Preface

Cell death by endogenous and/or exogenous effects is called cytotoxicity and the effect that leads to cell death is called the cytotoxic effect. The cytotoxic effect may be physical, chemical or biological.

The basic pathway in the reality of cytotoxicity is determined by the pattern by which the cell dies. Accordingly, the cell either attempts to die in a multi-step manner in the presence of a genetically controlled mechanism, which is called apoptosis (programmed cell death), or dies by a necrosis-like mechanism ( without genetic control) that suddenly occurs for unpredictable reasons leading to inflammation.

Although not genetically controlled, some exogenous effects may also trigger apoptosis by reprogramming the genetic control of the cell-killing mechanism. There have been numerous examples of this phenomenon in practice, such as in conventional chemotherapy and radiotherapy.

The most important thing to consider at this point is, in fact, why the cell attempts to die in a controlled behaviour. This cellular death process in the organism is governed by various intrinsic purposes. One of these is the programmed destruction of a group of cells to facilitate morphogenesis during ontogenesis. Another is the pronounced cytotoxicity that takes place if the cell or subcellular compartments function insufficiently and/or are damaged.

From this perspective, *regeneration* is the reproduction of some cells that are somehow eliminated to maintain homeostasis in the organism. The first example of the use of the term regeneration in biology is seen in the example of Prometheus in Greek Mythology, who was tied to the rocks by Zeus for giving fire to the people of Mount Olympus. In this case, regeneration is observed as the constant renewal of Promethus' liver, which was fed to the eagles in order to increase the penalty. In this myth, the regeneration of the liver suggests any cell regeneration in the organism.

In any case, compensating for cytotoxicity in the multicellular organism by a certain level of cellular proliferation is the primary aim of homeostasis. In addition, the loss of cellular proliferation control (tumorigenesis) is at least as important as cytotoxicity, however, it is a contrasting trauma. With the disruption of the delicate balance between cytotoxicity and proliferation, confrontation with cancer can inevitably occur. As a result, a deep understanding of the molecular control of the mechanisms of cytotoxicity and cellular proliferation will be one of the most important perspectives in the struggle to stop cancer, the leading health problem of this century.

**II**

**Section 2**

Cytotoxicity

Methods in Cytotoxicity Assessment **85**

**Chapter 6 87**

Cell Division, Cytotoxicity, and the Assays Used in the Detection of

*by Erman Salih Istifli, Mehmet Tahir Hüsunet and Hasan Basri Ila*

We hope this book will be an important and useful resource, especially for professional researchers and students studying cytotoxicity and its control.

#### **Dr. Erman Salih Istifli and Dr. Hasan Basri Ila**

Çukurova University, Faculty of Science and Letters, Department of Biology, Adana, Turkey

**1**

Section 1

Cytotoxicity Research

## Section 1
