News from the journal clinical examination: March 23, 2011

TITLE: Mouse and human neutrophils induce anaphylaxis

Accompanying commentary:
TITLE: Neutrophils give us a shock

ONCOLOGY
Going to the ends of the chromosomes to understand cancer

Each time a cell divides, the ends of the chromosomes (telomeres) shorten slightly, and this process naturally limits the number of times a cell can replicate. The uncontrolled growth of cancer is often characterized by activation of telomerase, which lengthens telomeres and helps cells escape this replication roadblock. How telomerase is activated in cancer cells and controlled in healthy cells is not completely understood.

In this paper, Kun Ping Lu and colleagues, at Beth Israel Deaconess Medical Center in Boston, Massachusetts, demonstrate that a gene that lies in a genomic region frequently deleted in tumors called PinX1 is a negative regulator of telomerase. They found that PinX1 expression was decreased in cancer cell lines and tissues, and mice with reduced levels of PinX1 develop spontaneous tumors. The authors believe that these findings suggest that PinX1 acts as a tumor suppressor, and intuit that inhibition of telomerase might be an effective therapy in patients with PinX1 related cancers. In the accompanying commentary, Brad Johnson, of the University of Pennsylvania in Philadelphia, explains that the findings in current study may also reveal new insights into the interplay of telomere biology, chromosome stability, and cancer initiation.

TITLE: The telomerase inhibitor PinX1 is a major haploinsufficient tumor suppressor

ACCOMPANYING COMMENTARY
TITLE: PinX1 the tail on the chromosome

IMMUNOLOGY
Learning how to out-Fox tumor tolerance

Tumor growth is supported, in part, by populations of suppressive immune cells which inhibit anti-tumor T cell activation. Identifying the cell populations that promote T cell tolerance could help researchers target this process and improve the efficacy of cancer vaccines. Dendritic cells (DCs) are known to induce T cell tolerance, but the signals and factors that control this process are not completely understood.

In this paper, Arthur Hurwitz and colleagues, at the National Cancer Institute in Frederick, Maryland demonstrate that in human and mouse prostate cancers, the ability of DCs to suppress immune responses requires expression of the transcription factor Foxo3. Furthermore, they found a subpopulation of DCs that could directly convert T cells to a tolerogenic state. In the accompanying commentary, Vincenzo Bronte, of Verona University Hospital in Verona, Italy, suggests that Foxo3 may be a promising target in the design of new cancer therapeutics, but points out that there is likely a network of factors and signaling pathways that all contribute to promoting tolerance, and successful immunotherapy might require simultaneous targeting of multiple molecules.

TITLE: FOXO3 programs tumor-associated DCs to become tolerogenic in human and murine prostate cancer

ONCOLOGY
How cancer cells find their niche

Cancers that form in one part of the body can spread and invade other tissues, a process known as metastasis. Bone is a common site of metastasis for certain types of cancer, however, it is unclear how and why tumor cells re-locate specifically to the bone.

In new research, Russell S. Taichman and colleagues, of the University of Michigan School of Dentistry in Ann Arbor, Michigan, used a mouse model to demonstrate that metastatic prostate cancer cells move to the bone marrow by following the same signals used by hematopoietic stem cells. Indeed, the two populations compete to occupy the stem cell niche, and drugs that mobilize hematopoietic stem cells out of the bone marrow also mobilize metastatic cancer cells. In the accompanying commentary, Laura Schuettpelz and Daniel Link, of Washington University School of Medicine, Saint Louis, Missouri, point out that these findings suggest that the conditions of the niche may be what make metastatic bone cancers resistant to chemotherapy, and that disrupting the cancer cell-niche interaction might improve therapeutic efficacy.

TITLE: Human prostate cancer metastases target the hematopoietic stem cell niche to establish footholds in mouse bone marrow

ACCOMPANYING COMMENTARY
TITLE: Niche competition and cancer metastasis to bone

ONCOLOGY
Stromal cells put up a fight

As tumors grow in size, they require a continuous supply of nutrients and oxygen, supplied by the growth of new blood vessels. Thus, multiple cancer therapeutics that target this pathway (called anti-angiogenics) are currently in use, most of which block signaling through the vascular endothelial growth factor receptor (VEGFR). However, not all patients respond to anti-angiogenic therapy, and even in those that have initial favorable responses, resistance to these drugs inevitably develops. The cellular mechanisms that explain this resistance are not well understood; indeed, it remains unclear whether the resistance occurs due to changes in the tumor cells themselves, or in the surrounding stromal cells.

In this paper, John Heymach and colleagues, at the M. D. Anderson Cancer Center in Houston, Texas, investigated three different models of non small cell lung cancer (NSCLC), and found that resistance to anti-angiogenics developed when stromal cells increased expression of an alternative pro-angiogenic molecule, endothelial growth factor receptor (EGFR). Furthermore, the researchers demonstrated differences in the types of cells that express EGFR depending on whether the model displayed intrinsic or developed resistance to therapy. In the accompanying commentary, Oriol Casanovas of the Catalan Institute of Oncology in Barcelona, Spain, stresses that these findings may be very clinically relevant, and that therapies that combine inhibition of more than one angiogenic pathway might be useful in circumventing resistance.

TITLE: Upregulated stromal EGFR and vascular remodeling in mouse xenograft models of angiogenesis inhibitor-resistant human lung adenocarcinoma

ACCOMPANYING COMMENTARY
TITLE: The adaptive stroma joining the antiangiogenic resistance front

ONCOLOGY
Genome sequencing identifies a critical pathway in leukemia

Acute promyelocytic leukemia (APL) is a cancer of the bone marrow that accounts for approximately 1% of pediatric leukemias. APL has been linked to a specific genetic event called a translocation; a fusion between chromosomes 15 and 17 that generates a novel protein thought to be responsible for the cancerous cell growth. However, APL patients are known to have additional chromosomal alterations, and the slow progression of mouse models of the disease suggest that there may be additional mutations that cooperate with the translocation event to promote oncogenesis.

In this paper, Richard Wilson and colleagues, at Washington University in St. Louis, Missouri, describe a new method of sequencing the genome of a mouse model of APL to identify the secondary mutations that allow the cancer to progress. In particular, they identified a mutation in the Jak1 gene, part of an intracellular signaling pathway that regulates growth. In combination with the initiating translocation, this Jak1 mutation led to rapid disease progression in mice. In the accompanying commentary, Raajit Rampal and Ross Levine of Memorial Sloan-Kettering Cancer Center, in New York, New York point out that these data suggest there may be a previously unidentified role for the JAK pathway in the progression of APL that could represent a new therapeutic target. In addition, they believe that this innovative genome sequencing method could be applied to mouse models to uncover the underlying genetic causes of other human diseases.

TITLE:Sequencing a mouse acute promyelocytic leukemia genome reveals genetic events relevant for disease progression

ACCOMPANYING COMMENTARY
TITLE: Finding a needle in a haystack: whole genome sequencing and mutation discovery in murine models

Source:
Kathryn Claiborn
Journal of Clinical Investigation