Non‐invasive sensitive detection of KRAS and BRAF mutation in circulating tumor cells of colorectal cancer patients

Characterization of genetic alterations in tumor biopsies serves as useful biomarkers in prognosis and treatment management. Circulating tumor cells (CTCs) obtained non‐invasively from peripheral blood could serve as a tumor proxy. Using a label‐free CTC enrichment strategy that we have established, we aimed to develop sensitive assays for qualitative assessment of tumor genotype in patients. Blood consecutively obtained from 44 patients with local and advanced colorectal cancer and 18 healthy donors were enriched for CTCs using a size‐based microsieve technology. To screen for CTC mutations, we established high‐resolution melt (HRM) and allele‐specific PCR (ASPCR) KRAS‐codon 12/13‐ and BRAF‐codon 600‐ specific assays, and compared the performance with pyrosequencing and Sanger sequencing. For each patient, the resulting CTC genotypes were compared with matched tumor and normal tissues. Both HRM and ASPCR could detect as low as 1.25% KRAS‐ or BRAF‐mutant alleles. HRM detected 14/44 (31.8%) patients with KRAS mutation in CTCs and 5/44 (11.3%) patients having BRAF mutation in CTCs. ASPCR detected KRAS and BRAF mutations in CTCs of 10/44 (22.7%) and 1/44 (2.3%) patients respectively. There was an increased detection of mutation in blood using these two methods. Comparing tumor tissues and CTCs mutation status using HRM, we observed 84.1% concordance in KRAS genotype (p = 0.000129, Fishers'' exact test; OR = 38.7, 95% CI = 4.05–369) and 90.9% (p = 0.174) concordance in BRAF genotype. Our results demonstrate that CTC enrichment, coupled with sensitive mutation detection methods, may allow rapid, sensitive and non‐invasive assessment of tumor genotype.     

Inhibition of PARP1‐dependent end‐joining contributes to Olaparib‐mediated radiosensitization in tumor cells

Poly‐ADP‐ribose‐polymerase inhibitors (PARPi) are considered to be optimal tools for specifically enhancing radiosensitivity. This effect has been shown to be replication‐dependent and more profound in HR‐deficient tumors. Here, we present a new mode of PARPi‐mediated radiosensitization which was observed in four out of six HR‐proficient tumor cell lines (responders) investigated, but not in normal cells. This effect is replication‐independent, as the radiosensitization remained unaffected following the inhibition of replication using aphidicolin. We showed that responders are radiosensitized by Olaparib because their DSB‐repair is switched to PARP1‐dependent end‐joining (PARP1‐EJ), as evident by (i) the significant increase in the number of residual γH2AX foci following irradiation with 3Gy and treatment with Olaparib, (ii) the enhanced enrichment of PARP1 at the chromatin after 3Gy and (iii) the inhibition of end‐joining activity measured by a specific reporter substrate upon Olaparib treatment. This is the first study which directly demonstrates the switch to PARP1‐EJ in tumor cells and its contribution to the response to Olaparib as a radiosensitizer, findings which could widen the scope of application of PARPi in tumor therapy.     

Treatment-emergent mutations in NAEβ confer resistance to the NEDD8-activating enzyme inhibitor MLN4924

MLN4924 is an investigational small-molecule inhibitor of NEDD8-activating enzyme (NAE) in clinical trials for the treatment of cancer. MLN4924 is a mechanism-based inhibitor, with enzyme inhibition occurring through the formation of a tight-binding NEDD8-MLN4924 adduct. In cell and xenograft models of cancer, we identified treatment-emergent heterozygous mutations in the adenosine triphosphate binding pocket and NEDD8-binding cleft of NAEβ as the primary mechanism of resistance to MLN4924. Biochemical analyses of NAEβ mutants revealed slower rates of adduct formation and reduced adduct affinity for the mutant enzymes. A compound with tighter binding properties was able to potently inhibit mutant enzymes in cells. These data provide rationales for patient selection and the development of next-generation NAE inhibitors designed to overcome treatment-emergent NAEβ mutations.     

Targeting MYCN IRES in MYCN‐amplified neuroblastoma with miR‐375 inhibits tumor growth and sensitizes tumor cells to radiation

The MYCN oncogene is amplified in 20% of neuroblastomas, leading to its overexpression at both the mRNA and protein levels. MYCN overexpression is strongly associated with advanced disease stage, rapid tumor progression and a worse prognosis. In the present study, we identified microRNA‐375 (miR‐375) as a negative regulator of MYCN: enforced expression of miR‐375 inhibited MYCN‐amplified neuroblastoma in vitro and in vivo. Upon searching the website miRbase for possible miR‐375 binding sites within the whole MYCN mRNA, we found that the MYCN 5′‐UTR had significant sequence complementarity to miR‐375, yet no complementary sequences existed within the MYCN 3′‐UTR and coding regions. Enforced overexpression of miR‐375 efficiently inhibited MYCN mRNA translation and protein synthesis, via an IRES‐dependent mechanism. In athymic nude mouse model with human MYCN‐amplified neuroblastoma, MYCN downregulation by miR‐375 led to inhibition of tumor cell growth and tumorigenicity. In particular, miR‐375‐regulated inhibition of MYCN translation was enhanced when MYCN‐amplified neuroblastoma cells were exposed to stress stimulation, such as ionizing irradiation (IR), resulting in a remarkable increase in the neuroblastoma''s sensitivity to IR‐induced cell death. Our results identified a novel mechanism by which IRES‐dependent translation of MYCN is repressed by miR‐375, particularly during cellular stress, highlighting a potential anticancer strategy: the development of miR‐375 as a novel therapeutic agent to treat MYCN‐amplified neuroblastoma.     

Evaluating near-infrared photoimmunotherapy for targeting fibroblast activation protein-α expressing cells in vitro and in vivo

Photoimmunotherapy (PIT), carried out using an Ab conjugated to the near infrared dye IRDye700DX, is achieving significant success in target-specific elimination of cells. Fibroblast activation protein alpha (FAP-α) is an important target in cancer because of its expression by cancer-associated fibroblasts (CAFs) as well as by some cancer cells. Cancer-associated fibroblasts that express FAP-α have protumorigenic and immune suppressive functions. Using immunohistochemistry of human breast cancer tissue microarrays, we identified an increase of FAP-α⁺ CAFs in invasive breast cancer tissue compared to adjacent normal tissue. We found FAP-α expression increased in fibroblasts cocultured with cancer cells. In proof-of-principle studies, we engineered human FAP-α overexpressing MDA-MB-231 and HT-1080 cancer cells and murine FAP-α overexpressing NIH-3T3 fibroblasts to evaluate several anti-FAP-α Abs and selected AF3715 based on its high binding affinity with both human and mouse FAP-α. After conjugation of AF3715 with the phthalocyanine dye IR700, the resultant Ab conjugate, FAP-α-IR700, was evaluated in cells and tumors for its specificity and effectiveness in eliminating FAP-α expressing cell populations with PIT. Fibroblast activation protein-α-IR700-PIT resulted in effective FAP-α-specific cell killing in the engineered cancer cells and in two patient-derived CAFs in a dose-dependent manner. Following an intravenous injection, FAP-α-IR700 retention was three-fold higher than IgG-IR700 in FAP-α overexpressing tumors, and two-fold higher compared to WT tumors. Fibroblast activation protein-α-IR700-PIT resulted in significant growth inhibition of tumors derived from FAP-α overexpressing human cancer cells. A reduction of endogenous FAP-α⁺ murine CAFs was identified at 7 days after FAP-α-IR700-PIT. Fibroblast activation protein-α-targeted near infrared PIT presents a promising strategy to eliminate FAP-α⁺ CAFs.     

Effect of human skin-derived stem cells on vessel architecture, tumor growth, and tumor invasion in brain tumor animal models

Glioblastomas represent an important cause of cancer-related mortality with poor survival. Despite many advances, the mean survival time has not significantly improved in the last decades. New experimental approaches have shown tumor regression after the grafting of neural stem cells and human mesenchymal stem cells into experimental intracranial gliomas of adult rodents. However, the cell source seems to be an important limitation for autologous transplantation in ghoblastoma. In the present study, we evaluated the tumor targeting and antitumor activity of human skin--derived stem cells （hSDSCs） in human brain tumor models. The hSDSCs exhibit tumor targeting characteristics in vivo when injected into the controlateral hemisphere or into the tail vein of mice. When implanted directly into glioblastomas, hSDSCs distributed themselves extensively throughout the tumor mass, reduced tumor vessel density, and decreased anglogenic sprouts.In addition, transplanted hSDSCs differentiate into pericyte cell and release high amounts of human transforming growth factor-betal with low expression of vascular endothehal growth factor, which may contribute to the decreased tumor cell invasion and number of tumor vessels.     

Response and resistance to NF-κB inhibitors in mouse models of lung adenocarcinoma

Lung adenocarcinoma is a leading cause of cancer death worldwide. We recently showed that genetic inhibition of the NF-κB pathway affects both the initiation and the maintenance of lung cancer, identifying this pathway as a promising therapeutic target. In this investigation, we tested the efficacy of small-molecule NF-κB inhibitors in mouse models of lung cancer. In murine lung adenocarcinoma cell lines with high NF-κB activity, the proteasome inhibitor bortezomib efficiently reduced nuclear p65, repressed NF-κB target genes, and rapidly induced apoptosis. Bortezomib also induced lung tumor regression and prolonged survival in tumor-bearing Kras(LSL-G12D/wt);p53(flox/flox) mice but not in Kras(LSL-G12D/wt) mice. After repeated treatment, initially sensitive lung tumors became resistant to bortezomib. A second NF-κB inhibitor, Bay-117082, showed similar therapeutic efficacy and acquired resistance in mice. Our results using preclinical mouse models support the NF-κB pathway as a potential therapeutic target for a defined subset of lung adenocarcinoma. SIGNIFICANCE: Using small-molecule compounds that inhibit NF-κB activity, we provide evidence that NF-κB inhibition has therapeutic efficacy in the treatment of lung cancer. Our results also illustrate the value of mouse models in validating new drug targets in vivo and indicate that acquired chemoresistance may later influence bortezomib treatment in lung cancer.     

Sialyl Tn‐expressing bladder cancer cells induce a tolerogenic phenotype in innate and adaptive immune cells

Despite the wide acceptance that glycans are centrally implicated in immunity, exactly how they contribute to the tilt immune response remains poorly defined. In this study, we sought to evaluate the impact of the malignant phenotype‐associated glycan, sialyl‐Tn (STn) in the function of the key orchestrators of the immune response, the dendritic cells (DCs). In high grade bladder cancer tissue, the STn antigen is significantly overexpressed and correlated with the increased expression of ST6GALNAC1 sialyltransferase. Bladder cancer tissue presenting elevated expression of ST6GALNAC1 showed a correlation with increased expression of CD1a, a marker for bladder immature DCs and showed concomitant low levels of Th1‐inducing cytokines IL‐12 and TNF‐α. In vitro, human DCs co‐incubated with STn+ bladder cancer cells, had an immature phenotype (MHC‐II^low, CD80^low and CD86^low) and were unresponsive to further maturation stimuli. When contacting with STn⁺ cancer cells, DCs expressed significantly less IL‐12 and TNF‐α. Consistent with a tolerogenic DC profile, T cells that were primed by DCs pulsed with antigens derived from STn⁺ cancer cells were not activated and showed a FoxP3^high IFN‐γ^low phenotype. Blockade of STn antigens and of STn⁺ glycoprotein, CD44 and MUC1, in STn⁺ cancer cells was able to lower the induction of tolerance and DCs become more mature.Overall, our data suggest that STn‐expressing cancer cells impair DC maturation and endow DCs with a tolerogenic function, limiting their capacity to trigger protective anti‐tumour T cell responses. STn antigens and, in particular, STn⁺ glycoproteins are potential targets for circumventing tumour‐induced tolerogenic mechanisms.     

Genetic depletion and pharmacological targeting of αv integrin in breast cancer cells impairs metastasis in zebrafish and mouse xenograft models

Introduction

Increased expression of αv integrins is frequently associated with tumor cell adhesion, migration, invasion and metastasis, and correlates with poor prognosis in breast cancer. However, the mechanism by which αv integrins can enhance breast cancer progression is still largely unclear. The effects of therapeutic targeting of αv integrins in breast cancer also have yet to be investigated.

Methods

We knocked down αv integrin in MDA-MB-231 and MCF10A-M4 breast cancer cells, or treated these cells with the αv antagonist GLPG0187. The effects of αv integrin depletion on mesenchymal markers, transforming growth factor-β (TGF-β)/Smad signaling and TGF-β-induced target gene expression were analyzed in MDA-MB-231 cells by RNA analysis or Western blotting. The function of αv integrin on breast cancer cell migration was investigated by transwell assay in vitro, and its effect on breast cancer progression was assessed by both zebrafish and mouse xenografts in vivo. In the mouse model, GLPG0187 was administered separately, or in combination with the standard-of-care anti-resorptive agent zoledronate and the chemotherapeutic drug paclitaxel, to study the effects of combinational treatments on breast cancer metastasis.

Results

Genetic interference and pharmacological targeting of αv integrin with GLPG0187 in different breast cancer cell lines inhibited invasion and metastasis in the zebrafish or mouse xenograft model. Depletion of αv integrin in MDA-MB-231 cells inhibited the expression of mesenchymal markers and the TGF-β/Smad response. TGF-β induced αv integrin mRNA expression and αv integrin was required for TGF-β-induced breast cancer cell migration. Moreover, treatment of MDA-MB-231 cells with non-peptide RGD antagonist GLPG0187 decreased TGF-β signaling. In the mouse xenografts GLPG0187 inhibited the progression of bone metastasis. Maximum efficacy of inhibition of bone metastasis was achieved when GLPG0187 was combined with the standard-of-care metastatic breast cancer treatments.

Conclusion

These findings show that αv integrin is required for efficient TGF-β/Smad signaling and TGF-β-induced breast cancer cell migration, and for maintaining a mesenchymal phenotype of the breast cancer cells. Our results also provide evidence that targeting αv integrin could be an effective therapeutic approach for treatment of breast cancer tumors and/or metastases that overexpress αv integrin.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-015-0537-8) contains supplementary material, which is available to authorized users.     

Class III ��-tubulin expression and in vitro resistance to microtubule targeting agents

Background:

Class III β-tubulin overexpression is a marker of resistance to microtubule disruptors in vitro, in vivo and in the clinic for many cancers, including breast cancer. The aims of this study were to develop a new model of class III β-tubulin expression, avoiding the toxicity associated with chronic overexpression of class III β-tubulin, and study the efficacy of a panel of clinical and pre-clinical drugs in this model.

Methods:

MCF-7 (ER+ve) and MDA-MB-231 (ER−ve) were either transfected with pALTER-TUBB3 or siRNA-tubb3 and 24 h later exposed to test compounds for a further 96 h for proliferation studies. RT–PCR and immunoblotting were used to monitor the changes in class III β-tubulin mRNA and protein expression.

Results:

The model allowed for subtle changes in class III β-tubulin expression to be achieved, which had no direct effect on the viability of the cells. Class III β-tubulin overexpression conferred resistance to paclitaxel and vinorelbine, whereas downregulation of class III β-tubulin rendered cells more sensitive to these two drugs. The efficacy of the colchicine-site binding agents, 2-MeOE2, colchicine, STX140, ENMD1198 and STX243 was unaffected by the changes in class III β-tubulin expression.

Conclusion:

These data indicate that the effect of class III β-tubulin overexpression may depend on where the drug''s binding site is located on the tubulin. Therefore, this study highlights for the first time the potential key role of targeting the colchicine-binding site, to develop new treatment modalities for taxane-refractory breast cancer.     

Synergistic effects of genetically engineered stem cells expressing cytosine deaminase and interferon-β via their tumor tropism to selectively target human hepatocarcinoma cells

Stem cells have received a great deal of attention for their clinical and therapeutic potential for treating human diseases and disorders. Recent studies have shown that it is possible to genetically engineered stem cells (GESTECs) to produce suicide enzymes that convert non-toxic prodrugs to toxic metabolites, selectively migrate toward tumor sites and reduce tumor growth. In this study, we evaluated whether these GESTECs are capable of migrating to hepatocarcinoma cells and examined the potential therapeutic efficacy of gene-directed enzyme prodrug therapy against liver cancer cells in cellular and animal models. A modified transwell migration assay was performed to determine the migratory capacity of GESTECs to Hep3B hepatocarcinoma cells. GESTECs, that is, HB1.F3.CD or HB1.F3.CD.interferon-β (IFN-β) cells, engineered to express a suicide gene, cytosine deaminase (CD), selectively migrated toward liver cancer cells. Treatment of Hep3B, human liver cancer cells, with the prodrug 5-fluorocytosine (5-FC) in the presence of HB1.F3.CD or HB1.F3.CD.IFN-β cells resulted in the inhibition of Hep3B cell growth. In a xenografted mouse model injected with hepatocarcinoma, we investigated the therapeutic effect of these stem cells. For 9 weeks, the xenografted mice were treated with HB1.F3.CD or HB1.F3.CD.IFN-β in the presence of 5-FC. A growth of tumor mass was inhibited about 40-50% in the mice treated with GESTECs and a prodrug. In addition, we further confirmed the cytotoxic effect on tumor cells by histological analysis and migratory effect of therapeutic stem cells. Taken together, GESTECs expressing a fusion gene encoding CD and IFN-β may exert a synergistic antitumor effect on this type of tumor.     

Nimbolide targets BCL2 and induces apoptosis in preclinical models of Waldenstr?ms macroglobulinemia

Neem leaf extract (NLE) has medicinal properties, which have been attributed to its limonoid content. We identified the NLE tetranorterpenoid, nimbolide, as being the key limonoid responsible for the cytotoxicity of NLE in various preclinical models of human B-lymphocyte cancer. Of the models tested, Waldenströms macroglobulinemia (WM) cells were most sensitive to nimbolide, undergoing significant mitochondrial mediated apoptosis. Notably, nimbolide toxicity was also observed in drug-resistant (bortezomib or ibrutinib) WM cells. To identify putative targets of nimbolide, relevant in WM, we used chemoinformatics-based approaches comprised of virtual in silico screening, molecular modeling and target–ligand reverse docking. In silico analysis revealed the antiapoptotic protein BCL2 was the preferential binding partner of nimbolide. The significance of this finding was further tested in vitro in RS4;11 (BCL2-dependent) tumor cells, in which nimbolide induced significantly more apoptosis compared with BCL2 mutated (Jurkat BCL2^Ser70-Ala) cells. Lastly, intraperitoneal administration of nimbolide in WM tumor xenografted mice, significantly reduced tumor growth and IgM secretion in vivo, while modulating the expression of several proteins as seen on immunohistochemistry. Overall, our data demonstrate that nimbolide is highly active in WM cells, as well as other B-cell cancers, and engages BCL2 to exert its cytotoxic activity.     

Responses of human glioblastoma cells to human natural tumor necrosis factor-α: Susceptibility,mechanism of resistance and cytokine production studies

Summary Responses and susceptibility of 14 human glioblastoma cell lines to human natural tumor necrosis factor- (TNF) were studiedin vitro.Susceptibility of glioblastoma cells to TNF varied in experimental conditions applied. Most of glioblastoma cell lines were resistant to cytotoxic activity of TNF in a MTT assay at concentrations below 16U/ml for 72 h exposure. However, TNF at higher dose, in prolonged exposure and against low density of target cells was antiproliferative for certain glioblastoma cultures. TNF exposure at 10U/ml for 48 h suppressed DNA synthesis in 9 of 14 glioblastoma cultures, but increased in 3 cultures. In addition, colony forming assay showed anti-clonogenic activity of TNF in 5 of 6 glioblastoma cell lines tested.In spite of their low susceptibility to TNF, glioblastoma cells well responded to TNF stimulation at low dose (10U/ml) for a short period in the absence of cell damage. Productions of Interleukin-6 (IL-6), IL-8-like activity, granulocyte-macrophage colony stimulating factor (GM-CSF), prostaglandin E₂ (PGE₂) and manganous Superoxide dismutase (Mn-SOD) were enhanced or induced by the low-dose TNF stimulation.Mn-SOD, a protein protective against oxidative cell damage, was well induced in time- and dose-dependent manner, however did not correlate with TNF resistance. Whereas the levels of PGE₂ in TNF-susceptible cell lines, H-4 and SF-188, were higher than those of other lines.In conclusion, most of glioblastoma cells are resistant to TNF cytotoxic effects, but highly responsive to TNF stimulation. Its effect on glioblastoma cells appears to modulate cell differentiation rather than to kill the cells.     

A novel small‐molecule activator of procaspase‐3 induces apoptosis in cancer cells and reduces tumor growth in human breast,liver and gallbladder cancer xenografts

Purpose

Procaspase‐3, a proenzyme of apoptotic executioner caspase‐3, is overexpressed in numerous tumors. We aimed to characterize a novel procaspase‐3 activator, WF‐210, which may have potential as an anticancer drug.

Experimental design

The procaspase‐3 activating ability, antitumor efficacy, mechanisms of action, and toxicity profiles of WF‐210 were investigated in vitro and in vivo, using normal cells, cancer cells, and mouse xenograft models. The role of procaspase‐3 in WF‐210‐induced apoptosis was explored by manipulating procaspase‐3 expression in cultured cells.

Results

WF‐210 activated procaspase‐3 with an EC50 of 0.95 μM, less than half that of its mother compound PAC‐1 (2.08 μM). The mechanism involved the chelation of inhibitory zinc ions, subsequently resulting in an auto‐activation of procaspase‐3. WF‐210 was more cytotoxic than PAC‐1 to human cancer cells, but less cytotoxic to normal cells. Cancer cells with high procaspase‐3 expression, like HL‐60 and U‐937, were particularly sensitive. WF‐210‐induced the apoptosis of HL‐60 and U‐937 cells by activating procaspases and promoting proteasome‐dependent degradation of XIAP and Survivin. The level of WF‐210‐induced apoptosis in cultured cells was related to the level of procaspase‐3 expression. Finally, WF‐210 was superior to PAC‐1 in retarding the in vivo growth of breast, liver and gallbladder xenograft tumors which overexpress procaspase‐3, and induced no substantial weight loss or neurotoxicity. WF‐210 and PAC‐1 had no effect on the growth of MCF‐7 xenograft tumors, which do not express procaspase‐3.

Conclusion

We identified WF‐210 as a potent small‐molecule activator of procaspase‐3. The favorable antitumor activity and acceptable toxicity profile of WF‐210 provide a strong rationale for its clinical evaluation in the treatment of tumors with high procaspase‐3 expression.     

An ‘in‐cell trial’ to assess the efficacy of a monovalent anti‐MET antibody as monotherapy and in association with standard cytotoxics

In clinical practice, targeted therapies are usually administered together with chemotherapeutics. However, little is known whether conventional cytotoxic agents enhance the efficacy of targeted compounds, and whether a possible synergy would be dictated by drug‐sensitizing genetic alterations. To explore these issues, we leveraged the design of clinical studies in humans to conduct a multi‐arm trial in an ‘in‐cell’ format. Using the MET oncogene as a model target and a panel of genetically characterized cell lines as a reference population, we found that two different chemotherapeutic regimens – cisplatin and 5‐fluorouracil – exerted widespread cytotoxic activity that was not further enhanced by MET inhibition with a monovalent anti‐MET antibody. From a complementary perspective, targeted MET inhibition was successful in a selected complement of cells harboring MET genomic lesions. In this latter setting, addition of chemotherapy did not provide a therapeutic advantage. Mechanistically, chemotherapeutics did not influence the basal activity of MET in cells with normal MET genomic status nor did they contribute to neutralize MET signals in cells with MET amplification. These data suggest that tumors displaying MET aberrations achieve plateau responses by MET monotherapy and do not receive further benefit by addition of cytotoxic treatments.     

CCL21-Ser expression in melanoma cells recruits CCR7+ naïve T cells to tumor tissues and promotes tumor growth

CCL21-Ser, a chemokine encoded by the Ccl21a gene, is constitutively expressed in the thymic epithelial cells and stromal cells of secondary lymphoid organs. It regulates immune cell migration and survival through its receptor CCR7. Herein, using CCL21-Ser-expressing melanoma cells and the Ccl21a-deficient mice, we demonstrated the functional role of cancer cell-derived CCL21-Ser in melanoma growth in vivo. The B16-F10 tumor growth was significantly decreased in Ccl21a-deficient mice compared with that in wild-type mice, indicating that host-derived CCL21-Ser contributes to melanoma proliferation in vivo. In Ccl21a-deficient mice, tumor growth of melanoma cells expressing CCL21-Ser was significantly enhanced, suggesting that CCL21-Ser from melanoma cells promotes tumor growth in the absence of host-derived CCL21-Ser. The increase in tumor growth was associated with an increase in the CCR7⁺ CD62L⁺ T cell frequency in the tumor tissue but was inversely correlated with Treg frequency, suggesting that naïve T cells primarily promote tumor growth. Adoptive transfer experiments demonstrated that naïve T cells are preferentially recruited from the blood into tumors with melanoma cell-derived CCL21-Ser expression. These results suggest that CCL21-Ser from melanoma cells promotes the infiltration of CCR7⁺ naïve T cells into the tumor tissues and creates a tumor microenvironment favorable for melanoma growth.     

p53 mutations and resistance to chemotherapy: a stab in the back for p73?

p53 gene is a member of a multigene family that includes p53, p63 and p73. The association of p73 and p63 with cell transformation has been elusive as no genetic or epigenetic alteration of these genes has been uncovered yet. Recent work has shown clearly that p73 is an essential component of the signaling pathway that lead to apoptosis after DNA damage induced by cytotoxic agents use in cancer therapy. Furthermore, it has been established that a sub-category of mutant p53 is able to interact with p73 and inhibit its apoptotic activity. Such discovery will be important for a better understanding of the signaling pathway that lead to resistance to chemotherapy.