Research at Cell Gitik
At Cell Gitik, we value science that ventures deep into uncharted waters and also focuses on bringing practical results in the form of effective and safe medicines. In cell biology, such ‘uncharted waters’ are linked to areas where inexplicable phenomena obstruct the integral view of a cell. Scientific findings tend to remain inexplicable if the cellular processes and components involved are considered to have no function or biological significance. An extreme example of such an unproductive decade-long view is the concept of ‘junk DNA’, a term attributed to highly repetitive sequences that constitute about half of the human genome. In fact, ‘junk DNA’ is an essential yet largely mysterious component of a cell. A portion of this ‘junk DNA’ is now known to globally control an undifferentiated state of cells in early mammalian embryos and many types of cancer, although the mechanism involved is not understood.
We are tackling this fundamental mechanism underlying the undifferentiated state of cells. The urgent necessity to address this challenge is dictated by two end-point goals. The first is to develop a highly universal anti-cancer ‘differentiation therapy’ based on understanding this mechanism and how to target it. The second is to develop a novel technology for generating induced pluripotent stem cells (iPSCs), which is expected to drastically surpass those in existence in terms of efficiency, quality of iPSCs, and clinical safety.
What we do differently:
Our research is foundational. We are focusing on creating fundamental knowledge about the undifferentiated state of cells and how it is established. Until recently, the existence of a universal mechanism(s) of undifferentiated cells had not even been questioned. Consequently, two important streams of biomedical science—the development of an anti-cancer ‘differentiation therapy’ and the reprogramming of somatic cells into pluripotent embryonic stem cells—show a lack of conceptual advances and satisfactory practical results.
Our research is unconventional. It differs from mainstream cell biology research by challenging the well-entrenched concept of the mechanism of DNA replication with respect to specific genome locations in undifferentiated embryonic and cancer cell systems.
We transcend the established disciplinary boundaries to solve these scientific and practical challenges.
The development of an anti-cancer ‘differentiation therapy’
Widely used anti-cancer chemotherapeutic drugs are toxic, and secondary cancers are a poor common outcome of such therapeutic interventions. These drugs damage not only cancer cells but also numerous normal cells, especially proliferating cells in the bone marrow and intestine. The toxicity of these drugs is largely due to the massive lysis of damaged cells and the release of their breakdown products. This is why the development of anti-cancer therapies that specifically target cancer cells but do not cause their massive destruction is a long-pursued goal.
The development of this type of therapy — a ‘differentiation therapy’— began about 40 years ago when a number of compounds were found to force acute myeloid leukemia (AML) cells to differentiate. Worldwide efforts in this direction were inspired by the highly successful treatment of the most deadly type of AML (namely, acute promyelocytic leukemia) by the administration of high doses of all-trans retinoic acid (vitamin A-like compound). This success has demonstrated that highly malignant genetically abnormal cells can be forced to differentiate, perform their function, and then can be insensibly eliminated through a programmed cell death (apoptosis) or by the host’s immune system.
However, numerous attempts to develop ‘differentiation therapies’ to cure other types of cancer have failed because they were simply empirical trials and not based on an understanding of the fundamental mechanism that controls an undifferentiated state of a cell. Nevertheless, the existence of such a mechanism is suggested by the fact that different types of cancer, being extremely diverse in terms of the involved genetic and epigenetic abnormalities, share a common feature – the lack of differentiation. Recently, it became clear that a mechanism that globally controls an undifferentiated state of a cell does exist, and it is linked to the activity of specific repetitive genomic sequences.
We are focusing on unraveling this not yet understood mechanism and selecting the most effective target within it to develop a completely new class of drug candidates for a highly universal anti-cancer ‘differentiation therapy’.
Novel approaches to reprogramming somatic cells into clinical-grade induced pluripotent stem cells
Regenerative medicine includes biomedical approaches aimed at replacing a patient’s damaged or diseased tissues with normal cells and tissues that have been engineered outside of the human body. The purpose of regenerative medicine is to restore the normal function of affected organs. The invention of a means to reprogram adult somatic differentiated cells to the pluripotent state, propagate these undifferentiated cells in culture, and then use them to produce specialized cells of essentially any type has opened a new avenue for regenerative medicine and drug discovery.
These generated pluripotent cells, termed induced pluripotent stem cells (iPSCs), resemble pluripotent embryonic stem cells (ESCs) with respect to their morphology, gene expression profiles, unlimited self-renewal capacity, and ability to differentiate into all types of specialized cells of the body. The attractiveness of potential iPSC-based regenerative therapeutic approaches is in the possibility to generate patient-specific tissues from a small number of the patient’s own cells, such as skin and blood cells.
Existing iPSC-generation technologies are based on the genetic modification of somatic cells to achieve a high expression level of four transcription factors that are thought to be key to pluripotency. However, iPSCs generated by this means are not clinically safe. The development of new iPSC-generating technologies is driven by the necessity to overcome two drawbacks of conventional iPSC generation methods: genetic modification of reprogrammed cells and extremely low efficiency.
The prospect of overcoming these issues is strongly linked to unravelling the fundamental mechanism of pluripotency, which is currently not understood. A high level of expression of several transcription factors that are conventionally used to generate iPSCs is also considered a fundamental feature associated with pluripotency. Nevertheless, it is now known that the loss of pluripotency in mouse embryogenesis occurs before the downregulation of these transcription factors, is driven by an unknown mechanism, and is associated with the establishment of an epigenetic barrier that is extremely difficult to reprogram back [1, 2]. This fact can serve as a clue for the low efficiency of conventional iPSC-generation methods and suggests incomplete reprogramming to pluripotency by existing protocols.
On the way to clinical-grade iPSCs is another issue to resolve. This issue is related to the fact that the epigenetic mechanisms underlying pluripotency and carcinogenesis have striking similarities, yet they are different in some respects. The lack of in-depth knowledge of what makes these mechanisms similar as well as different is the main roadblock to the advancement of iPSCs to clinical applications. This aspect is of the greatest importance. Any highly efficient transgene-free iPSC-generating technology has little clinical value if it does not ensure cancer-specific epigenetic mechanisms are turned off in the induced pluripotent cells.
Cell Gitik’s goal is to understand the nature of the epigenetic mechanism of pluripotency as well as its similarities to and differences from the cancer-related mechanism of an undifferentiated state. We will use that the knowledge to ensure much targeted reprogramming of somatic cells to ‘purely’ pluripotent cells not bearing any cancer-specific fingerprints. Our end-point goal in this area is the development of a highly efficient ‘organic’ (transgene-free) technology for the generation of clinical-grade iPSCs.
[1] Hiratani I. et al. Genome Res 2010, 20(2):155-169.
[2] Ryba T. et al. PLoS Comput Biol 2011, 7(10):e1002225.