In the article title below, can the second colon be replaced with some other punctuation?
Description of the eurotarget cohort: A european collaborative project on targeted therapy in renal cell cancer: Genetic and tumour related biomarkers for response and toxicity
The Chicago Manual of Style, sixteenth edition (2010) addresses this question somewhat obliquely, by limiting its style advice to what it refers to "two subtitles" within a title. After asserting (at 14.97) that "A colon, also italicized, is used to separate the main title from the subtitle," Chicago addresses the situation where a single title appears to have two subtitles:
14.98 Two subtitles. If, as occasionally happens, there are two subtitles in the original (an awkward contingency), a colon normally follows the first and a semicolon the second. The second also begins with a capital [as does the first].
Sereny, Gitta. Cries Unheard: Why Children Kill; The Story of Mary Bell. New York: Metropolitan Books / Henry Holt, 1999.
Although Chicago explicitly frames this advice as a way to handle such titles in a bibliography, there is nothing special about bibliographies that would forbid double colons there but not in regular text.
Chicago doesn't explain its dislike of double colons, but I suspect that the hostility arises involves the lack of clear hierarchical subordination that arises from a title rendered as X: Y: Z. Does the colon after Y indicate that Z is a subtitle of Y and a subsubtitle of X, or is Z on the same footing as Y as a subtitle of X? The colon/semicolon form, X: Y; X, indicates rather more clearly that Y and Z are on an equal footing as subtitles of X—just as in a list, where "the following: X; Y; Z" clearly marshals hierarchically equal-status entries X, Y, and Z. In contrast, "the following: X: Y: Z" is (by normal conventions of punctuation) fatally ambiguous with regard to hierarchical meaning.
Applying the Chicago style recommendation to your title, we get this:
Description of the eurotarget cohort: A european collaborative project on targeted therapy in renal cell cancer; Genetic and tumour related biomarkers for response and toxicity
With regard tog whether the G in Genetic should remain capped, Chicago advises simply that titles treated with sentence-style capitalization should begin "a subtitle" with an initial cap; it doesn't consider whether the subtitle in question is the only one, the first of two, or the second of two:
8.156 Principles and examples of sentence style capitalization. In sentence style capitalization only the first word in a title, the first word in a subtitle, and any proper names are capitalized. ...
From this, I infer that Chicago would approve of capping the G in Genetic in your example.
the eurotarget cohort: a european collaborative project on targeted therapy in renal cell cancer using genetic and tumour-related biomarkers for response and toxicity
I can't recall seeing a title with more than one colon in a carefully edited publication. In the revised example above, the colon indicates that what follows it elaborates on what precedes it. In the recast elaboration, the word "using" removes any need for a second colon in the title.
Thanks again to @sven for suggesting I explain the revised example.
