Atanas Todorov Atanasov's interesting and challenging theory that cells have their own central nervous systems are inspired by Ulam's noöcyte research, and by James Blish's observations of paramecium language skills.
Why ask me?
Because you're a cell. No, I am a Shmoo! Or a character from a Magritte painting! I forget which.

Belated UPDATE. Atanasov's theory accounts for cancer, as a kind of cellular psychopathy that happens when centriole malfunction robs a cell of its sense of rationality and decorum: Things go pear-shaped. This is why the theory featured in the proceedings of the 9th International Conference of Anticancer Research, as published in Anticancer Research journal* [warning, 494 pages].
For completeness it also behooves us to mention Dumitru Pavel's etiology, in which cancer is a kind of protest action provoked by breathing wrong or heartbeating wrong, The unsatisfactory milieu distresses the cells so much that they morph into cancer cells to express their discontent (except when they morph into TB bacteria or HIV virions). Misused heart-muscle cells degenerate into leukemia; chewing wrong provokes epithelial cells into becoming stomach or esophagal cancers; lactating wrong causes breast cancer; not flaring one's nostrils properly while breathing turns cells into lung cancer.
Pavel's publication of his theory-shaped hairball was published, and then retracted from a bottom-feeding mockademic journal (on account of the AIDS denial and TB denial). Pavel further promotes it in comment threads whenever there is a high-profile cancer death, and it has also been pulled from the trash pile and printed as a 17-page letter-to-the-editor in a marginally less skeevy journal faced with a surplus of empty pages.
* Both journal and conferences are not-entirely-mainstream affairs edited and organised by the enthusiastic John G. Delinasios.