monotherapy and combination therapy showed preliminary evidence of limited antitumor activity by imaging and, in prostate cancer, PSA reduction. Conclusions: AZD8186 monotherapy had an acceptable safety and tolerability profile, and combination with abiraterone acetate/prednisone or vistusertib was also tolerated. There was preliminary evidence of antitumor activity, meriting further exploration of AZD8186 in subsequent studies in PI3Kβ pathway–dependent cancers.