environment includes the tissue context located at the vicinity of the tumor
(sometimes called the tumor microenvironment), but also elements located
quite remotely from the tumor in the organism (such as some immune-
associated organs and the microbiota, which recently has been proven to
influence cancer progression and therapies) (Zitvogel et al. 2018; Binnewies
et al. 2018; Laplane et al. 2018). Even authors who initially focused on
intrinsic molecular aspects of cancer development have later emphasized the
importance of the tumor microenvironment (Hanahan and Weinberg 2011).
Targeting the tumor microenvironment also offers enriched therapeutic stra-
tegies (e.g., (Joyce 2005)). There is a growing consensus that the immune
system plays a crucial role in the tumor microenvironment (Bissell and
Radisky 2001; Binnewies et al. 2018;Maman and Witz 2018). In fact,
given the centrality of immune components in the organization of, and
control over, the local tissue, it seems reasonable to say that every cancer
involves the immune system, which necessarily intervenes, at one point or
another, in the shaping of the local context that enables the tumor to emerge,
grow, and perhaps spread.
4.4 Role of the Immune System in the Breakdown
of Biological Individuality That Characterizes Cancer
With all this discussion over the tumor-restricting and tumor-promoting roles
of the immune system in mind, we can now return to the question with which
we started. What exactly is the role of the immune system in the prevention of
the breakdown of individuality that characterizes cancer, and how can the
immune system be involved, conversely, in the decohesion of the biological
individual?
The idea that cancer constitutes a breakdown of biological individuality is
widespread in the scientific and philosophical literature. Biologist Leo Buss was
instrumental in showing that biological individuality in multicellular organisms
must be understood as an outcome of evolution, by which, on several occasions
in life’s history, some cells aggregated and cooperated, and in which emerged
some control mechanisms over cells that would proliferate at the expense of the
whole organism (Buss 1987). Buss takes cancer as an example of a decohesion
of the biological individual, in which cancer cells are“re-individualized”in
a way that becomes harmful to the multicellular organism. This idea has
subsequently been explored by several biologists and philosophers of biology
(Frank 2007; Germain 2012; Plutynski 2018), often inspired by the study of
clonal evolution at the cell level in cancer (Nowell 1976; Greaves and Maley
2012). For example, Godfrey-Smith labels as“de-darwinization”the process by
Philosophy of Immunology 37