Julie Stakiw

Regulation of Tumor Growth and Metastasis: The Role of Tumor Microenvironment

The presence of abnormal cells with malignant potential or neoplastic characteristics is a relatively common phenomenon. The interaction of these abnormal cells with their microenvironment is essential for tumor development, protection from the body’s immune or defence mechanisms, later progression and the development of life-threatening or metastatic disease. The tumor microenvironment is a collective term that includes the tumor’s surrounding and supportive stroma, the different effectors of the immune system, blood platelets, hormones and other humoral factors. A better understanding of the interplay between the tumor cells and its microenvironment can provide efficient tools for cancer management, as well as better prevention, screening and risk assessment protocols.

Platelets Effects on Tumor Growth

Unlike other blood cells, platelets are small anucleate structures derived from marrow megakaryocytes. Thought for almost a century to possess solely hemostatic potentials, platelets, however, play a much wider role in tissue regeneration and repair and interact intimately with tumor cells. On one hand, tumor cells induce platelet aggregation (TCIPA), known to act as the trigger of cancer-associated thrombosis. On the other hand, platelets recruited to the tumor microenvironment interact, directly, with tumor cells, favoring their proliferation, and, indirectly, through the release of a wide palette of growth factors, including angiogenic and mitogenic proteins. In addition, the role of platelets is not solely confined to the primary tumor site. Indeed, they escort tumor cells, helping their intravasation, vascular migration, arrest, and extravasation to the tissues to form distant metastasis. As expected, nonspecific or specific inhibition of platelets and their content represents an attractive novel approach in the fight against cancer. This review illustrates the role played by platelets at primary tumor sites and in the various stages of the metastatic process.

Platelet-cancer interactions.

Platelets play a crucial role in the pathophysiological processes of hemostasis and thrombosis. Increasing evidence indicates that they fulfill much broader roles in balancing health and disease. The presence of tumor cells affects platelets both numerically, through a wide variety of mediators and cytokines, or functionally through tumor cell-induced platelet activation, the first step toward cancer-induced thrombosis. This induction results from signaling events through the different platelet receptors, or may be cytokine-mediated. Reciprocally, upon activation, the platelets will release a myriad of growth factors from their dense and α-granules and peroxisomes; these will directly impact tumor growth, tethering, and spread. A similar cross-talk is initiated between tumor microvesicles stimulating the platelets and platelet microparticles, promoting both thrombosis and tumor growth. A vicious loop of activation thereafter takes place. Platelets directly and indirectly promote tumor growth, and enable a molecular mimicry coating the malignant growth and allowing metastasizing cells to escape T-cell-mediated immunity and natural killer cell surveillance. Breaking this vicious activation loop with nonspecific platelet inhibitors, such as aspirin, or by targeting specific sites on the activation cascade may offer a mean to reduce both the risks of development and progression of cancer and the risk of thrombosis.

Transfusion challenges in hematology oncology and hematopoietic stem cell transplant – Literature review and local experience

Transfusion medicine plays a vital role in the supportive care of patients receiving therapy for hematology, oncology and hematopoietic stem cell transplants (HSCT). With advances in therapy with more intensive chemotherapy or radiotherapy, patients usually develop cytopenias and need frequent transfusion support with packed red blood cells, granulocyte transfusion or platelets to support them until they recover from the effect of therapy. HSCT poses unique challenges for transfusion medicine, since transplant recipients may require substantial transfusion support due to cytopenias associated with toxic medications, decreased marrow reserve, infection or their malignancy. Transfusion support has many complications, mainly immune mediated and infectious complications. Jehovahs Witness patients deny transfusions of blood products as a therapeutic option and, consequently, management of their disease with chemotherapy and stem cell transplant after myeloablative therapy is quite challenging. This review describes the challenges of transfusion support in managing hemato-oncology and stem cell transplant patients and highlights a local experience in transplanting two Jehovahs Witness patients.

A closer look at the bone marrow microenvironment in multiple myeloma

Multiple myeloma, a plasma cell (PC) neoplasm accounting for nearly 10% of hematologic malignancies, remains an incurable disease of the bone marrow (BM) with a fascinating pathophysiology. The maladaptive nature of myeloma PCs and the BM microenvironment niche has been recognized to play a crucial role in the pathogenesis and progression of the disease which behaves in a manner similar to solid tumors in their growth and dissemination. A complex interaction between osteoclasts, endothelial cells, BM matrix, myeloid as well as the lymphoid elements and the malignant PCs occurs at the level of the microenvironment favoring the expansion of latter cells and their spread. A better understanding of the diseased PC and their milieu will enable the development of novel therapeutic tools capable of improving the outcome of this incurable blood cancer.

Autologous Stem Cell Transplantation for Transformed Lymphoma: Single-Center Experience

This is a single-center review of retrospectively collected computerized data and medical records of all the patients who have undergone high dose chemotherapy and ASCT for transformed lymphoma from 1999–2014. The primary endpoint of the study was overall survival (OS) and secondary endpoint was progression free survival (PFS). A total of 27 patients with histological transformation were identified. This included transformation from follicular lymphoma Grade 1–3A and non-follicular indolent lymphoma, synchronous and asynchronous presentation. All transformed to diffuse large B cell lymphoma. 33% were chemotherapy naive prior to transformation. Median follow up was 47 months. For the entire cohort OS at 3 years was 73% and PFS = 82%. The treatment has low risk for nonrelapse mortality providing durable remission.